The Society of Exploration Geophysicists\
\
MT / EMAP\
Data Interchange Standard

„ 1988, 1991 Society of Exploration Geophysicists. All rights reserved.\
Published 1991. Printed in the U.S.A.

Introduction

In early 1986, representatives from some of the major users of
magnetotelluric (MT) and electromagnetic array profiling (EMAP) data
formed an *ad hoc* committee to investigate a standard for the
interchange and archiving of data. The original committee consisted of
Richard Sigal (Amoco), Truman Holcombe (Standard), Roy Warren (Exxon)
and Joe McNutt (Shell).

By June 1986, the committee produced a first draft describing an
industry-wide standard for the interchange of MT and EMAP data. Over the
course of the next sixteen months, the standard was circulated to a
variety of audiences who deal with MT and EMAP data including oil
company representatives, contractors, and consultants. A draft was
presented to the SEG Technical Standards Committee in November 1986 and
copies were circulated to various reviewers. Also during this time, a
FORTRAN program for reading and writing data in the standard format was
implemented. This proved to be very valuable in uncovering
discrepancies, inconsistencies, and implementation problems prior to
adoption of the standard.

In August 1987, a meeting of the ad hoc committee was held to resolve
the remaining issues and approve a final draft. The resulting draft was
forwarded to Mr Ben Thigpen, chairman of the SEG Technical Standards
Committee, for consideration at the committee's next meeting. After
incorporating minor revisions proposed by the SEG Technical Standards
Committee, the standard was presented to the SEG Executive committee and
was adopted on December 14, 1987.

I would especially like to recognize Richard Sigal of Amoco and Truman
Holcombe of Standard Oil for being major contributors to the MT data
standard project. Although many people contributed to this data
standard, I would like to thank the following persons for providing
valuable comments and criticisms which shaped this document: Karen
Christopherson and Ransom Reddig of Standard Oil, Dwight Eggers of Arco,
Michael Rudder of Exxon, Bob Anderson of Phoenix Geoscience, Arnold
Orange of Emerald Exploration, and Francis Bostick of the University of
Texas.

In late 1990, an effort was begun to produce a revised description which
was easier to use than the original standard. This document, published
in October 1991, is the result of that effort. It is hopefully a
clearer, easier to use description of the original standard. There have
been no changes to the actual standard from the original description
published in December 1987. There have, however, been changes in the
description designed to make the the standard easier to use:

1\. A table of contents has been added, formatting has been improved,
and typographical errors have been corrected.

2\. Typical examples (clearly labeled and enclosed in boxes) have been
added to each block description. Complete EDI examples for stacked
spectra and computed MT parameters have been added as appendices.

3\. Hints (clearly labeled and enclosed in boxes) have been added.
Although not part of the official standard, they offer recommendations
and suggestions regarding use and implementation of the standard.

> David Wight\
> WSE Associates, Inc.\
> 5808 Balcones, Drive Suite 202\
> Austin, Texas 78731 USA
>
> October, 1991

Table of Contents

1.0 Introduction 1

2.0 Purpose and Scope 1

3.0 Organization of Standard 2

4.0 Physical Format and Media 2

4.1 Magnetic Tape and Tape Cartridges 2

4.2 File on Other Media 5

4.3 Data Communications Channel 6

5.0 Geophysical Definitions, Conventions, and Units 6

5.1 Angles, Distances, and Locations 6

5.2 Time Series Data 6

5.3 Power Spectra 7

5.4 Impedances 8

5.5 Apparent Resistivities and Phases 9

5.6 Continuous 1-D Inversion 9

5.7 Signal Amplitude and Coherencies 10

5.8 Parameters Calculated for Surface Impedance Tensor and Tipper 11

5.9 Spatial Filter Parameters 13

5.10 Alternate Processing Techniques 13

6.0 Syntactic Definitions and Conventions 14

6.1 Context-Free Grammars and BNF Notation 14

6.2 Syntactic Definitions 15

6.21 Character Set 15

6.22 Strings and Numbers 16

6.23 Data 16

6.24 Option Lists 17

6.25 Comments 18

7.0 High Level Organization of Data Interchange Files 18

7.1 Overview 18

7.2 \>HEAD Block 19

7.3 \>INFO Block 19

7.4 \>=DEFINEMEAS Section 19

7.5 Data Sections 20

7.51 Time Series Data Sections 20

7.52 Spectra Data Sections 20

7.53 MT Data Sections 21

7.54 EMAP Data Sections 21

7.55 Other Data Sections 22

7.6 \>END Block 22

7.7 \>BNF Representation of an EDI File 22

8.0 Head, Info, Frequency, Zrot, Rhorot, & End Blocks 23

8.1 \>HEAD 23

8.2 \>INFO 25

8.3 \>FREQ 26

8.4 \>ZROT 28

8.5 \>RHOROT 29

8.6 \>END 30

8.7 \>! Comment ! 30

9.0 Measurement Definition Blocks 31

9.1 \>=DEFINEMEAS 31

9.2 \>EMEAS 33

9.3 \>HMEAS 35

10.0 Time Series Blocks 37

10.1 \>=TSERIESSECT 37

10.2 \>TSERIES 39

11.0 Spectra Blocks 40

11.1 \>=SPECTRASECT 40

11.2 \>SPECTRA 42

12.0 MT, EMAP, and Other Section head blocks 44

12.1 \>=MTSECT 44

12.2 \>=EMAPSECT 46

12.3 \>=OTHERSECT 48

13.0 Impedance Data Blocks 49

13.1 \>ZXXR, \>ZXXI, ZXXR.VAR, \>ZXXI.VAR, \>ZXX.VAR, \>ZXX.COV 49

13.2 \>ZXYR, \>ZXYI, ZXYR.VAR, \>ZXYI.VAR, \>ZXY.VAR, \>ZXY.COV 51

13.3 \>ZYXR, \>ZYXI, ZYXR.VAR, \>ZYXI.VAR, \>ZYX.VAR, \>ZYX.COV 53

13.4 \>ZYYR, \>ZYYI, ZYYR.VAR, \>ZYYI.VAR, \>ZYY.VAR, \>ZYY.COV 54

13.5 \>FZXXR, \>FZXXI, \>FZXYR, \>FZXYI 56

14.0 Apparent Resistivity and Phase Data Blocks 58

14.1 \>RHOXX, \>PHSXX, \>RHOXX.VAR, \>PHSXX.VAR 58

14.2 \>RHOXY, \>PHSXY, \>RHOXY.VAR, \>PHSXY.VAR 60

14.3 \>RHOYX, \>PHSYX, \>RHOYX.VAR, \>PHSYX.VAR 62

14.4 \>RHOYY, \>PHSYY, \>RHOYY.VAR, \>PHSYY.VAR 64

14.5 \>FRHOXX, \>FPHSXX, \>FRHOXX.FIT, \>FPHSXX.FIT, 66

15.0 Continuous 1-D Inversion Data Blocks 68

15.1 \>RES1DXX, \>DEP1DXX. RES1DXY, \>DEP1DXY 68

15.2 \>RES1DYX, \>DEP1DYX, RES1DYY, \>DEP1DYY 70

15.3 \>FRES1DXX, \>FDEP1DXX, FRES1DXY, \>FDEP1DXY 72

16.0 Coherency and Signal Data Blocks 74

16.1 \>COH 74

16.2 \>EPREDCOH 75

16.3 \>HPREDCOH 76

16.4 \>SIGAMP 77

16.5 \>SIGNOISE 78

17.0 Tipper Data Blocks 79

17.1 \>TIPMAG, \>TIPPHS, \>TIPMAG.ERR, 79

18.0 Strike, Skew, and Ellipticity Data Blocks 81

18.1 \>ZSTRIKE, \>ZSKEW, \>.ZELLIP 81

18.2 \>TSTRIKE, \>TSKEW, \>TELLIP 82

19.0 Spatial Filter Blocks 83

19.1 \>FILWIDTH, FILANGLE, EQUIVLEN 83

20.0 Non-Standard Data Blocks 84

21.0 Future Extensions 85

Appendix 1 - Terms and Definitions 86

Appendix 2 - Syntax Summary for EDI Files 91

Appendix 3 - Ordering of Data Blocks 93

Appendix 4 - Example EDI File - MT Computed Parameters 94

Appendix 5 - Example EDI File - Stacked Spectra 103

References 108

#  1.0 Introduction

This a description of the proposed data format for electrical
geophysical data approved at a recent meeting of representatives from
several major oil companies who contract for magnetotelluric (MT) and
electromagnetic array profiling (EMAP) data. Its primary purpose is to
facilitate data exchange from contractors to clients and among clients.
It also serves a very important function as a standard format for
archiving data.

The format has been designed to accommodate a wide variety of different
field measurement configurations and processing requirements which might
arise from special applications or new developments. Although very
similar in appearance to some existing formats, it has been slightly
modified to be more consistent, unambiguous, extensible, and realizable.
A number of refinements have been incorporated as a result of actually
implementing the standard.

The format can accommodate any currently used data acquisition
configuration, and has the flexibility to handle any reasonable future
configuration. Supported configurations include single and multi-station
MT, telluric-magnetotelluric (TMT) sounding, EMAP profiling, and
combinations of the above. Provisions have been made for interchange of
data at various levels of acquisition and processing including time
series, power spectra, impedance, and computed parameters including
non-standard parameters. The data interchange file is always an ASCII
file. However, a provision has been made to store actual data values in
a parallel binary data file and reference them through the (ASCII) data
interchange file.

A standard file for the interchange of data from MT, EMAP, or similar
electrical geophysical techniques is called an Electrical Data
Interchange (EDI) file.

#  2.0 Purpose and Scope

This document addresses three separate areas:

*(1) The physical format and media for data interchange.\
(2) Definitions and conventions for representing electrical geophysical
data.\
(3) The syntax and semantics of a data interchange file.*

The first area defines the physical format and media on which data
interchange files may reside. Although the only media currently
specified by the standard is magnetic tape, there are discussions of the
use of non-standard media and data communication channels for data
interchange.

Although the syntax and semantics define the set of characters and bytes
which comprise the data, they do not, for example, define the units for
power spectra or the quadrants for apparent resistivity phase. The use
of a unique data block name for each defined data type assures no
misunderstandings as to the meaning of a given data block. Provisions
have been made for the addition of new data types and for the restricted
use of non-standard data types.

The syntax and semantics of an electrical data interchange (EDI) file
are completely specified by this document in the same way that a
computer language is specified by its manual. In fact, a data
interchange file may be thought of as a program written in a "data
interchange programming language" as defined in this document. A program
which reads data interchange files and converts the data into a usable
form is very analogous to a compiler.

#  3.0 Organization of Standard

Section 4 defines the physical format and media on which EDI files may
reside. Specifically, it defines the use of magnetic tape, the only
currently standardized media. It also discusses the use of non-standard
media and data communication channels.

In Section 5 units and conventions are defined for the geophysical
quantities which may be represented within an EDI file.

Section 6 first introduces the concept of a context-free grammar and the
BNF (Backus-Naur form) notation. This notation will be used in later
sections to define the syntax of an EDI file. The section then uses this
notation to define a series of constructs which will be the basic
constituents of our syntactic definition.

Section 7 provides a high level syntactic and semantic overview of an
EDI file. First, it introduces the concepts of data blocks and data
sections. Then, it briefly discusses how an EDI file is made up of a
Head block, an Info block, a measurement definition section, one or more
data sections, and an end block.

Sections 8-20 of the standard provide detailed descriptions of all of
the types of data blocks from which EDI files are made. The definitions
for data blocks are grouped such that several blocks all having the same
characteristics are defined in one place. Each definition includes (1) a
list of the data blocks and a brief description of each, (2) a
description of the restrictions regarding where in an EDI file the
block(s) may appear, (3) a list of options which may be used with the
block(s), (4) restrictions on the data set which may be part of the data
block, and (5) any other notes regarding the use of the block(s).

Section 21 describes the mechanism for orderly evolution of this
standard.

Appendix 1 contains a list of terms and definitions used within this
document. Many terms used throughout this document are explained here.
It is recommended that this list be read prior to reading the main text
of the standard.

Appendix 2 contains a complete summary of the syntax for an EDI file
using BNF notation.

Appendix 3 is a diagram summarizing the ordering of data blocks within
an EDI file.

Appendices 4 and 5 contain complete example files for MT computed
parameters and stacked spectra respectively.

The Reference section lists the sources for the geophysical conventions
embraced by this standard.

#  4.0 Physical Format and Media

##  4.1 Magnetic Tape and Tape Cartridges

At the present time, the only universal media is still 9 track 1/2\"
magnetic tape. This is the only standard media for electrical data
interchange. Tapes must meet the specifications set forth in ANSI
standard for unrecorded information interchange X3.40-1976.

The IBM 3480 tape cartridge is rapidly gaining acceptance as a standard
media. Therefore, it is also acceptable as an an interchange media. If
this media is used, it is to be organized in the same manner as a
magnetic tape.

The preferred and recommended media and format for the interchange and
archival of electrical geophysical data is:

\(1\) 1/2\" magnetic tape recorded at 1600 characters per inch (CPI)
using phase encoding (PE) as specified by ANSI X3.39-1973

The standard, however, allows use of the following alternative media and
formats if they are more appropriate:

\(2\) 1/2\" magnetic tape recorded at 800 characters per inch (CPI)
using non-return-to-zero inverted (NRZI) encoding as specified by ANSI
X3.22-1973.

\(3\) 1/2\" magnetic tape recorded at 6250 characters per inch (CPI)
using group -coding as specified by ANSI X3.54-1976.

\(4\) IBM 3480 compatible 1/2\" tape cartridge recorded as specified by
ANSII X3B5 (Draft 7 or later) "Proposed Standard for Recorded Magnetic
Tape and Cartridge for Information Interchange".

Whichever format and media are used, they must comply with the
corresponding ANSI standard and must be clearly labeled as to which
recording format was used for recording. These are standard formats and
drivers for reading and writing tapes in these formats are provided on
most computer systems. Copies of the ANSI standards cited above are
available from:

American National Standards Institute\
1430 Broadway\
New York, N.Y. 10018

Many computer systems support a flexible record structure and method of
writing labels and organizing data on magnetic tapes. Many are unique to
a particular computer system. The most available system independent
format is the ANSI Standard for Magnetic Tape Labels and File Structure
for Information Interchange (X3.27-1978). Although such tape
organizations are more versatile, they are not necessary for the
exchange of EDI data.

This data interchange standard requires only the following very simple,
"least common denominator" record structure and data organization. Tapes
written in the following manner can be read or written by almost any
computer system. Such tapes are often referred to as "unlabeled tapes".
Most computer systems will provide a "Read/Write Foreign Tape" utility
which can read and write tapes in the above format. If such a utility is
not available, its simple structure allows a special driver to be
written with a minimal effort.

Logical records must always be exactly 80 bytes in length. Space
characters (ASCII 32) should be used to pad records. No explicit
delimiters such as carriage returns or linefeeds are to be used.
Physical records (or blocks) are to always be exactly 2000 bytes. Tapes
may be 600, 1200 or 2400 feet as appropriate for the data set.

The first file on the tape, immediately after the beginning of tape
(BOT) mark, will be a tape header file. This will be followed by one or
more EDI files. There will be exactly one end-of-file mark \<EOF\>
between files and two end-of-file \<EOF\> marks after the last data
interchange file on the tape. The overall tape layout is as follows:

Leader

\<BOT\>

Tape Header File

\<EOF\>

Electrical Data Interchange File 1

\<EOF\>

Electrical Data Interchange File 2

\<EOF\>

\...

Electrical Data Interchange File

\<EOF\>

\<EOF\>

Unused tape

\<EOT\>

Trailer

The contents of the tape header file are not in a fixed format. The
header must contain legal ASCII characters (see Sections 6.21, 6.22)
which convey all of the following information in a form which is clear
and understandable to a person who does not have prior knowledge of the
contents of the tape.

\(1\) Name and address of the creator of the tape.

\(2\) Date tape was generated.

\(3\) Computer system on which tape was generated and format
information.

\(4\) Description of data on the tape.

\(5\) List of file numbers with a brief description of the contents of
that file.

\(6\) If parallel binary data files are included (see Section 6.23),
appropriate information must be included to uniquely associate each
binary file with the corresponding EDI file.

**Example Tape Header File:**

Tape Created by: BIG OIL Geophysics

8108 Mesa Drive

Austin, Texas

Tape Creation Date: March 19, 1987

Tape Created Using: Hewlett-Packard 9000/320 computer

Hewlett-Packard 7974A tape drive

1600 BPI PE. Rec size = 2000 bytes

This tape contains MT data for the BLEAK prospect in Nolan County,
Texas. The data was acquired by Big Oil Geophysics from August 1-Sept
15, 1986. The MT survey consists of 3 lines of MT sites - A, B, and C.
For each line, there is an EDI file containing stacked spectra and a
separate EDI file containing computed MT parameters.

This tape contains 7 files as follows:

File Number Description

1 This tape directory file

2 Stacked Spectra - Line A (21 sites)

3 MT Parameters - Line A (21 sites)

4 Stacked Spectra - Line B (15 sites)

5 MT Parameters- Line B (15 sites)

6 Stacked Spectra - Line C (28 sites)

7 MT Parameters - Line C (28 sites)

##  4.2 File on Other Media

Even though magnetic tape and IBM 3480 compatible tape cartridges are
the only media specified in this standard, many contractors and oil
companies have computer systems which can exchange files using other
media. Often the use of other media is more efficient than the use of
magnetic tape. By mutual agreement, other media may freely be used for
the exchange of EDI files. The device drivers which read and write
logical records must, of course, use the same conventions for separation
of records. Regardless of the media, the size of a logical record is not
to exceed 128 bytes.

Once again, we point out that an EDI file is analogous to the source
code file for a program. Its contents do not depend on the physical
media or any file system organization on which it resides. Its meaning
depends only upon the characters within the file which are organized
according to a fixed set of rules.

For archival purposes, however, 9 track 1/2\" magnetic tape recorded at
1600 BPI is the only allowed media.

**Hints:** 1. DOS format floppies have become widely accepted for the
exchange of EDI data. A single high-density 3 1/2\" floppy disk can hold
an EDI file containing stacked spectra or computed parameters for
several sites. Another widely accepted media is the quarter inch data
tape cartridge written in one of the QIC standard formats. The use of
such media for the exchange of data is acceptable so long as both
parties agree on the format.

2\. Note that the directory structure required for 1/2\" nine-track
magnetic tape is not required when the media format supports its own
directory structure. It is recommended, however, that such media include
a README file describing the files on the media.

3\. Note also that all of the 2000 byte blocks, blank padding, etc.
specified for 1/2\" nine-track magnetic tape do not apply to other
media. These media simply use text files to hold the data.

3\. Although the standard allows record (line) lengths up to 128
characters, it is highly recommended that line lengths be limited to 80
characters so they can be easily viewed and edited on all PC\'s and
terminals.

4\. For MT data, the recommended deliverable is one EDI file containing
a spectra section (\>=SPECTRASECT) with stacked spectra for each site in
the survey, and a second EDI file containing an MT section (\>=MTSECT)
for each site in the survey. In this case, the head, info, and
measurement definition sections would be identical for the two EDI
files.

5 If the survey is greater than 25 or 30 sites, it is appropriate to
break these into multiple EDI files, for example one for each line. If
multiple EDI files are used to hold all of the sites in a survey, the
site id\'s and measurement id\'s should be unique across all of the EDI
files for the survey.

6\. Sometimes the contractor delivers EDI files to the customer on a
daily basis as data is acquired. In this case, each EDI file may contain
stacked spectra or computed parameters for only the sites in that day\'s
run. In this case, the site id\'s and measurement id\'s should be unique
across all of the EDI files for the survey.

##  4.3 Data Communications Channel

The exchange of EDI files need not be limited to physical media. Most
computer systems now support the exchange of files over data
communication links. EDI files can be transmitted from one computer to
another using a mutually agreed upon protocol. It is highly recommended
that any protocol used for the transmission of EDI files include a
mechanism for error checking. As with physical media, the logical record
length is not to exceed 128 bytes.

#  5.0 Geophysical Definitions, Conventions, and Units

##  5.1 Angles, Distances, and Locations

All azimuthal angular measurements are in degrees. Absolute angles, such
as those in the measurement definition section, are relative to true
north. Positive angles represent clockwise rotation and negative angles
represent counterclockwise rotation. Angles are always to be reduced to
the range of -180 degrees to +180 degrees. Note that impedance phase
angles (see Section 5.5), however, are always measured counterclockwise
in the complex plane.

The default units for lengths and distances are meters. However, any
data block which specifies lengths or distances will include a UNITS=
option. Use of the UNITS=FT option indicates that lengths and distances
within that block are in feet rather than meters.

Absolute locations are expressed in terms of latitude, longitude,
elevation, and (optionally) a brief textual description. Latitudes and
longitudes are expressed as DEG:MIN:SEC. North and East are considered
positive and South and West are considered negative. Elevations are
relative to sea level with positive being upward. Unless the UNITS=FT
option is specified, elevations are in meters. The recommended accuracy
for latitudes and longitudes (for typical latitudes) is .01 seconds.
Textual descriptions might refer to an intersection of two roads, or
some other landmark.

##  5.2 Time Series Data

Because of the system dependent nature of data acquisition, there are no
standard units for time series data. Generally, units are integers
representing raw data before system response has been removed. If time
series data sections are included within an EDI file, a full explanation
of the nature of the data MUST be included within the \>INFO section.
This explanation should adequately describe the response of the
measurement and recording system used for acquiring the data.

Because of the tremendous data volume, and its system dependent nature,
time series data are not usually included with delivered data. It is
only delivered when special reprocessing requirements preclude the use
of another form of the data such as power spectra.

**Hints:** 1. Although this standard provides a framework for the
delivery of time series data in a standard format, the standard is not
sufficiently specific to assure data interchangability.

2\. For data interchange of time series data, it is necessary that both
contractor and customer agree on the specifications for the data to be
delivered.

3\. For data archive of time series data, the INFO section must
completely and accurately describe the data being delivered.

##  5.3 Power Spectra

Average power spectra estimates are often used to represent "raw" MT or
EMAP data. Because most processing is done in the frequency domain, they
are a convenient representation, and are much more compact than time
series.

Power spectra are to be expressed in terms of standard units. Auto and
cross power spectra for two electric field measurements are to be in
units of . Auto and cross power spectra for two magnetic field
measurements are to be in units of . Cross power spectra for mixed
measurements are to be in units of . All spectra are to be normalized
for system response and number of samples. Unless specified otherwise by
the ROT option, they are assumed to correspond to the measurement
directions as defined in the \>DEFINEMEAS section.

A \>SPECTRA data block contains estimates of all the auto and cross
power spectra for a set of measurements for a given frequency and
bandwidth. These average spectra estimates are the result of averaging a
number of independent spectra estimates. They may be independent in time
(e.g. cascade decimation), or in frequency (e.g. FFT), or a combination.
These data blocks usually represent the final averages, although the
SEGNUM option allows delivery of smaller segments also.

**Hints:** 1. Stacked spectra are a good way to deliver "raw" data which
may be reprocessed at a later time using alternative processing
algorithms. Even if computed parameters are delivered, it may be a good
idea to also deliver spectra. Because stacked spectra are a compact
representation of the "raw" data, they are often the preferred way of
delivering unprocessed data.

2\. It may be desirable to also have the individual spectra segments
prior to stacking. This allows re-stacking of the data at a later time,
perhaps resulting in higher data quality. If spectra segments are
delivered, it is recommended that they be in addition to final stacked
spectra and that they be delivered in a separate EDI file.

##  5.4 Impedances

For tensor MT the surface impedance tensor has four components: Z, Z, Z,
and Zwhich satisfy the impedance relations:

E= ZH+ ZH\
E= ZH+ ZH

For EMAP, where only one component of the electric field is measured, it
has only two: Zand Zwhich satisfy the impedance relation:

E= ZH+ ZH

It is possible to compute the 4 MT impedance tensor estimates (Z, Z, Z,
Z) from a set of spectra (in a least-squares sense), in a number of ways
depending upon the reference fields used. The reference measurements (R,
R) may be local or remote. For EMAP, impedances may be computed using
the H component parallel to the line (Z) and using the H component
perpendicular to the line (Z). For synthetic modeling applications, only
Zxy may be required. However, in field acquisition where the line is not
completely straight, both impedances must be provided.

For both MT and EMAP data, the option list for the data section will
give the electric and magnetic field measurements from which the
impedances were computed along with the reference measurements used.
Impedances are normally assumed to be least-squares estimates using
either local or remote reference measurements. In this case, 6
measurement ID's - Ex, Ey, Hx, Hy, Rx, and Ry must be specified. If
another estimation technique has been used (such as L1 norm or averaging
several least-squares estimates) it should be indicated using the TYPE
option.

Unless specified otherwise by the ROT option, the impedances are assumed
to be computed for the measurements in the measurement directions as
defined in the \>DEFINEMEAS section.

To allow reprocessing of tensor MT data from impedance estimates, the
real and imaginary parts of all four impedances should be delivered.
Although they may be provided in the measurement directions, it is often
more convenient to rotate all of the impedances to either true north or
to the strike angle. In the first case the ROT option should specify
ROT=NORTH. Alternatively, a \>ZROT data block may be included which
indicates the rotation angle for each frequency relative to true north,
and the ROT option should specify ROT=ZROT.

For EMAP data, the real and imaginary parts for the in-line and
perpendicular impedances: ZXX and ZXY, should always be delivered. The
spatially filtered impedances, FZXX and FZXY, should also be delivered.
Because EMAP impedances are assumed to correspond to the measurement
directions, the default ROT option (ROT=NONE) should always be used.

In order to provide rigorous error estimates for the surface impedance
tensor elements, one must calculate the variance for the real part, the
variance for the imaginary part, and a covariance. This is done in the
usual manner for a finite number of estimates of the real and imaginary
parts, which are clearly independent functions. This defines an error
"ellipse" about the impedance tensor element in the complex plane. The
\>Z\*\*R.VAR, \>Z\*\*I.VAR, and \>Z\*\*.COV (where \*\* is XX, XY, YX,
or YY) keywords are provided for the real variance, imaginary variance,
and covariance, respectively, for each tensor element. (Section 13.0).

However, the usual practice is to calculate a simplified "variance" as
defined by Gamble, 1978, pp. 66-72. This is a real number (an estimate
of the average of the variances of the real and imaginary parts) that is
the radius of a circle about the tensor element in the complex plane.
This circle approximates the error ellipse and for most purposes is an
adequate estimate of the statistical uncertainty. The \>Z\*\*.VAR
keyword is provided (Section 13.0) for this parameter. This is typically
the only error estimate provided for impedance tensor components.

##  5.5 Apparent Resistivities and Phases

Apparent resistivities are given as:

> ρ= $\frac{\left| Z_{\text{ij}} \right|^{2}}{\text{wm}}$ i, j = x, y

(where m is the permeability of free space and w is the frequency in
radians), and are in units of W‑meters.

The impedance phases are given by:

> φ= tan
> ${}^{\text{-1}}\left( \frac{\text{ Im }\left\{ \text{ Z}_{\text{ij}} \right\}}{\text{ Re }\left\{ \text{ Z}_{\text{ij}} \right\}} \right)$
> i, j = x, y

and are in degrees measured counterclockwise from the positive real axis
in the complex plane. A homogeneous earth requires E and H fields to be
in phase. The in-phase condition becomes +45 degrees for Zand -135
degrees for Zfor generally accepted sign conventions for E and H. Note
that this differs from the convention followed for azimuthal angles as
specified in Section 5.1.

Unless specified otherwise by the ROT option, the impedances are assumed
to be computed for the measurements in the measurement directions as
defined in the \>DEFINEMEAS section.

To allow reprocessing using alternative rotations of apparent
resistivities for tensor MT data, the apparent resistivity magnitudes
and phases computed from all four tensor impedances should be included.
Although they may be delivered in the measurement directions with no
\>RHOROT data block included, it is often more convenient to rotate all
of the apparent resistivities to either true north or to the strike
angle. In the first case the ROT option should specify ROT=NORTH.
Alternatively, a \>RHOROT data block may be included which indicates the
rotation angle for each frequency relative to true north, and the ROT
option should specify ROT=RHOROT.

In cases where no reprocessing is anticipated, a two-dimensional model
is sometimes assumed and the apparent resistivities are rotated such
that Rhois parallel to the geological strike (or to another agreed upon
angle) and Rhois perpendicular. In this case, Rhoand Rhoare assumed to
be negligible and are not included.

For EMAP data, the apparent resistivity magnitudes and phases derived
from the impedances computed from the parallel H component (Rhoand Phs),
and from the perpendicular H component (Rhoand Phs) should be delivered.
The apparent resistivity magnitude and phase from the corresponding
spatially filtered impedances: FRho, FPhs, FRho, and FPhs, should also
be delivered.

##  5.6 Continuous 1-D Inversion

Continuous, one-dimensional inversions can be computed from apparent
resistivity data sets. The Bostick inverse is the most common. A
continuous inverse consists of two data sets. One record must contain a
set of values representing depths which are strictly increasing. The
units for the depths are meters unless the UNITS option specifies
UNITS=FT. The second record contains a set of resistivity values which
correspond one-to-one with the depth values. It is always in units of
W-meters.

Any continuous inversion data blocks in a data section are assumed to be
derived from the preceding apparent resistivity data blocks. If this is
not true, it should be clearly indicated in the \>INFO section. Unless
specified otherwise by the ROT option, the inversions are assumed to be
computed for the measurements in the measurement directions as defined
in the \>DEFINEMEAS section.

For tensor MT data, continuous inversions may be delivered for up to
four apparent resistivities, although inversions for only RHOXY and
RHOYX are usually included. For EMAP data, continuous inversions for the
apparent resistivities computed from both the unfiltered and spatially
filtered perpendicular impedance (RES1DXY, DEP1DXY, FRES1DXY, and
FDEP1DXY) should be delivered. Optionally, continuous inversions for the
apparent resistivities computed from both the unfiltered and spatially
filtered parallel impedance (RES1DXY, DEP1DXX, FRES1DXX, and FDEP1DXX)
may also be delivered.

The TYPE option should clearly indicate the technique used for
inversion. If additional explanation is indicated, it should be in the
\>INFO section. For Bostick inversion, the type should indicate whether
the apparent resistivity amplitudes (TYPE=BOSTICK-AMP) or Hilbert
transform of the phase (TYPE=BOSTICK-PHS) data was used for estimating
the slopes used in the inversion.

##  5.7 Signal Amplitude and Coherencies

The signal amplitude and coherencies are used in evaluating data
quality, and identifying the source(s) of noise in the data. For
identifying the source(s) of noise in the data it is most useful to have
these parameters in the direction of the acquisition sensors, and for
evaluating data quality it is most useful to have these parameters in
the direction of the apparent resistivities. The orientation of these
parameters can be specified using the ROT option. This option may be
ROT=NONE, meaning that the parameters correspond to the measurement
directions, ROT=RHOROT, meaning that the parameters correspond to the
rotation angles given in the \>RHOROT block, or RHO=NORTH, meaning that
the parameters have been rotated to true north. The default is ROT=NONE.

The signal amplitude or power spectral density for any measurement can
be delivered using a SIGAMP data block. The signal level may be useful
in diagnosing poor data. The default for SIGAMP data is amplitude
spectra. However, the option AMPPWR=PWR can be used to provide
auto-power spectra instead. The units are the same as those for
\>SPECTRA data blocks (see Section 5.3), except, of course, for the
appropriate amplitude/power conversion. The EUNITS or HUNITS option (as
appropriate) may be used to specify the units if other than the default.

The signal amplitude (or power spectral density) can either be
calculated from the total field (including the noise amplitude) or
estimated using a remote field to eliminate the noise amplitude (Gambel,
1978). The default for the signal amplitude is the total field; however,
the option TYPE=SIGNAL or TYPE=NOISE can be used to deliver the
estimated signal or estimated noise.

For any two measurements A and B (in the temporal frequency domain), the
coherency between A and B is defined as:

> COH = $\frac{|\text{ <A B*> }|^{2}}{\text{<A A*>  <B B*> }}$

A and B are commonly the orthogonal electric and magnetic fields.

One can use an estimate of the impedance tensor to compute predicted
E's, PEand PE, from the measured H's as:

> PE= ZH+ ZH\
> PE= ZH+ ZH

In a similar manner, one can use an estimate of the admittance tensor to
compute predicted H's, PHx and PHx from measured E's:

> PH= YE+ YE\
> PH= YE+ YE

The E-predicted coherency can be computed using the predicted E and the
orthogonal measured H, or an H-predicted coherency can be computed using
the predicted H and measured E.

##  5.8 Parameters Calculated for Surface Impedance Tensor and Tipper

The impedance principal direction or "strike" (see \>ZSTRIKE in Section
18.0) can be defined in many ways. For example it can be defined as the
angle which:

1\) Maximizes \|Z${}_{\text{xy}}^{©}\text{  }$+
Z${}_{\text{yx}}^{©}$\|${}^{2}$,

2\) Maximizes
\|Z${}_{\text{xy}}^{©}$\|${}^{2}\text{  }$+\|Z${}_{\text{yx}}^{©}$\|${}^{2}$,

3\) Minimizes
\|Z${}_{\text{xx}}^{©}$\|${}^{2}\text{  }$+\|Z${}_{\text{yy}}^{©}$\|${}^{2}$,
or

4\) Minimizes \|Z${}_{\text{xx}}^{©}\text{  }$+
Z${}_{\text{yy}}^{©}$\|${}^{2}$;

where Z, Z, Z, and Zare the impedances rotated to the impedance strike
angle. The principal direction, A, may be determined by incrementally
rotating the impedance tensor, or alternatively it may be calculated
analytically from the maximization of \|Z${}_{\text{xy}}^{©}\text{  }$+
Z${}_{\text{yx}}^{©}$\|as:

> A = \* tan
> ${}^{\text{-1}}\left( \frac{\text{2R}_{1}\text{*R}_{2}\text{+I}_{1}\text{*I}_{2}}{R_{1^{2}}\text{+I}_{1^{2}}\text{-R}_{2^{2}}\text{-I}_{2^{2}}} \right)$
>
> where R1 = Re
> $\left\{ \text{ Z}_{\text{xx}}\text{ - Z}_{\text{yy}} \right\}$,\
> I1 = Im
> $\left\{ \text{ Z}_{\text{xx}}\text{ - Z}_{\text{xy}} \right\}$,\
> R2 = Re
> $\left\{ \text{ Z}_{\text{xy}}\text{ + Z}_{\text{yx}} \right\}$,\
> and I2 = Im
> $\left\{ \text{ Z}_{\text{xy}}\text{ + Z}_{\text{yx}} \right\}$,

or from an eigenstate formulation (Eggers, 1982) (Section 5.10). For a
perfect two-dimensional earth, the same angle will satisfy all of these
relationships. In actual field data, typically a three-dimensional
anisotropic environment, the different methods produce different
principal directions. However, in most interpretable situations they are
not significantly different. There is an inherent 90 degree ambiguity in
the calculated principal directions which can only be resolved by
interpreting the off-diagonal element ( Zor Z) of the rotated impedance
tensor best represents the E-parallel (TE) mode and which the
E-perpendicular (TM) mode. In practice, this is sometimes attempted by
the field data acquisition crew, but more often is an interpretation
task done after the fact. In any case, the method used to calculate the
principal directions and resolve its ambiguities (if attempted) should
always be documented or referenced in the \>INFO text.

The impedance skew (See \>ZSKEW in Section 18.0) is usually defined as

> ZSKEW =
> $\frac{\left| Z_{\text{xx}}^{©}\text{ + Z}_{\text{yy}}^{©} \right|}{\left| Z_{\text{xy}}^{©}\text{ - Z}_{\text{yx}}^{©} \right|}$

where Z, Z, Z, and Zare the rotated impedance elements. Any departure
from this definition should be documented in the \>INFO text.

The impedance ellipticity (See \>ZELLIP in Section 18.0) is usually
defined as

> ZELLIP =
> $\frac{\left| (Z_{\text{xx}}\text{-Z}_{\text{yy}})\text{ * cos }(\text{2A})\text{ + }(Z_{\text{xy}}\text{+Z}_{\text{yx}})\text{ * sin }(\text{2A}) \right|}{\left| (Z_{\text{xy}}\text{+Z}_{\text{yx}})\text{ * cos }(\text{2A})\text{ + }(Z_{\text{xx}}\text{-Z}_{\text{yy}})\text{ * sin }(\text{2A}) \right|}$

where A is the calculated impedance principal direction. Any departure
from this definition should be documented in the \>INFO text.

The complex tipper components, Tx and Ty, satisfy the tipper relation:

> Hz = TH+ TH

The tipper relation above may be solved for Tx and Ty using either local
or remote reference fields, Rx and Ry, as in the impedance case. Thus,
the computation of the tipper parameters, Tx and Ty (in a least-squares
sense) can be described by specifying 5 measurements: Hx, Hy, Hz, Rx,
and Ry, where Rx and Ry may be coincident with Hx and Hy (local
reference) or may be other measurements (remote reference).

From Tx and Ty, the tipper magnitude and tipper phase can be defined as:

> TIPMAG = $\sqrt{|\text{Tx}|^{2}\text{ + }|\text{Ty}|^{2}}$
>
> TIPPHS =
> $\frac{|\text{Tx}|^{2}\text{ * Phs}(\text{Tx})\text{ + }|\text{Ty}|^{2}\text{ * Phs}(\text{Ty})}{|\text{Tx}|^{2}\text{ + }|\text{Ty}|^{2}}$

In a manner similar to the impedance principal direction, the tipper
principal direction (see \>TSTRIKE in Section 18.0) can be defined as
the angle which:

> \(1\) Minimizes \|T \'\|\
> (2) Maximizes \|T \'\|or\
> (3) Maximizes \|T \'\|+ \|T \'\|

where T \'x and T \'y are the tipper components rotated to the tipper
strike angle. However, this method has the same 90 degree ambiguity as
the impedance principal direction defined earlier. An alternative,
preferred method for defining the tipper principal direction, B, is
given by Jupp and Vozoff, 1976:

> B =
> $\frac{(\text{TxR}^{2}\text{+TyR}^{2})\text{ * tan}^{\text{-1}}\left( \frac{\text{TyR}}{\text{TxR}} \right)\text{ + }(\text{TxI}^{2}\text{+TyI}^{2})\text{ * tan}^{\text{-1}}\left( \frac{\text{TyI}}{\text{TxI}} \right)\text{ + 90}}{|\text{Tx}|^{2}\text{ + }|\text{Ty}|^{2}}$

where TxR, TxI, TyR, and TyI represent the real and imaginary parts of
Tx and Ty respectively, and B is measured clockwise from true north in
the defined azimuthal coordinate system. This is the angle which
maximizes the coherency between the vertical and horizontal magnetic
field. It has an inherent ambiguity of plus or minus 180 degrees.
However, one can choose the principal direction for which the phase of
COH(H\'z,H\'x) (the coherency between the vertical magnetic field, Hz,
and the horizontal field component, Hx, rotated to the chosen principal
direction) falls between +90 degrees and -90 degrees from the real axis
in the complex plane.

The tipper principal direction defined in this way is unambiguous for a
perfect two-dimensional earth, that is, it always points toward the
resistive side of the contact which induces the vertical magnetic field
component. The preferred definition of keyword \>TSTRIKE is then B plus
90 degrees. Again, the method for determining tipper strike should
always be documented or referenced in the \>INFO text.

##  5.9 Spatial Filter Parameters

The width of the spatial filters used for EMAP processing can be
delivered for examination or for use in reprocessing. A filter parameter
represents the length of a spatial filter which is applied to the
impedances. This filter length may be expressed in terms of distance
units (FILWIDTH) or in terms of equivalent dipole lengths (EQUIVLEN).
For a non-straight EMAP line, a filter angle (FILANGLE) is also
required.

##  5.10 Alternate Processing Techniques

Alternative methods for computation of apparent resistivities have been
presented by Eggers (1982) and LaTorraca (1986). Data to be delivered if
using these methods includes eigenvalues, principal axis directions for
eigenvectors, eigenvectors (complex), appropriate ellipticities, skews,
and the apparent resistivities corresponding to the eigenvalues.

Although no data blocks have been provided for this information, .EXP
blocks can be used to deliver all of these parameters. The use of .EXP
blocks should always be fully documented in the \>INFO text.

#  6.0 Syntactic Definitions and Conventions

##  6.1 Context-Free Grammars and BNF Notation

For the syntactic specification of a data interchange file, we shall use
a notation called a context-free grammar (or grammar, for short). This
is also called a BNF (Backus-Naur Form) description. This notation has
been borrowed from the designers of programming languages (Aho and
Ullman, 1978). It has a number of advantages as a method of syntax
specification:

\(1\) A grammar gives a precise, yet easy to understand, syntactic
specification.

\(2\) An efficient parser can be constructed automatically from a
properly designed grammar. Certain parser construction processes can
reveal syntactic ambiguities and other difficult to parse constructs
which might otherwise go undetected in the initial specification of the
syntax.

\(3\) A grammar imparts a structure to a syntax that is useful for its
translation into a usable form and for the detection of errors.

In general, our grammar is constructed from terminals, nonterminals, and
productions. The basic elements which comprise our data interchange file
are ASCII characters. These are our terminals. Nonterminals are special
symbols such as \<integer\> which denote a set of particular terminals
arranged in a particular way. Productions define the ways in which
nonterminals may be built up from one another and from terminals.

The following symbols are meta-symbols belonging to the BNF formalism,
and are not symbols (unless explicitly noted) in our syntax definition:

"A" A character inside of double quotes represents that ASCII character.

/nnn A slash followed by 3 decimal digits represents the ASCII character
with the character code nnn. This is generally used for non-printing
characters.

" " Two double quotes denote the empty terminal symbol, i.e., no
character.

\<string\> A string enclosed in \< \> denotes a nonterminal.

::= Two colons and an equal defines a production. Read it as "is defined
as".

\| A vertical bar means "or".

"A".."Z" Two characters, specified by either of the two conventions
above, separated by two periods is a shorthand notation for any one of
the characters in the indicated range. (e.g. "A".."Z" ::= "A" \| "B" \|
\... "Y" \| "Z" )

{ } A pair of curley brackets denote the repetition of the enclosed
symbols zero or more times.

{ }+ A pair of curly brackets followed by a plus denote repetition of
the enclosed symbols one or more times.

( ) Parentheses may be used to indicate precedence. Normally,
concatenation (ordering) has the highest precedence, followed next by
\|, then finally { } and { }+, all being evaluated left to right.

##  6.2 Syntactic Definitions

###  6.21 Character Set

The following productions divide all of the 256 possible values for an 8
bit ASCII character code into various character sets. The nonterminals
defined here will be used in later productions.

\<upc_letter\> ::= "A" .. "Z"

\<lwc_letter\> ::= "a" .. "z"

\<digit\> ::= "0" .. "9"

\<special\> ::= "\>"

\<other\> ::= "!" \| " \' " \| "#" \| "\$" \| "%" \| "&" \| "(" \| ")"
\|\
"\*" \| "+" \| "," \| "-" \| "." \| "/" \| ":" \| ";" \| "\<" \|\
"=" \| "?" \| "@" \| "\[" \| "\\" \| "\]" \| "\^" \| "\_" \| " \" " \|\
"{" \| "\|" \| "}" \| "\~"

\<space\> ::= " "

\<null\> ::= /000 \| /010 \| /013

\<illegal\> ::= /001 .. /009 \| /011 .. /012 \| /014 .. /031 \|\
/127 .. /255

Alternatively, we could have used the /nnn form to represent all of our
sets:

\<upc_letter\> ::= /065 .. /090

\<lwc_letter\> ::= /097 .. /122

\<digit\> ::= /048 .. /057

\<special\> ::= /062

\<other\> ::= /033 .. /047 \| /058 .. /061 \| /063 .. /064 \|\
/091 .. /096 \| /123 .. /126

\<space\> ::= /032

\<null\> ::= /000 \| /010 \| /013

\<illegal\> ::= /000 .. /009 \| /011 .. /012 \| /014 .. /031 \|\
/127 .. /255

Spaces (/032) are preserved as data are read. Spaces may serve as
delimiters, be used to enhance readability, or can be used to pad
logical records.

The syntax of an EDI file is based only upon a stream of characters,
neither physical nor logical records have syntactic significance. The
mechanism for separating both physical and logical records is
implemented by the system's device drivers. No other explicit record
terminators are to be added when writing an EDI file. With the exception
of three characters described below, only printing characters may be in
EDI files.

For magnetic tape (Section 4.1) or any other media (Section 4.2), the
system device drivers define the mechanism for record separation. The
mechanism used by the system for record separation should be transparent
to an application program which simply calls the system's read and write
record routines.

However, because different computer systems may be used for reading and
writing interchange files, the device drivers could fail to remove all
of the record separators. Carriage return (/013) and linefeed (/010)
characters (sometimes used by systems as logical record separators)
could in some cases appear as part of the data. In like manner, ASCII
null (/000) characters (sometimes used for padding physical records)
could in some cases appear as part of the data.

Therefore, the three ASCII characters: carriage return, linefeed, and
null are tolerated within the data but are to be completely ignored. The
presence of any other non-printing ASCII characters within an EDI file
is considered to be an error.

###  6.22 Strings and Numbers

We can simply define nonterminals for strings, numbers, and other simple
syntactic constructs as follows:

\<letter\> ::= \<upc_letter\> \| \<lwc_letter\>

\<legal_char\> ::= \<letter\> \| \<digit\> \| \<other\>

\<unsign_int\> ::= { \<digit\> }+

\<unsign_real\> ::= \<unsign_int\> "." \<unsign_int\> \| \<unsign_int\>
"." \| "." \<unsign_int\>

\<sign\> ::= "+" \| "-"

\<int\> ::= ( \<sign\> \| " " ) \<unsign_int\>

\<real\> ::= ( \<sign\> \| " " ) \<unsign_real\>

\<exp\> ::= \<real\> "E" \<int\>

\<string\> ::= { \<legal_char\> }+ \| ( " \" " { \<legal_char\> \| " " }
" \" " )

\<number\> ::= \<int\> \| \<real\> \| \<exp\>

\<date\> ::= \<digit\> \<digit\> "/" \<digit\> \<digit\> "/" \<digit\>
\<digit\>

\<lat_long\> ::= \<int\> ":" \<unsign_int\> ":" ( \<unsign_int\> \|
\<unsign_real )

###  6.23 Data

Blocks of data values may be represented with one of two forms:

\(1\) An ASCII data set consists of the characters "//", followed by a
count, followed by a set of data values. The count and all data values
are represented by textual representations for \<number\>. (Section
6.22).

\(2\) A Binary data set is represented in an EDI file by one of three
special sets of characters which mean "read binary data from the current
position in the open binary data file". The three special character sets
"/I/", "/R/", and "/D/" corresponding to the three forms of binary data:
INTEGER (two's complement 16 bit integers), REAL (IEEE format 32 bit
reals), and DOUBLE (IEEE format 64 bit reals).

An ASCII data set begins with two slash characters, "//". This is
followed by a count, and then the actual data values. The count is an
integer in the range 0 to 32767. A count of zero means that the data set
is empty. The number of data values must be EXACTLY the same as the
count. Any or all of the data values may be represented with a special
value meaning "there is no value for this data point". This value is
determined by the EMPTY option in the \>HEAD block (Section 8.0). If the
option is not specified, its static default value is 1.00E+32.

In BNF notation, an ASCII data set is represented as:

\<ascii_data_set\> ::= "//" \<unsign_int\> { \<number\> }

EDI files are always ASCII files, made up of readable, printable
characters. However, a mechanism is provided for a parallel binary file
containing data values in binary form. The BINDATA option in the \>HEAD
block (Section 8.0) allows the EDI file to reference another file which
must contain only binary data.

If the BINDATA option is the null string (null is the static default),
then the EDI file must contain only ASCII data. If the BINDATA option is
not null, then it assumed that some or all data values will be read from
a parallel binary file. When reading an EDI file which references binary
data, the user will have to tell the reading program the name of the
binary file to be used. Sufficient information must be provided in the
tape header or through other means for the user to relate binary files
to EDI files.

The appropriate binary file will be opened and rewound at the time the
EDI file is opened. The first item in the binary file is a 16 character
file tag (written with a FORTRAN 16A image or equivalent) which
identifies the data set. This file tag must exactly agree with the
string in the BINDATA option in the \>HEAD block or a mismatch error
occurs.

Data sets will always be read sequentially from that current file
pointer position in the binary file. A data set consists of a count and
a set of data values. The count is a 16 bit two's-complement integer
(FORTRAN INTEGER\*16 or equivalent). It gives the number of values in
the data set, 0 to 32767. A count of zero represents an empty data set.
The data values which follow are in one of the three supported binary
formats. The number of values must be EXACTLY equal to the value of
count. Any or all of the data values may be represented with a special
value meaning "there is no value for this data point". This value is
determined by the EMPTY option in the \>HEAD block (Section 8.0). If the
option is not specified, its static default value is 1.00E+32 (be
careful to use a value which is exactly representable in the specified
format).

**Hint:** The use of binary data is discouraged except in situations
where the volume of data makes it impractical to use an ASCII
representation. In practice, time series data (\>TSERIES) blocks are the
only place where this might occur (see Section 10.2).

In BNF notation, binary data are represented (in the EDI file) as:

\<bin_data_set\> ::= "/I/" \| "/R/" \| "/D/"

A measurement ID set is a special case of a data set. It cannot be a
binary data set. Its elements must be unsigned integers or unsigned
reals. In BNF notation it may be represented as:

\<meas_ID_set\> ::= "//" \<unsign_int\> { \<unsign_int\> \|
\<unsign_real\> }

In summary, the BNF notation for a data set is represented as:

\<data_set\> ::= \<ascii_data_set\> \| \<bin_data_set\> \|
\<meas_ID_set\>

ASCII should be considered the primary method for data representation in
an EDI file. A provision for handling binary data has been included to
accommodate very large data sets such as time series where the more
compact representation of data is absolutely necessary.

###  6.24 Option Lists

Option lists may be a part of many of the data blocks defined below. An
option list is simply a sequence of option names followed by a
corresponding option argument. The option name is an abbreviated
mnemonic keyword such as NCHAN for number of channels or BW for
bandwidth. The option argument may be a string, a number, a date, or a
lat/long. All of these were syntactically defined in Section 6.22. The
option name and option argument are always separated by an equals sign.
In BNF notation:

\<option_name\> ::= \<letter\> { \<letter\> \| \<digit\> }

\<option arg\> ::= \<string\> \| \<number\> \| \<date\> \| \<real\> \|
\<lat_long\>

\<option\> ::= \<option name\> "=" \<option arg\>

\<option list\> ::= { \<option\> }

A list of allowed options is given for each keyword in sections 8-20.
Included in the list are any restrictions and defaults for each option.
Default values for options are applied if an option is omitted from the
option list. Options may be required, have static defaults, or have
dynamic defaults. Dynamic defaults depend upon previously set values.
The first block in a new section can define the dynamic defaults for
some options. Then, any data block within the section can use the
default value by not specifying that option or may specify a different
value by specifying the option. There are nine defined dynamic defaults:
HX, HY, HZ, EX, EY, RX, RY, NF, and NC.

###  6.25 Comments

Comments can be placed anywhere in an EDI file where a space could occur
except within a data set. A comment begins with the two character
sequence "\>!" . It is terminated by another exclamation point "!".
Between these may be any number of legal characters (Section 6.22)
except, of course, for "!". In non-standard annotated BNF notation:

\<comment\> ::= "\>!" {\<legal char\> } "!"\
(Where \<legal_char\> does not include "!" or "\>")

Characters within a comment have no syntactic meaning; they are used
simply for enhancing the readability of an EDI file. Comments may not
appear within data sets. They cannot be nested. The characters within
comments are read from logical records just as the other characters.

#  7.0 High Level Organization of Data Interchange Files

##  7.1 Overview

An EDI file is organized very much like the source file for a computer
program. Its basic element is a data block (analogous to a program
statement). Sometimes, contiguous data blocks are grouped into larger
units called data sections (analogous to subroutines). All data blocks
begin with a keyword. A keyword is the character "\>" followed by 1 to
16 letters. As in a programming language, the type of data block and its
semantics depend on what the keyword is. Special keywords, beginning
with a right arrow character and an equal character "\>=", indicate data
blocks which define the beginning of a data section (analogous to
SUBROUTINE statements). Following the keyword may be an option list
(section 6.24), and following this may be a data set (section 6.23).
Whether the option list and/or data set is required depends on the type
of the data block. In BNF notation:

\<keyword\> ::= "\>" \<letter\> { \<letter\> \| \<digit\> }

\<data_block\> ::= \<keyword\> \|

::= \<keyword\> \<option_list\> \|

::= \<keyword\> \<data_set\> \|

::= \<keyword\> \<option_list\> \<data_set\>

It should be noted that the "\>" character is also used to begin
comments. Other than keywords and comments, the "\>" character should
not appear in an EDI file (i.e., not in the \>INFO text or within
comments). This restriction enables rapid scanning of EDI files.

An EDI file consists basically of the following elements:

\(1\) A \>HEAD block

\(2\) An \>INFO block

\(3\) Info Text

\(4\) A Define Measurements Section

\(5\) One or More Data Sections of the following types

\(a\) Time Series Data

\(b\) Spectra Data

\(c\) MT Data

\(d\) EMAP Data

\(e\) Other Data

\(6\) An \>END block

Each of these elements is discussed in the sections which follow.

##  7.2 \>HEAD Block

All EDI files must begin with a \>HEAD block (analogous to a PROGRAM
statement). The \>HEAD block uses an option list (Section 6.24) to
define a number of conventions which apply to the entire file. It has no
data set.

\<head_block\> ::= "\>HEAD" \<option_list\>

##  7.3 \>INFO Block

Immediately after the \>HEAD block, is an \>INFO block. It also has an
option list but no data set. Following the \>INFO block is free-form
text. This is the repository for all important notes regarding the
acquisition and processing of the data within the file. The info text
continues until the next keyword is encountered. In BNF notation:

\<info_block\> ::= "\>INFO" \<option_list\>

\<info_text\> ::= { \<legal_char\> }\
( Note: legal character does not include "\>" )

##  7.4 \>=DEFINEMEAS Section

Following the \>INFO text, there must be a define measurements section
which defines all of the measurements which will be referenced within
the file. Each measurement is assigned a unique measurement ID by which
it may later be referenced. It is analogous to the DIMENSION statements
in a program. The section begins with a \>=DEFINEMEAS block. The option
list for this block defines the reference system to be used for sensor
locations and other parameters. The block has no data set.

The rest of the define measurements section consists of a series of
\>EMEAS and \>HMEAS data blocks, one for each electric or magnetic field
measurement. A measurement references both a channel and a run to
uniquely identify a particular set of data. The definition of a
measurement includes a complete description of the sensor location(s)
and configuration, sensor ID, filters, gain, acquisition channel, etc.
(See Channel, Run, and Measurement ID under Terms and Definitions).

Each \>EMEAS or \>HMEAS block uses an option list to specify the
location and orientation of the data sensor(s) as well as information
pertaining to the run.

\<emeas_block\> ::= "\>EMEAS" \<option_list\>

\<hmeas_hlock\> ::= "\>HMEAS" \<option_list\>

\<def_meas_section\> ::= "\>=DEFINEMEAS" \<option_list\>\
{ \<emeas_block\> \| \<hmeas_block\> }

##  7.5 Data Sections

Following the define measurement section may be one or more data
sections. Five types of data sections are presently defined: time series
data, spectra data, MT data, EMAP data, and other data. Data sections
may be in any order and there may be more than one of a given type.

Although data sections are completely independent of one another, it is
strongly recommended that the same set of frequencies (and their order)
be used for all data sections pertaining to the same data set. For
example, the frequencies for an \>=MTSECT data section should be exactly
the same as those for the corresponding \>=SPECTRASECT data section.

###  7.51 Time Series Data Sections

If time series data are included in the EDI file, it is in one or more
time series data sections. Each time series data section begins with a
\>=TSERIESSECT block. This block has an option list which defines the
number of data measurements and other parameters. It also has a data set
which contains an ordered list of the measurement ID's which define the
set of measurements for which data are presented.

The rest of the section consists of one or more \>TSERIES blocks. Each
block has an option list which completely describes the organization of
the time series data. This block has an option list which defines the
number of data measurements and other parameters. It also has a data set
which contains an ordered list of the measurement ID's which define the
set of measurements for which data are presented. Following this is a
data set which contains the actual time series data. In BNF notation:

\<tseriessect_block\> ::= "\>=TSERIESSECT" \<option_list\>
\<mead_ID_set\>

\<tseries_block\> ::= "\>TSERIES" \<option_list\> \<data_set\>

\<tseries_section\> ::= \<tseriessect_block\> { \<tseries_block\> }

Because acquisition systems vary so much, it is very important that the
acquisition hardware and system response be adequately documented or
referenced in the \>INFO section.

###  7.52 Spectra Data Sections

If power spectra data are included in the EDI file, it is in one or more
spectra data sections. Each spectra data section begins with a
\>=SPECTRASECT block. This block has an option list which defines the
number of data measurements and other parameters. It also has a data set
which contains an ordered list of the measurement ID's which define the
set of measurements for which data are presented.

The rest of the section consists of one or more \>SPECTRA blocks, one
for each frequency. Each spec data block has an option list which
defines the frequency, bandwidth, and other parameters which
characterize the possible auto and cross power spectra for the entire
set of measurements.

In BNF notation:.

\<spectrasect_block\> ::= "\>=SPECTRASECT" \<option_list\>
\<meas_ID_set\>

\<spectra_block\> ::= "\>SPECTRA" \<option_list\> ";" \<data_set\>

\<spectra_section\> ::= \<spectrasect_block\> { \<spectra_block\> }

###  7.53 MT Data Sections

It will often be most convenient to use a separate EDI file for each MT
sounding. However, one or more MT soundings may be included in an EDI
file, each in its own MT data section. Each of these MT data sections
begin with an \>=MTSECT data block. The option list for this block
contains default measurement ID's for up to five MT components and two
references. It has no data set.

If data for multiple rotations are to be presented, a separate \>=MTSECT
data section should be used for each rotation.

Following the \>=MTSECT block must be a \>FREQ data block. The data set
with this block defines the frequency set for the sounding. Following
the \>FREQ block are data blocks for the sounding.

First are the impedance data blocks. If the impedances are not in the
measurement directions, the first impedance block must be \>ZROT. For
MT, up to four Z components may be included: ZXX, ZXY, ZYX, and ZYY. For
each component, there may be up to 6 data blocks. No provision has been
made to include separate data sets for impedance polar diagrams because
they can be calculated so easily from the four Z components.

Next are the apparent resistivity data blocks. If the impedances are not
in the measurement directions, the first impedance block must be
\>RHOROT. For MT, up to four apparent resistivities may be included:
RHOXX, RHOXY, RHOYX, and RHOYY. For each of these there are
corresponding PHS and up to 6 other data blocks.

Next are the continuous 1-D inverse data blocks. There may be up to four
inversions corresponding to the four apparent resistivities above. For
each of these there may be RES1D and DEPTH1D data blocks.

Finally, are all of the other data blocks for the MT sounding. These
include coherencies, predicted coherencies, signal amplitudes,
signal-to-noise, up to 8 tipper parameters, strikes, skews,
ellipticities, and ".EXP" data blocks.

All of these data blocks are discussed in detail in the sections below.
In BNF form, an MT data section can be represented as:

\<mtsect_block\> ::= "\>=MTSECT" \<option_list\>

\<mt_data_block\> ::= \<keyword\> \<option_list\> \<data_set\>

\<mt_section\> ::= \<mtsect_block\> { \<mt_data_block\> }

###  7.54 EMAP Data Sections

An EMAP data section contains an EMAP profile or a section of an EMAP
profile. Each of these EMAP data sections begin with an \>=EMAPSECT
block. This block has an option list which contains the default
measurement ID's for the magnetic and reference components. The data set
for this block contains an ordered list of measurement ID's which define
the EMAP array.

Following the \>=EMAPSECT block must be a \>FREQ data block which
defines the frequency set for the profile. Following the \>FREQ block
are data blocks for the profile.

First are the impedance data blocks. Impedances for an EMAP profile must
be in the measurement directions. Therefore, an EMAP section can not
have a \>ZROT data block. For an EMAP profile, there are up to two Z
components: ZXX and ZXY. There may also be spatially filtered
components: FZXX and FZXY. For each component, there may be up to 6 data
blocks.

Next are the apparent resistivity data blocks. Because the apparent
resistivities for an EMAP profile correspond to the measurement
directions, the default for the ROT option, ROT=NONE should be used. For
an EMAP profile, up to four apparent resistivities may be included:
RHOXX, RHOXY FRHOXX, and FRHOXY . For each of these there are
corresponding PHS and up to 6 other data blocks.

Next are the continuous 1-D inverse data blocks. There may be up to four
inversions corresponding to the four apparent resistivities above. For
each of these there may be RES1D and DEPTH1D data blocks.

Finally, are all of the other data blocks for the EMAP profile. These
include coherencies, predicted coherencies, signal amplitudes,
signal-to-noise, spatial filter information, and ".EXP" data blocks.

All of these data blocks are discussed in detail in the sections below.
In BNF form, an MT data section can be represented as:

\<emapsect_block\> ::= "\>=EMAPSECT" \<option_list\> \<meas_ID_set\>

\<emap_data_block\> ::= \<keyword\> \<option_list\> \<data_set\>

\<emap_section\> ::= \<emapsect_block\> { \<emap_data_block\> }

###  7.55 Other Data Sections

For defined techniques such as MT and EMAP, data blocks have been
ordered and restricted to simplify processing and assure consistent and
reasonable data. However, the standard also includes a provision for the
unrestricted inclusion data blocks for non-standard applications.

All of these data blocks are discussed in detail in the sections below.
In BNF form, an MT data section can be represented as:

\<othersect_block\> ::= "\>=OTHERSECT" \<option_list\> \<meas_ID_set\>

\<data_block\> ::= \<keyword\> \<option_list\> \<data_set\>

\<other_section\> ::= \<othersect_block\> { \<data_block\> }

##  7.6 \>END Block

Finally, the EDI file must conclude with an \>END block. It has no
option list and no parameters. In BNF notation, it is represented as:

\<end_block\> ::= "\>END"

##  7.7 \>BNF Representation of an EDI File

Using the non-terminals defined in Sections 7.1-7.6, we can represent
the syntax of an EDI file as follows:

\<edi_file\> ::= \<head_block\>\
\<info_block\>\
\<info_text\>\
\<def_meas_section\>\
{ \<tseries_section\> \| spectra_section\> \|\
\<mt_section\> \| \<emap_section\> \| \<other_section\> }\
\<end_block\>

#  8.0 Head, Info, Frequency, Zrot, Rhorot, & End Blocks

##  8.1 \>HEAD

**Description:** The head block contains a series of options which (1)
identify the data set, (2) describe when, where, and by whom it was
acquired, and (3) describe when, how and by whom it was written.

**Example:**

\>HEAD

DATAID=DEMO88

ACQBY=\"ACME MT\"

FILEBY=\"ACME MT\"

ACQDATE=04/30/88

FILEDATE=06/06/88

PROSPECT=DEMO88

LOC=\"DEMO PROSPECT\"

LAT=+30:20:00

LONG=-122:20:00

ELEV=200

STDVERS=\"SEG 1.0\"

PROGVERS=1.0

PROGDATE=08/07/89

MAXSECT=999

EMPTY=1.0E+32

**Restrictions:** Exactly one \>HEAD block is allowed per file. It must
be the first block in the file.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

DATAID Identifier for data set String Required

ACQBY Name of contractor or other party String Required

FILEBY Name of contractor or other party String Required

ACQDATE Date of (start of) data acquisition Date Required

ENDDATE Date of end of data acquisition Date or " " " "

FILEDATE Date EDI file was written Date Required

COUNTRY Name of country of acq String or " " " "

STATE State(s) / Province(s) of acq String or " " " "

COUNTY County(s) of acq. String or " " " "

PROSPECT Name of associated prospect(s) String or " " " "

LOC Description of location of Acq String or " " " "

LAT Avg. (approx) latitude of Acq Latitude or " " " "

LONG Avg. (approx) longitude of Acq Longitude or " " " "

ELEV Avg (approx) elevation of Acq Number or " " " "

UNITS Units for elevation "M" or "FT" "M"

STDVERS Version of EDI Format for this file String Required

PROGVERS Version ID for prog writing file String Required

PROGDATE Last Revision of prog writing file String Required

MAXSECT Maximum data sections in EDI file Integer\> =1 "16"

BINDATA If not " ", tag for binary data file String or " " " "

EMPTY Value which represents "no data" Number "1.0E32"

**Data Set:** None

**Notes:** 1. The LAT and LONG options are required for measured data,
but not for model data.

2\. The BINDATA option is " " if there is no parallel binary data file.
If one or more of the data blocks in the file refer to binary data, this
is a tag which must appear at the very beginning of the binary data
file. This assures proper matching of EDI and binary files (Section
6.23).

3\. The EMPTY option defines a special value which represents an empty
data value. When this value is encountered in any data record in the
file, it is interpreted as "there is no value for this data point".
Because of the limits in converting between real numbers and their
textual representations, care should be taken in selecting this value.

**Hints:** 1. Remember that the maximum length for any option argument
is 16 characters. If it is a string option and the argument contains
blanks, you must enclose the argument in double quotes "\"" (total
length of quoted string is 18 chars). Do not quote numbers, integers,
dates, or latitude/longitudes.

2\. Remember that the format for dates must be mm/dd/yy and the format
for latitudes and longitudes is ddd:mm:ss.s. West longitudes are
negative.

3\. Set the DATAID to the name of the survey. Usually the ACQBY and
FILEBY will be filled in with the name of the contractor. ACQDATE must
be filled in with the date the survey began and FILEDATE must give the
date the EDI file was written. All of these fields are required.

4\. The options ENDDATE, COUNTRY, STATE, COUNTY, PROSPECT, LOC, LAT,
LONG, AND ELEV are not required. It is recommended, however, that these
be filled in for documentation purposes. If LAT, LONG, and ELEV are set,
use the same location as the REFLAT, REFLONG, and REFELEV options in the
\>=DEFINEMEAS block (see Section 9.1).

5\. If your distance units for this survey are feet, then you must
specify this using the UNITS option. Otherwise, meters will be assumed.

6\. The options STDVERS must be set to "1.0" (this version of the
standard). The PROGVERS and PROGDATE options must be filled in with
sufficient information that whoever was listed in the FILEBY option
could identify (and hopefully find) the program used to write the EDI
file.

7\. If you have more than 16 data sections (generally a section is the
spectra or plots for one site) in this file, then set MAXSECT to an
appropriately big value.

8\. You do not need to specify the BINDATA option unless there is binary
data associated with this file. You do not need to specify the EMPTY
option unless you are using a value other than 1.0E32 to represent
missing data values. USE AN EXPLICIT EMPTY VALUE to represent missing or
null data (1.0E32 is recommended). Do not use zero for this purpose.

##  8.2 \>INFO

**Description:** The \>INFO block indicates the beginning of free-form
text. This text section is to contain all important notes concerning
data acquisition and processing. Any non-standard practices used must be
documented here. The text may not include any legal characters except
for the character "\>".

**Example:**

\>INFO MAXINFO=2000

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

Run Information

Calibration Files

Project: DEMO PHASE 1 Digitizer: D#209-10Mar88-10

Client: BIGOIL PETROLEUM SP\--Stn01: B#219-14Mar88-05

Run: DEMO88-101/102 SP\--Stn02: B#336-14Mar88-05

Sens-Ch01: C#238-11Mar88-01

Operator: SMITH Sens-Ch02: C#239-11Mar88-01

Date: 30 Apr 1988 Sens-Ch03: L#333-12Mar88-01

Time: 15:48:30 Sens-Ch06: C#431-11Mar88-01

Sens-Ch07: C#309-11Mar88-01

Program Version: ACQSYSTEM Sens-Ch08: L#334-12Mar88-01

Latest Revision: 01 Feb 1988

MT Ref Field: 4 = Rem H Ref

XPR Weighting: RHO VAR STN

XPR Recording Hi Passes: 2

XPR Recording Lo Stacks: 1500

Notch Filters: 60,180,300 Hz

Digitizer: D209

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

Operator Log for DEMO88-101/102

DEMO88-101/102

Start: 15:58:30 30 Apr 1988

End: 06:05:26 1 May 1988

Cultural Factors:

People near both sites during daylight hours. Electrical lines 1.2 km to
the south.

Weather Conditions:

Dry and very hot. Light breeze at times. Some distant lightning late in
evening.

Other Factors:

Low signal levels overnight.

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

Summary of Stacks & Quality

Freq Unedited Edited Unedited Edited

Num Stacks Stacks Quality Quality

1 2141 1790 .703 .712

2 2141 1662 .746 .773

3 2144 1728 .684 .724

4 2144 1664 .645 .654

5 36797 17901 .612 .635

6 36797 17901 .596 .609

7 18380 9571 .424 .394

8 18380 8947 .338 .302

9 9171 5071 .202 .162

10 9171 4239 .121 .101

11 4467 2409 .049 .037

12 4593 2553 .027 .024

13 2248 1456 .019 .015

14 2188 276 .020 .017

15 1018 126 .016 .023

16 1084 982 .019 .019

17 529 255 .024 .035

18 555 495 .024 .024

19 486 204 .015 .020

20 594 132 .017 .035

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

**Restrictions:** Exactly one \>INFO block is allowed per file. It must
be the second block in the file, immediately after the \>HEAD block.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

MAXINFO Maximum number of text lines in Integer \>=1 "256"\
info text (may be less).

**Data Set:** None

**Notes:** None

**Hints:** 1. Be generous with the relevant material you include in the
INFO text. Put yourself in the shoes of an interpreter using this data
10 years from now.

2\. Design your acquisition and processing so that they automatically
generate machine readable layout information, operator logs, and data
stacking & processing logs. It is then easy to paste these together to
create a very complete INFO text.

3\. Be careful not to include the "\>" character anywhere in the INFO
text. This is the character used to terminate it. Any text which was
typed in such as an operator log should always be scanned for the
inclusion of this character.

4\. You only need to set the MAXINFO option if you are including more
than 256 lines of text. Although the standard allows lines (records) up
to 128 characters in length, limit your lines to 80 characters so that
they can be viewed comfortable on any terminal or PC.

##  8.3 \>FREQ

**Description:** Data block containing a set of frequencies in Hz. It
defines the frequency set for succeeding data within that data section
which are functions of frequency.

**Example:**

\>FREQ //20

1.20000000E+01 9.00000000E+00 6.00000000E+00 4.50000000E+00
3.00000000E+00

2.25000000E+00 1.50000000E+00 1.12500000E+00 7.50000000E-01
5.62500000E-01

3.75000000E-01 2.81250000E-01 1.87500000E-01 1.40625000E-01
9.37500000E-02

7.03125000E-02 4.68750000E-02 3.51562500E-02 2.34375000E-02
1.75781250E-02

**Restrictions:** Exactly one \>FREQ block is required to immediately
follow \>=MTSECT or \>=EMAPSECT blocks. One or more may appear anywhere
in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

ORDER Ordering of frequencies "INC" or "DEC" "DEC"

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Must contain NFREQ values in strictly increasing or
decreasing order as specified by the ORDER option. The values must be
within the legal range for reals and \>0. Empty data values and empty
data sets (Section 6.23) are not allowed.

**Notes:** 1. The dynamic default for NF was set by the NFREQ option in
the section head block.

2\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. Because of the limits
in formatting real numbers, care should be exercised in writing and
testing checksums.

**Hints:** 1. Generally the NFREQ option will be provided by the
\>=MTSECT or \>=EMAPSECT block through the dynamic default mechanism.
The number given in the NFREQ option must be the exactly same number
that follows the two slashes "//" and the number of data values. Always
begin the actual data values on a new line.

2\. The frequencies must be monotonic in either increasing or decreasing
order. Therefore, if the data was acquired in overlapping bands, the
contractor must merge the bands such that the frequencies are in order.
If the order is increasing then use the \"ORDER=INC\" option. Otherwise,
decreasing order is assumed.

3\. The \>FREQ block appears only in MT sections (\>=MTSECT) and other
sections containing computed parameters. It must be the first block in
the section. It is not used for spectra sections (\>=SPECTRASECT) where
each \>SPECTRA block has its own frequency.

4\. Note that the same number of values and order is assumed for all
other records in the section (unless the dynamic default is overridden).
If you have to sort the frequencies, you must sort all of the other data
records in the section the same way.

5\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

##  8.4 \>ZROT

**Description:** Data block containing a set of rotation angles used for
impedances.

**Example:**

\>ZROT // 20

5.5246933E+01 3.1937851E+01 3.3514709E+01 2.0876354E+01 2.5652016E+01

2.5561487E+01 2.8420677E+01 2.7789608E+01 2.7317364E+01 3.2120583E+01

4.1798073E+01 2.8956604E+01 1.2983720E+01 4.0194614E+01 1.3554901E+01

2.6992781E+01 1.1652201E+01 2.3906601E+01 2.8832569E+01 -2.7098677E+01

**Restrictions:** One \>ZROT block may optionally appear in an \>=MTSECT
data section. If present, the \>ZROT block must immediately follow the
\>FREQ block. It may not appear in an \>=EMAPSECT data section. One or
more may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the rotation angles for the impedances at the
corresponding frequencies. The values must be within the legal range for
angles (Section 5.1). The data set may not contain empty values (Section
6.23). It may not be an empty data set and may not contain binary data
(Section 6.23).

**Notes:** 1. The dynamic default for NF was set by the NFREQ option in
the first block of the section.

2\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. Because of the limits
in formatting real numbers, care should be exercised in writing and
testing checksums.

**Hints:** 1. The number that follows the two slashes "//" and the
number (and order) of data values should be the same as that specified
by the NFREQS option in the first data block (\>FREQ) in the section. If
this is true, it is not necessary to re-specify the NFREQ option here.
Always begin the actual data values on a new line.

2\. The \>ZROT block appears only in MT sections (\>=MTSECT) and other
sections containing computed parameters. It is only needed if you are
going to include any impedance (Z) blocks in the section and the ROT
option for those blocks is set to ROT=ZROT. It must precede any
impedance blocks.

3\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

##  8.5 \>RHOROT

**Description:** Data block containing a set of rotation angles used for
apparent resistivities.

**Example:**

\>RHOROT // 20

5.5246933E+01 3.1937851E+01 3.3514709E+01 2.0876354E+01 2.5652016E+01

2.5561487E+01 2.8420677E+01 2.7789608E+01 2.7317364E+01 3.2120583E+01

4.1798073E+01 2.8956604E+01 1.2983720E+01 4.0194614E+01 1.3554901E+01

2.6992781E+01 1.1652201E+01 2.3906601E+01 2.8832569E+01 -2.7098677E+01

**Restrictions:** One \>RHOROT block may optionally appear in an
\>=MTSECT data section. If present, the \>RHOROT block must immediately
follow the \>FREQ block and any impedance blocks. It may not appear in
an \>=EMAPSECT data section. One or more may appear anywhere in
\>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the rotation angles for the apparent resistivities at
the corresponding frequencies. The values must be within the legal range
for angles (Section 5.1). The data set may not contain empty values
(Section 6.23). It may not be an empty data set and may not contain
binary data (Section 6.23).

Notes: 1. The dynamic default for NF was set by the NFREQ option in the
first block of the section.

2\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. Because of the limits
in formatting real numbers, care should be exercised in writing and
testing checksums.

**Hints:** 1. The number that follows the two slashes "//" and the
number (and order) of data values should be the same as that specified
by the NFREQS option in the first data block (\>FREQ) in the section. If
this is true, it is not necessary to re-specify the NFREQ option here.
Always begin the actual data values on a new line.

2\. The \>RHOROT block appears only in MT sections (\>=MTSECT) and other
sections containing computed parameters. It is only needed if you are
going to include any rho, phase, or res1d blocks in the section and the
ROT option for those blocks is set to ROT=RHOROT. It must precede any of
these blocks.

3\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

##  8.6 \>END

**Description:** Denotes the end of an EDI File.

**Example:**

\>END

**Restrictions:** Exactly one \>END block is allowed per file. It must
be the last block in the file.

**Options:** None

**Data Set:** None

##  8.7 \>! Comment !

**Description:** Begins a comment.

**Example:**

\>! This is a comment which can be inserted (almost) anywhere in an EDI
file !

**Restrictions:** Comments may appear anywhere in an EDI file where a
space may appear except within data sets. Any legal characters may
appear within a comment except for "!" and "\>".

**Notes:** \>! is only a pseudo keyword which causes all following
characters to be syntactically ignored until another exclamation
character ! is encountered.

**Hints:** 1. The one place where comments can not appear is inside a
data set. After an EDI reading program finds "//" followed by a number,
it expects to be able to read that many values beginning with the next
record. For efficiency a Fortran unformatted read is often used here and
it does not understand comments.

2\. Comments should begin and end on the same line. Although not
required, it is better to put comments on their own separate line if
possible.

3\. Be sure that the characters "!" and "\>" do not appear within the
comment.

4\. Note that blank lines can appear anywhere in an EDI file except for
within a data set (see hint 1 above). They can be used to greatly
enhance the readability of an EDI file.

#  9.0 Measurement Definition Blocks

##  9.1 \>=DEFINEMEAS

**Description:** Begins a Measurement Definition data section. Defines
locations of sensors and parameters pertaining to runs for each
measurement.

**Example Measurement Definition Section:**

\>=DEFINEMEAS\
MAXRUN = 999\
MAXMEAS = 1000\
REFTYPE = \"UTM 6\"\
REFLAT = 30:15:22.2\
REFLONG = -98:16:20.0

\>! Measurements for Site 11. Located at reference. 100M lines layed out
at 45 deg !\
\>HMEAS ID=111.001 CHTYPE=HX X=0.0 Y=0.0 AZM=45\
\>HMEAS ID=112.001 CHTYPE=HY X=0.0 Y=0.0 AZM=135\
\>HMEAS ID=113.001 CHTYPE=HZ X=0.0 Y=0.0 AZM=0\
\>EMEAS ID=114.001 CHTYPE=EX X=-70.7 Y=-70.7 X2=70.7 Y2=70.7\
\>EMEAS ID=115.001 CHTYPE=EY X=70.7 Y=-70.7 X2=-70.7 Y2=70.7

\>! Measurements for Site 12. Located at 1 km north and 1 km east of
reference. 100M lines layed out at 30 deg !\
\>HMEAS ID=121.001 CHTYPE=HX X=1000.0 Y=1000.0 AZM=30\
\>HMEAS ID=122.001 CHTYPE=HY X=1000.0 Y=1000.0 AZM=120\
\>HMEAS ID=123.001 CHTYPE=HZ X=1000.0 Y=1000.0 AZM=0\
\>EMEAS ID=124.001 CHTYPE=EX X=913.4 Y=950.0 X2=1086.6 Y2=1050.0\
\>EMEAS ID=125.001 CHTYPE=EY X=1050.0 Y=913.4 X2=950 Y2=1086.6

**Restrictions:** Exactly one instance of a \>DEFINEMEAS data block can
appear in an EDI file. It must immediately follow the \>HEAD block,
\>INFO block, and info text.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

MAXCHAN Maximum number of channels Integer \>=1 "16"

MAXRUN Maximum number of runs Integer \>=1 "0"

MAXMEAS Maximum number of measurements Integer \>=1 "64"

UNITS Units for sensor offsets from reference "M" or "FT" "M"

REFTYPE Type of offset from reference String "CART"

REFLOC Description of location of reference String or " " " "

REFLAT Latitude of reference Latitude or " " " "

REFLONG Longitude of reference Longitude or " " " "

REFELEV Elevation of reference Number or " " " "

**Data Set:** None

**Notes:** 1. MAXCHAN is the maximum channel number used in the EDI
file. MAXRUN is the maximum run number used in the EDI file. Measurement
IDs incorporate both channel number and run number. The integer part is
the channel number. There may be a fractional part which gives the run
number. The run number for the first run is always 0. Thus, there is no
fractional part in the measurement ID's for the first (and often only)
run in the file. The number of digits in the fractional part is 2, 3, or
4, depending on the value of the MAXRUN option in the \>=DEFINEMEAS data
block. If the value is 0 (default), then all measurement IDs are simply
the channel number. If the MAXRUN \<100, then all measurement IDs are
chan num+(run num/100). If MAXRUN is \>=100 and \<1000 then all
measurement IDs are chan num+(run num/1000). Finally, if MAXRUN is
\>=1000, then measurement IDs are chan num+(run num/10,000).

2\. The REFLAT, REFLONG, and REFELEV options are required for measured
data, but not for model data.

3\. All sensor locations within the section are defined relative to an
arbitrary reference location. The reference type describes the Cartesian
projection in which X, Y, and Z offsets relative to the reference define
a sensor location. The offsets are in meters unless the UNITS=FT option
is specified. Positive X, Y, and Z offsets correspond to true north,
east, and up from the reference, respectively. Because such a coordinate
system begins to deviate after 7-10 minutes of longitude, other
reference types may be added to the standard in the future to handle
more sophisticated specification of sensor locations.

**Hints:** 1. The measurement definition section is always required
whether an EDI file contains computed parameters such as an MT section
(\>=MTSECT) or spectra (\>=SPECTRASECT) or both.

2\. The location of every E and H sensor used to acquire the data in the
EDI file is defined in terms of offsets from a single reference
location. Positive X is north and positive Y is east.

3\. The REFLAT and REFLONG options specify the reference location. If
the data for a survey is spread across multiple EDI files, it is
recommended, but not required that all use the same reference location.
The reference location should generally be near the center of the
survey. The REFELEV and REFLOC may optionally be provided. If REFELEV is
not specified, it is assumed to be zero.

4\. Each measurement in a survey must have a measurement id which is
unique across the entire survey, even if it spans multiple EDI files.
The following convention is suggested for generating unique measurement
id's.\
\
measid = 10 \* site number + channel +
$\frac{\text{run number}}{\text{1000}}$\
\
where channel = 1 for Hx\
2 for Hy\
3 for Hz\
4 for Ex\
5 for Ey\
6 for short remote Rx (not part of another site)\
7 for short remote Ry (not part of another site)

5\. A run number which is unique across the survey, even if it spans
multiple EDI files, is assigned to each acquisition run. Sometimes this
is referred to as a "setup". An acquisition crew might make 1 or 2 runs
per day, each consisting of one or more sites acquired simultaneously.
One simple way to assign run numbers is sequentially, beginning with run
1 at the beginning of the survey.

6\. The MAXCHAN option needs to be specified only if more than 16
channels are acquired simultaneously. The MAXRUN option should always be
set to 999 (this is necessary in order to use the suggested measurement
id naming in hint 3 above). The MAXMEAS option should be set to any
large value greater than 10 times the maximum site number. The UNITS
option should be set to UNITS=FT if feet are to be used to specify the
measurement locations within the section. Otherwise, meters are assumed.

7\. The REFTYPE option is used to describe the coordinate system in
which the offsets were computed. The recommended procedure is to use the
appropriate Universal Transverse Mercator (UTM) projection. Determine
the UTM zone in which the reference location resides and compute its UTM
coordinates using the projection for that zone. Use this same UTM
projection for computing the UTM coordinates of each site or sensor.
Subtract the reference coordinates to get the locations in terms of
offsets from the reference.

##  9.2 \>EMEAS

**Description:** Defines the electrode locations and run parameters for
an electric field measurement.

**Example:**

\>! E Measurements for Site 11. Located at reference. 100M lines layed
out at 45 deg !\
\>EMEAS ID=114.001 CHTYPE=EX X=-70.7 Y=-70.7 X2=70.7 Y2=70.7\
\>EMEAS ID=115.001 CHTYPE=EY X=70.7 Y=-70.7 X2=-70.7 Y2=70.7

\>! E Measurements for Site 12. Located at 1 km north and 1 km east of
reference. 100M lines layed out at 30 deg !\
\>EMEAS ID=124.001 CHTYPE=EX X=913.4 Y=950.0 X2=1086.6 Y2=1050.0\
\>EMEAS ID=125.001 CHTYPE=EY X=1050.0 Y=913.4 X2=950 Y2=1086.6

**Restrictions:** Zero or more \>EMEAS blocks can appear within the
Define measurements section. One block must be included for each
electrical field measurement which is used in the EDI file. Note that
multiple runs using the same channel are considered to be separate
measurements, each requiring an \>EMEAS block.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

ID Measurement ID Number \>=1 Required

CHTYPE Type of E measurement "EX" or "EY" Required

X X offset from ref for first electrode Number Required

Y Y offset from ref for first electrode Number Required

Z Z offset from ref for first electrode Number or " " " "

X2 X offset from ref for 2nd electrode Number Required

Y2 Y offset from ref for 2nd electrode Number Required

Z2 Z offset from ref for 2nd electrode Number or " " " "

ACQCHAN Description of acq chan for run String or " " " "

FILTER Description of filter(s) for run String or " " " "

GAIN Gain used for run Number \>0 or " " " "

MEASDATE Date of run Date or " " " "

**Data Set:** None

**Notes:** 1. The type is designated as EX or EY as appropriate.

2\. Measurement IDs incorporate both channel number and run number. The
integer part is the channel number. There may be a fractional part which
gives the run number. The run number for the first run is always 0.
Thus, there is no fractional part in the measurement ID's for the first
(and often only) run in the file. The number of digits in the fractional
part is 2, 3, or 4, depending on the value of the MAXRUN option in the
\>=DEFINEMEAS data block. If the value is 0 (default), then all
measurement IDs are simply the channel number. If the MAXRUN \<100, then
all measurement IDs are chan num+(run num/100). If MAXRUN is \>=100 and
\<1000 then all measurement IDs are chan num+(run num/1000). Finally, if
MAXRUN is \>=1000, then measurement IDs are chan num+(run num/10,000).

3\. For MT soundings EX usually designates the dipoles most nearly
oriented in the north-south direction and EY designates the
corresponding orthogonal dipoles. For measurements of type EX, the first
electrode is the southern-most of the pair. For measurements of type EY,
the first electrode is the western-most of the pair. For EMAP lines,
dipoles along the line are generally designated as EX, and any
perpendicular dipoles are designated EY. Along the line, the first
electrode should be defined consistently such that the first electrode
of each dipole is coincident with the second electrode of the previous
one.

4\. All electrode locations are relative to the reference location
defined in the \>=DEFINEMEAS block. Currently the only reference type
allowed is Cartesian in which X, Y, and Z offsets relative to the
reference define an electrode location. The offsets are in meters unless
the UNITS=FT option is specified in the \>=DEFINEMEAS block. Positive X,
Y, and Z offsets correspond to true north, east, and up from the
reference, respectively. Because such a coordinate system begins to
deviate after 7-10 minutes of longitude, other reference types may be
added to the standard in the future to handle more sophisticated
specification of sensor locations.

**Hints:** 1. Be sure to carefully read all of the hints for
\>=DEFINEMEAS above.

2\. The ID option must specify a measurement id which is unique across
the survey even if it spans multiple EDIFILES. The following is
suggested for generating unique E measurement id's.\
\
measid = 10 \* site number + channel +
$\frac{\text{run number}}{\text{1000}}$\
\
where channel = 4 for Ex\
5 for Ey

3\. The CHTYPE option must be set to either EX or EY.

4\. The coordinate of the first electrode for the E measurement is
(X,Y). The coordinate for the second electrode is (X2,Y2). These options
must be filled in with the offsets of the electrodes relative to the
reference for the entire survey. If you are doing simple MT where
electrode geometry is not critical (as it is in EMAP), it is usually
sufficient to generate these from the site offset, the line length, and
the line azimuth. First, determine the site offset as explained in hint
7 for \>=DEFINEMEAS above. Then compute the sensor offsets based on the
site offset. For example, assuming an X electrode configuration centered
at the site offset:\
\
X = X- E-length \* cos (E-angle)\
Y = Y- E-length \* sin (E-angle)\
X2 = X+ E-length \* cos (E-angle)\
X2 = Y+ E-length \* sin (E-angle)

5\. The Z and Z2 options do not need to be specified unless topography
is being taken into account.

6\. The options ACQCHAN, FILTER, GAIN, and MEASDATE may be filled in for
documentation purposes, but are optional.

##  9.3 \>HMEAS

**Description:** Defines the sensor location and orientation, and run
parameters for a magnetic field measurement.

**Example:**

\>! H Measurements for Site 11. Located at reference. Layed out at 45
deg !\
\>HMEAS ID=111.001 CHTYPE=HX X=0.0 Y=0.0 AZM=45\
\>HMEAS ID=112.001 CHTYPE=HY X=0.0 Y=0.0 AZM=135\
\>HMEAS ID=113.001 CHTYPE=HZ X=0.0 Y=0.0 AZM=0

\>! H Measurements for Site 12. Located at 1 km north and 1 km east of
reference. Layed out at 30 deg !\
\>HMEAS ID=121.001 CHTYPE=HX X=1000.0 Y=1000.0 AZM=30\
\>HMEAS ID=122.001 CHTYPE=HY X=1000.0 Y=1000.0 AZM=120\
\>HMEAS ID=123.001 CHTYPE=HZ X=1000.0 Y=1000.0 AZM=0

**Restrictions:** Zero or more \>HMEAS blocks can appear within the
Define measurements section. One block must be included for each
magnetic field measurement which is used in the EDI file. Note that
multiple runs using the same channel are considered to be separate
measurements, each requiring an \>HMEAS block.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

ID Measurement ID Number \>=1 Required

CHTYPE Type of H measurement "HX","HY", or "HZ" Required

X X offset from ref for sensor Number Required

Y Y offset from ref for sensor Number Required

Z Z offset from ref for sensor Number Required

AZM Azimuth angle for sensor Number Required

DIP Dip angle for sensor Number "0"

ACQCHAN Description of acq channel for run String or " " " "

FILTER Description of filter(s) for run String or " " " "

SENSOR Description of sensor for run String or " " " "

GAIN Gain used for run Number \>0 or " " " "

MEASDATE Date of run Date or " " " "

**Data Set:** None

**Notes:** 1. If the measurement is a vertical magnetic field
measurement, its type should be HZ. Otherwise, it should be HX or HY as
appropriate.

2\. For MT soundings, HX usually designates the measurements most nearly
oriented in the north-south direction, and HY designates the
corresponding orthogonal measurements. For EMAP surveys, magnetic field
measurements parallel to the line are generally designated as HX, and
measurements perpendicular to the line are designated HY.

3\. Measurement IDs incorporate both channel number and run number. The
integer part is the channel number. There may be a fractional part which
gives the run number. The run number for the first run is always 0.
Thus, there is no fractional part in the measurement ID's for the first
(and often only) run in the file. The number of digits in the fractional
part is 2, 3, or 4, depending on the value of the MAXRUN option in the
\>=DEFINEMEAS data block. If the value is 0 (default), then all
measurement IDs are simply the channel number. If the MAXRUN \<100, then
all measurement IDs are chan num+(run num/100). If MAXRUN is \>=100 and
\<1000 then all measurement IDs are chan num+(run num/1000). Finally, if
MAXRUN is \>=1000, then measurement IDs are chan num+(run num/10,000).

4\. All sensor locations are relative to the reference location defined
in the \>=DEFINEMEAS block. Currently the only reference type allowed is
Cartesian in which X, Y, and Z offsets relative to the reference define
an electrode location. The offsets are in meters unless the UNITS=FT
option is specified in the \>=DEFINEMEAS block. Positive X, Y, and Z
offsets correspond to true north, east, and up from the reference,
respectively. Because such a coordinate system begins to deviate after
7-10 minutes of longitude, other reference types may be added to the
standard in the future to handle more sophisticated specification of
sensor locations.

5\. Azimuth angles are measured on a level plane, plus or minus 180
degrees relative to true north with positive angles being clockwise. Dip
angles are plus or minus 90 degrees relative to that level plane. Loop
type sensors should be treated like the equivalent coil; that is, a coil
which is normal to, and in the center of the plane defined by the loop
sensor.

**Hints:** 1. Be sure to carefully read all of the hints for
\>=DEFINEMEAS above.

2\. The ID option must specify a measurement id which is unique across
the survey even if it spans multiple EDIFILES. The following is
suggested for generating unique H measurement id's.\
\
measid = 10 \* site number + channel +
$\frac{\text{run number}}{\text{1000}}$\
\
where channel = 1 for Hx\
2 for Hy\
3 for Hz\
6 for short remote Rx (not part of another site)\
7 for short remote Ry (not part of another site)

3\. The CHTYPE option must be set to either HX, HY, or HZ. There is no
channel type RX or RY. Even if it is a reference, it must be an E or an
H.

4\. The coordinate of the H measurement is (X,Y). These options must be
filled in with the offsets of the H sensors relative to the reference
for the entire survey. For most MT surveys, it is sufficient to assume
that all H measurements are made at exactly the site location. Determine
the site offset as explained in hint 6 for \>=DEFINEMEAS above and use
this for the measurement offsets.

5\. The Z option does not need to be specified unless topography is
being taken into account.

6\. The AZM option must specify its azimuth measured clockwise from true
north. For Hz, the AZM option must be specified even though it has no
meaning unless the DIP option is also specified. This was done for
syntactic consistency among all the H measurements. Fill in zero in this
case.

7\. The options ACQCHAN, FILTER, GAIN, MEASDATE, and SENSOR may be
filled in for documentation purposes, but are optional.

#  10.0 Time Series Blocks

##  10.1 \>=TSERIESSECT

**Description:** Begins a time series data section. Defines the set of
measurements for which time series data are presented.

**Example:**

\>=TSERIESSECT\
SECTID=DEMO-1112\
NCHAN=10\
//10

111.001 112.001 113.001 114.001 115.001 121.001\
122.001 123.001 124.001 125.001

**Restrictions:** One or more instances of a \>=TSERIESSECT can appear
in an EDI file. Each one begins a new time series data section. It may
immediately follow the \>HEAD block, \>INFO block, and info text, or it
may appear after any other data section is complete.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

SECTID Identifying name for this section String or " " " "

NCHAN Number channels for time series data Integer \>=1 Required

MAXBLKS Max number of data blocks in section Integer \>=1 "16"

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NCHAN data values. Each
value is a measurement ID for a measurement defined in the \>=DEFINEMEAS
section. The ordering of the channels in the data set is the order used
for the time series data. The data set may not contain empty values
(Section 6.23). It may not be an empty data set and may not contain
binary data (Section 6.23).

**Notes:** 1. All data blocks within the section will contain time
series data for the set of measurements defined in this block.

2\. The dynamic default for NC is set by the NCHAN option.

3\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Because of the limits in formatting real numbers, care should be
exercised in writing and testing checksums.

4\. Because time series data are highly system dependent, a thorough
explanation of the data acquisition procedure and system response should
be included in the \>INFO block.

**Hints:** 1. Although this standard provides a framework to the
representation of time series data, it is not precisely defined due to
the many system dependencies associated with time series data. Agreement
between contractor and client is necessary to assure that the data is
usable.

2\. The \>INFO section should contain a full and accurate description of
the system dependencies in the data. Specifically, this should address
any calibration or system response which is present in the data.

3\. There should be sufficient information included in the file to
remove any system response and produce normalized spectra in standard
units.

##  10.2 \>TSERIES

**Description:** Single or multi-channel time series data.

**Example:**

\>TSERIES SECTID=b1-s12 NPTS=8 SR=288 // 80\
5744 -7834 45 4542 151 -3344\
23232 13243 1431 12567 -7879 7677\
-6568 7887 -67 178 -878 8008\
9854 -45 32078 4387 -7801 -567\
787 12057 -5870 23 9837 5437\
-5678 243 4580 -4874 46 25637\
3908 7699 -269 -8743 4370 -853\
659 -8759 -7807 329 -6539 4\
-5389 3790 12544 -20878 -67 -7546\
667 98 19875 6549 -7649 19984\
-78 -30199 -6787 -563 6430 -22900\
18220 7870 18 5439 -5292 7690\
-7809 4327 -6654 -78 6564 2316\
898 -9869

**Restrictions:** Zero or more \>TSERIES data blocks can appear within a
time series data section. A time series data section must begin with a
\>=TSERIESSECT data block which defines the set of measurements for
which time series data are given.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

SECTID Identifying name for this section String or " " " "

NCHAN Number of channels Integer \>=1 Dyn NC

NPTS Number of points/channel Integer \>=1 Required

SR Sample Rate (Hz) Number \>0 Required

MPX Multiplex type "TIME" or "CHAN" "CHAN"

BAND Name of frequency band String or " " " "

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Exactly (NCHAN x NPTS) data values are to be included in
the data set. The values must be within the legal range for reals. The
special value for no data (Section 6.23) should be used to denote
missing data values and the count should be set to zero (Section 6.23)
if the data set is empty.

**Notes:** 1. If the mpx option is MPX=TIME, then the data values
multiplexed in time. That is, they are ordered such that the first NCHAN
values correspond to the first sample for each of the channels (in the
order they appear in the \>=TSERIESSECT data set). The next NCHAN values
correspond to the second sample, and so on. If the mpx option is
MPX=CHAN, then the data values are channel multiplexed. That is, the
first NPTS values correspond to the time series data for the first
channel, the next NPTS values correspond to the second channel, and so
on.

2\. The sample rate at which the data was acquired is in Hz. A name for
the frequency band may be included using the band option. A complete
discussion of the units, calibration, filters, etc. for the acquisition
of time series data must be included in the \>INFO text.

3\. The dynamic default for NC was set by the NCHAN option in the
section head block.

4\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. Although this standard provides a framework to the
representation of time series data, it is not precisely defined due to
the many system dependencies associated with time series data. Agreement
between contractor and client is necessary to assure that the data is
usable.

2\. This is generally the only place where the use of a binary data file
(see Section 6.23) may be appropriate. Even for time series data, the
use of binary data is discouraged.

3\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

#  11.0 Spectra Blocks

##  11.1 \>=SPECTRASECT

**Description:** Begins a spectra data section. Defines the set of
measurements for which spectra data are presented.

**Example:**

\>=SPECTRASECT\
SECTID=DEMO-1112\
NCHAN=7\
NFREQ=25\
//7

111.001 112.001 113.001 114.001 115.001 121.001\
122.001

**Restrictions:** One or more instances of a \>=SPECTRASECT can appear
in an EDI file. Each one begins a new spectra data section. It may
immediately follow the \>HEAD block, \>INFO block, and info text, or it
may appear after any other data section is complete.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

SECTID Identifying name for this section String or " " " "

NCHAN Number channels for spectra data Integer \>=1 Required

NFREQ Number frequencies for spectra data Integer \>=1 Required

MAXBLKS Max number of data blocks in section Integer \>=1 "16"

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NCHAN data values. Each
value is a measurement ID for a measurement defined in the \>=DEFINEMEAS
section. The ordering of the channels in the data set is the order used
for the spectra data. The data set may not contain empty values (Section
6.23). It may not be an empty data set and may not contain binary data
(Section 6.23).

**Notes:** 1. All data blocks within the section will contain a complete
set of all auto and cross power spectra for the set of measurements
defined in this block.

2\. The dynamic default for NC is set by the NCHAN option.

3\. The dynamic default for NF is set by the NFREQ option.

4\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Because of the limits in formatting real numbers, care should be
exercised in writing and testing checksums.

**Hints:** 1. Stacked spectra provide a compact representation of the
data which still allows a great deal of flexibility in re-processing.
This is a recommended representation for archiving data. It represents a
compromise between re-processing flexibility and data compactness.

2\. Spectra segments allow all the reprocessing flexibility of stacked
spectra plus the ability to re-stack the spectra discarding or weighting
the various segments.

3\. The spectra model for EDI is based on a non-sparse matrix
representation. Any unavailable spectra terms must be filled in using
the "empty" data value (see Section 8.0). The order of the measurement
id's in the data set for this block defines the order of the
measurements which represent the rows and columns of the spectra matrix.

4\. Every measurement id in the data set for a \>=SPECTRASECT block must
be defined in the measurement definition section of that EDI file.

5\. Although data for multiple sites may be acquired as large spectra
matrices (10x10, 15x15, 16x16, or larger), it is recommended that the
contractor break this up into a separate spectra section for each site.
Each spectra section (for one site) will generally be a 5x5, 7x7, or 9x9
spectra depending on how many remote reference options are practical for
the site. By convention, when a spectra section corresponds to a single
site, the recommended order for the measurements is HX, HY, HZ, EX, EY,
RX1, RY1, RX2, RY2, \...

6\. The SECTID option for a section corresponding to the spectra for a
single site specifies the name to be associated with that site. The
recommended form is SSSSSSSS-NNN, where SSSSSSSS is the survey name and
NNN is the site number.

7\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

##  11.2 \>SPECTRA

**Description:** Auto and cross power spectra data.

**Example:**

\>SPECTRA SECTID=DEMO-11 FREQ=144 BW=36 AVGF=12 AVGT=128 //25

4.52746406E-07 -1.71115211E-08 -4.42694681E-09 -7.01830118E-07
-7.73957981E-06

4.36456673E-07 4.56306566E-08 -1.71640231E-08 3.09438576E-07
6.37708419E-09

5.58939155E-06 1.00488244E-07 -7.48501421E-08 2.94604973E-07
9.91281368E-09

-4.22392699E-09 4.54804372E-09 1.92081714E-07 2.60549939E-07
-5.23433918E-09

5.64745140E-09 -3.90451675E-07 -5.53199288E-06 -3.02203738E-08
2.29023019E-04

**Restrictions:** Zero or more \>SPECTRA data blocks can appear within a
spectra data section. A spectra data section must begin with a
\>=SPECTRASECT data block which defines the set of measurements for
which power spectra are given.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NCHAN Number of channels Integer \>=1 Dyn NC

FREQ Frequency (Hz) Number \>0 Required

ROTSPEC Rotation angle of spectra Angle or " " " "

BW Bandwidth (Hz) Number \>0 Required

AVGT Number of independent avgs in time Number \>0 "1"

AVGF Number of independent avgs in freq Number \>0 "1"

BAND Name of frequency band String or " " " "

SEGNUM Number identifying a partial spectra Integer \>=0 "0"

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Exactly (NCHAN x NCHAN) data values are to be included in
the data set. The data set represents an estimate of the auto and cross
power spectra for a set of NCHAN measurements over a particular
frequency range. The values must be within the legal range for reals.
The special value for empty data (Section 6.23) should be used to denote
missing data values and the count should be set to zero (Section 6.23)
if the data set is empty. The values are packed as described in note
below.

**Notes:** 1. Crosspower matrices are Hermitian and can be packed as
shown in the following example. The complex auto and cross power spectra
for 4 channels A, B, C, and D:

> A B C D\
> A \<AA\*\> \<AB\*\> \<AC\*\> \<AD\*\>\
> B \<BA\*\> \<BB\*\> \<BC\*\> \<BD\*\>\
> C \<CA\*\> \<CB\*\> \<CC\*\> \<CD\*\>\
> D \<DA\*\> \<DB\*\> \<DC\*\> \<DD\*\>

can be stored as follows:

> A B C D\
> A \<AA\*\> Imag\<AB\*\> Imag\<AC\*\> Imag\<AD\*\>\
> B Real\<AB\*\> \<BB\*\> Imag\<BC\*\> Imag\<BD\*\>\
> C Real\<AC\*\> Real\<BC\*\> \<CC\*\> Imag\<CD\*\>\
> D Real\<AD\*\> Real\<BD\*\> Real\<CD\*\> \<DD\*\>

with the real part in the lower left triangle and the imaginary part in
the upper right triangle. Note that the auto spectra are real. The only
ambiguity is the sign of the imaginary values. This is defined such that
the sign associated with the imaginary values is in the upper right
triangle of the original matrix is preserved in the compressed matrix.
The data set is this compressed matrix, read by row, e.g. \<AA\*\>,
Imag\<AB\*\>, Imag\<AC\*\>, \... Real\<CD\*\>, \<DD\*\>.

2\. The ordered set of measurements for which spectra are being given is
defined by the \>=SPECTRASECT block. The ordered list of measurements
corresponds to the ordered list "A,B,C,D" in the example above.

3\. The value of the FREQ option gives the center frequency of the
spectra estimates in Hz. The BW option specifies the bandwidth in Hz
between the (half-power) cut-off frequencies.

4\. The value of the AVGT option is the number of independent estimates
in time which were averaged to make these spectra estimates. Cascade
decimation averages constant percentage bandwidth spectra estimates
which are independent in time. Weighted averaging can lead to a number
of independent samples which is not an integer. The AVGF option is the
number of independent estimates in frequency which were averaged to make
these spectra estimates. Spectra estimates generated from an FFT are
averaged in frequency to produce constant percentage bandwidth spectra.
Note that if a number of FFT runs are averaged, both AVGT and AVGF can
be greater than 1.

5\. If the ROTSPEC option is omitted, the spectra are assumed to be in
the measurement directions. If the option is included, it must be an
angle representing the (average) rotation angle of the type Ex and Hx
channels from true north and the type Ey and Hy channels from east. If
sensor layouts are orthogonal, rotation transformations can be applied
to all of the horizontal sensor pairs to rotate the spectra. However, if
the sensors are not all layed out orthogonally, the meaning of ROTSPEC
should be explained in the \>INFO text.

6\. If the SEGNUM option is omitted, or is zero, then the spectra are
assumed to be final averages. The SEGNUM option allows delivery of
partial spectra estimates, which can then be averaged as desired to
effect a form of data editing. Note that delivery of spectra segments
greatly increases the quantity of data.

7\. The dynamic default for NC was set by the NCHAN option in the
section head block.

8\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. Efforts to standardize sign and conjugation standards for
spectra have been hampered by different conventions for sensor polarity,
amplifier response, and even Fourier transform definition. Generally,
computation of standard MT parameters should produce a phase for the xy
component in the first quadrant and a phase for the yx component in the
third quadrant.

2\. There are at least four combinations of spectra sign and conjugation
which produce correct rho values and phase quadrants. These different
combinations lead to (among other things) different variances (error
bars). Only one of these combinations is actually correct. Believable
predicted coherencies have proved to be a reasonably good indicator of
the correct combination of sign and conjugation.

3\. Although the spectra blocks within a spectra section may be in any
order, it is recommended that they be in monotonically descending order
of frequency.

4\. The preferred rotation for spectra is that all components be rotated
such that the x components correspond to true north. A less desirable
alternative is to rotate the spectra for the reference measurements to
be aligned with the azimuth for the site and to specify the azimuth of
the site. The least desirable alternative is to deliver spectra in
measurement directions.

5\. For FTT based processing , AVGF is the number of harmonics averaged
and AVGT is the (weighted) number of FFT records stacked. For cascade
decimation based processing, AVGF is 1 and AVFT is the (weighted) number
of DFT records averaged.

#  12.0 MT, EMAP, and Other Section head blocks

##  12.1 \>=MTSECT

**Description:** Begins an MT data section. Defines the default
measurements for an MT sounding.

**Example:**

\>=MTSECT\
SECTID=DEMO-11\
NFREQ=40\
HX=111.003\
HY=112.003\
HZ=113.003\
EX=113.003\
RX=121.003\
RY=122.003

**Restrictions:** One or more instances of an \>=MTSECT can appear in an
EDI file. Each one begins a new MT data section. It may immediately
follow the \>HEAD block, \>INFO block, and info text, or it may appear
after any other data section is complete.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

SECTID Identifying name for this section String or " " " "

NFREQ Number of frequencies Integer \>=1 Required

MAXBLKS Maximum number of blocks in section Integer \>=1 "64"

HX Meas ID for Hx measurement Def Meas ID or " " " "

HY Meas ID for Hy measurement Def Meas ID or " " " "

HZ Meas ID for Hz measurement Def Meas ID or " " " "

EX Meas ID for Ex measurement Def Meas ID or " " " "

EY Meas ID for Ey measurement Def Meas ID or " " " "

RX Meas ID for Rx ref measurement Def Meas ID or " " " "

RY Meas ID for Ry ref measurement Def Meas ID or " " " "

**Data Set:** None

**Notes:** 1. The dynamic defaults for HX, HY, HZ, EX, EY, RX, and RY
may be set by the \>=MTSECT block. If any are not specified, the
corresponding dynamic default is set to " ". All of the data blocks
within the section may use these dynamic defaults if the corresponding
options are not specified. After application of any appropriate dynamic
defaults, an option argument will be a defined measurement ID or it may
be " ", indicating no measurement.

2\. Although no restrictions are enforced, all appropriate measurements
should be defined for a given data block. For scalar MT, only one E and
one H are required (e.g. Ey and Hx). For tensor MT, two E's and two H's
are required. If tipper parameters are being computed, Hz must also be
defined. If least-squares estimation of the impedances is used, the
reference measurements Rx and Ry must be indicated. This is true whether
they are coincident with other measurements (local reference) or
distinct (remote reference).

3\. Under normal circumstances, the measurements for HX, HY, HZ, EX, EY,
RX, and RY should be the same for all data blocks within an \>=MTSECT
data section.

4\. The dynamic default for NF is set to the value of the NFREQ option.

**Hints:** 1. Computed MT parameters provide a representation of the
data which requires no additional processing. This is a recommended
representation for archiving data because it can be readily used by
anyone without requiring MT processing capability.

2\. The SECTID option for a section corresponding to the computed
parameters for a site specifies the name to be associated with that
site. The recommended form is SSSSSSSS-NNN, where SSSSSSSS is the survey
name and NNN is the site number.

3\. If there are blocks for more than 64 computed parameters included
for this site, then the MAXBLKS option should be set to an appropriate
value.

4\. The HX, HY, HZ, EX, EY, RX, RY, and NREQ options should be specified
for the \>=MTSECT block. These then become the dynamic defaults for all
blocks within that section. If specified here, they do not need to be
re-specified for other blocks in the section.

##  12.2 \>=EMAPSECT

**Description:** Begins an EMAP data section. Defines the measurements
which make up an EMAP line.

**Example:**

\>=EMAPSECT\
SECTID=linea\
NFREQ=40\
NDIPOLE=8\
HX=11.005\
HY=12.005\
RX=21.005\
RY=22.005\
//8\
314.005 324.005 334.005 344.005 354.005 364.005\
374.005 384.005

**Restrictions:** One or more instances of an \>=EMAPSECT can appear in
an EDI file. Each one begins a new EMAP data section. It may immediately
follow the \>HEAD block, \>INFO block, and info text, or it may appear
after any other data section is complete.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

SECTID Identifying name for this section String or " " " "

NFREQ Number of frequencies Integer \>=1 Required

MAXBLKS Maximum number of blocks in section Integer \>=1 "64"

NDIPOLE Number of dipoles in the EMAP line Integer \>=1 Required

TYPE Descr of spatial filter type used String or " " " "

HX Meas ID for Hx measurement Def Meas ID or " " " "

HY Meas ID for Hy measurement Def Meas ID or " " " "

RX Meas ID for Rx ref measurement Def Meas ID or " " " "

RY Meas ID for Ry ref measurement Def Meas ID or " " " "

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NDIPOLE data values. Each
value is a measurement ID for a measurement defined in the \>=DEFINEMEAS
section. The ordering of the measurements in the data defines the
measurements which make up the EMAP line. The type of all of the
measurement ID's (as defined by the CHTYPE option in the corresponding
\>EMEAS block) should be EX, although this restriction is not enforced.
The data set may not contain empty values; nor may it be an empty data
set and or contain binary data (Section 6.23).

**Notes:** 1. The dynamic defaults for HX, HY, RX, and RY may be set by
the \>=EMAPSECT block. If any are not specified, the corresponding
dynamic default is set to " ". All of the data blocks within the section
may use these dynamic defaults if the corresponding options are not
specified. After application of any appropriate dynamic defaults, an
option argument will be a defined measurement ID or it may be " ",
indicating no measurement.

2\. Although no restrictions are enforced, all appropriate measurements
should be defined for a given data block. For synthetic EMAP only Hx is
required for parallel parameters and only Hy is required for
perpendicular parameters. However, for field data, where the line layout
is not perfectly straight, both Hx and Hy are generally required. If
least-squares estimation of the impedances is used, the reference
measurements Rx and Ry must be indicated. This is true whether they are
coincident with other measurements (local reference) or distinct (remote
reference).

3\. Under normal circumstances, the measurements for HX, HY, EX, RX, and
RY should be the same for all data blocks corresponding to a given span
within the \>=EMAPSECT data section.

4\. The TYPE option gives the filter type for spatial filter used; for
example, "HANNING". If explanation is required, it should be included in
the \>INFO section.

5\. The dynamic default for NF is set to the value of the NFREQ option.

6\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Because of the limits in formatting real numbers, care should be
exercised in writing and testing checksums.

**Hints:** 1. Computed EMAP parameters provide a representation of the
data which requires no additional processing. This is a recommended
representation for archiving data because it can be readily used by
anyone without requiring MT processing capability.

2\. The SECTID option for a section corresponding to the computed
parameters for a site specifies the name to be associated with that
dipole. The recommended form is SSSSSSSS-NNN, where SSSSSSSS is the
survey name and NNN is the dipole number.

3\. If there are blocks for more than 64 computed parameters included
for this dipole, then the MAXBLKS option should be set to an appropriate
value.

4\. The Hx, Hy, Rx, Ry, and Nfreq options should be specified for the
\>=EMAPSECT block. These then become the dynamic defaults for all blocks
within that section. If specified here, they do not need to be
re-specified for other blocks in the section.

5\. The data section for this block is an ordered list of the
measurement id's which make up the line of dipoles.

6\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

##  12.3 \>=OTHERSECT

**Description:** Begins an OTHER data section. Defines default
measurements and a set of ordered measurements.

**Example:**

\>=OTHERSECT\
SECTID=DEMO-100\
NFREQ=40\
N=6\
HX=11.007\
HY=12.007\
EX=14.007\
EY=15.007\
//6\
314.007 324.007 334.007 344.007 354.007 364.007

**Restrictions:** One or more instances of an \>=OTHERSECT can appear in
an EDI file. Each one begins a new MT data section. It may immediately
follow the \>HEAD block, \>INFO block, and info text, or it may appear
after any other data section is complete.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

SECTID Identifying name for this section String or " " " "

NFREQ Number of frequencies Integer \>=1 Required

MAXBLKS Maximum number of blocks in section Integer \>=1 "64"

N Number of meas ID's in the ordered set Integer \>=0 "0"

HX Meas ID for Hx measurement Def Meas ID or " " " "

HY Meas ID for Hy measurement Def Meas ID or " " " "

HZ Meas ID for Hz measurement Def Meas ID or " " " "

EX Meas ID for Ex measurement Def Meas ID or " " " "

EY Meas ID for Ey measurement Def Meas ID or " " " "

RX Meas ID for Rx ref measurement Def Meas ID or " " " "

RY Meas ID for Ry ref measurement Def Meas ID or " " " "

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly N data values, although N
may be zero. Each value is a measurement ID for a measurement defined in
the \>=DEFINEMEAS section. The ordering of the measurements in the data
defines the measurements which make up any ordered set of measurements
such as an EMAP line. The type of all of the measurement ID's (as
defined by the CHTYPE option in the corresponding \>EMEAS or \>HMEAS
block) may be anything. The data set may not contain empty values; nor
may it be an empty data set or contain binary data (Section 6.23).

**Notes:** 1. The dynamic defaults for HX, HY, HZ, EX, EY, RX, and RY
may be set by the \>=OTHERSECT block. If any are not specified, the
corresponding dynamic default is set to " ". All of the data blocks
within the section may use these dynamic defaults if the corresponding
options are not specified. After application of any appropriate dynamic
defaults, an option argument will be a defined measurement ID or it may
be " ", indicating no measurement. Although no restrictions are
enforced, all appropriate measurements should be defined for a given
data block.

2\. The dynamic default for NF is set to the value of the NFREQ option.

3\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Because of the limits in formatting real numbers, care should be
exercised in writing and testing checksums.

#  13.0 Impedance Data Blocks

##  13.1 \>ZXXR, \>ZXXI, ZXXR.VAR, \>ZXXI.VAR, \>ZXX.VAR, \>ZXX.COV

**Description:** \>ZXXR Real component of impedance Z

\>ZXXI Imaginary component of impedance Z

\>ZXXR.VAR Variance of real component of impedance Z

\>ZXXI.VAR Variance of imaginary component of impedance Z

\>ZXX.VAR Variance of impedance Z

\>ZXX.COV Covariance of impedance Z

**Example:**

\>ZXXR ROT=ZROT // 20

6.01820767E-01 7.74375319E-01 5.08936584E-01 4.09464180E-01
3.14963371E-01

2.60999680E-01 2.38515064E-01 2.67349362E-01 2.46229470E-01
1.61181539E-01

1.14646673E-01 9.87800136E-02 -5.15134633E-01 -1.03739366E-01
2.51554072E-01

1.23188727E-01 -7.75714070E-02 2.89261997E-01 1.84981659E-01
-1.65735200E-01

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT or \>=EMAPSECT data section. Any impedance blocks
in these sections must immediately follow the \>FREQ block and the
optional \>ZROT block, if included. One or more of any or all may appear
anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

TYPE Type of estimation used String or " " "LEASTSQ"

ROT Type of rotation applied "NONE", "NORTH",\
or "ZROT" "NONE"

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

EX Meas ID for Ex measurement Def Meas ID or " " Dyn EX

EY Meas ID for Ey measurement Def Meas ID or " " Dyn EY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. If the ROT option is "ZROT" then the impedances are
assumed to have been rotated to the angles indicated in the \>ZROT data
block. If it is "NORTH", they are assumed to have been rotated to true
north. If it is "NONE", they are assumed to be in the measurement
directions. Only tensor impedances (see note below) may be rotated.

2\. The dynamic defaults for HX, HY, EX, EY, RX, and RY were set by the
\>=MTSECT, \>=EMAPSECT, or \>=OTHERSECT block. If any were not
specified, the corresponding dynamic default was set to " ". All of
these options (after application of dynamic defaults) may be " ",
indicating no measurement. Although no restrictions are enforced, all
appropriate measurements should be defined. For each scalar impedance
only one E and one H are required (e.g. Ex and Hx for ZXX). For tensor
impedances, two E's and two H's are required. If least-squares
estimation was used, the reference measurements Rx and Ry must be
indicated. This is true whether they are coincident with other
measurements (local reference) or distinct (remote reference).

3\. The dynamic default for NF was set by the NFREQ option in the
section head block.

4\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. For MT data, it is recommended that impedances be
delivered rotated to maximize one of the criteria described in Section
5.8. In this case, this rotation angle must be specified in a \>ZROT
block which must appear previously. For EMAP data, it is recommended
that impedances be delivered in measurement directions.

2\. Generally the HX, HY, EX, EY, RX, RY, and NFREQ options will be
provided by the \>=MTSECT or \>=EMAPSECT block through the dynamic
default mechanism.

3\. An EDI file should provide either the total variance (ZXX.VAR) or
the real, imaginary and covariance (ZXXR.VAR, ZXXI.VAR, and ZXX.COV),
but not both.

4\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

##  13.2 \>ZXYR, \>ZXYI, ZXYR.VAR, \>ZXYI.VAR, \>ZXY.VAR, \>ZXY.COV

**Description:** \>ZXYR Real component of impedance Z\
\>ZXYI Imaginary component of impedance Z\
\>ZXYR.VAR Variance of real component of impedance Z\
\>ZXYI.VAR Variance of imaginary component of impedance Z\
\>ZXY.VAR Variance of impedance Z\
\>ZXY.COV Covariance of impedance Z

**Example:**

\>ZXYR ROT=ZROT // 20

1.82304420E+01 1.58144493E+01 1.27437716E+01 1.13909054E+01
9.03257847E+00

7.78446531E+00 5.97235203E+00 4.77245998E+00 3.46459270E+00
3.04857588E+00

2.71974206E+00 2.15195584E+00 1.05662036E+00 1.92158365E+00
2.20907617E+00

1.70448887E+00 1.45904374E+00 1.43950450E+00 8.96938622E-01
9.33596849E-01

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT or \>=EMAPSECT data section. Any impedance blocks
in these sections must immediately follow the \>FREQ block and the
optional \>ZROT block, if included. One or more of any or all may appear
anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

TYPE Type of estimation used String or " " "LEASTSQ"

ROT Type of rotation applied "NONE", "NORTH",\
or "ZROT" "NONE"

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

EX Meas ID for Ex measurement Def Meas ID or " " Dyn EX

EY Meas ID for Ey measurement Def Meas ID or " " Dyn EY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. If the ROT option is "ZROT" then the impedances are
assumed to have been rotated to the angles indicated in the \>ZROT data
block. If it is "NORTH", they are assumed to have been rotated to true
north. If it is "NONE", they are assumed to be in the measurement
directions. Only tensor impedances (see note 2 below) may be rotated.

2\. The dynamic defaults for HX, HY, EX, EY, RX, and RY were set by the
\>=MTSECT, \>=EMAPSECT, or \>=OTHERSECT block. If any were not
specified, the corresponding dynamic default was set to " ". All of
these options (after application of dynamic defaults) may be " ",
indicating no measurement. Although no restrictions are enforced, all
appropriate measurements should be defined. For each scalar impedance
only one E and one H are required (e.g. Ex and Hy for ZXY). For tensor
impedances, two E's and two H's are required. If least-squares
estimation was used, the reference measurements Rx and Ry must be
indicated. This is true whether they are coincident with other
measurements (local reference) or distinct (remote reference).

3\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

4\. The CHKSUM, if specified, option may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. For MT data, it is recommended that impedances be
delivered rotated to maximize one of the criteria described in Section
5.8. In this case, this rotation angle must be specified in a \>ZROT
block which must appear previously. For EMAP data, it is recommended
that impedances be delivered in measurement directions.

2\. Generally the HX, HY, EX, EY, RX, RY, and NFREQ options will be
provided by the \>=MTSECT or \>=EMAPSECT block through the dynamic
default mechanism.

3\. An EDI file should provide either the total variance (ZXY.VAR) or
the real, imaginary and covariance (ZXYR.VAR, ZXYI.VAR, and ZXY.COV),
but not both.

4\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

##  13.3 \>ZYXR, \>ZYXI, ZYXR.VAR, \>ZYXI.VAR, \>ZYX.VAR, \>ZYX.COV

**Description:** \>ZYXR Real component of impedance Z\
\>ZYXI Imaginary component of impedance Z\
\>ZYXR.VAR Variance of real component of impedance Z\
\>ZYXI.VAR Variance of imaginary component of impedance Z\
\>ZYX.VAR Variance of impedance Z\
\>ZYX.COV Covariance of impedance Z

**Example:**

\>ZYXR ROT=ZROT // 20

-1.83230228E+01 -1.51980267E+01 -1.23099728E+01 -1.02583351E+01
-8.56172848E+00

-6.79286957E+00 -4.86690569E+00 -3.88225937E+00 -2.75575304E+00
-2.31945348E+00

-1.89399958E+00 -1.41652894E+00 -1.46898735E+00 -1.60360003E+00
-1.37504911E+00

-3.73708814E-01 -6.21191323E-01 -5.30263722E-01 -3.15491974E-01
-5.12749434E-01

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT data section. They may not appear in an
\>=EMAPSECT data section. Any impedance blocks must immediately follow
the \>FREQ block and the optional \>ZROT block, if included. One or more
of any or all may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

TYPE Type of estimation used String or " " "LEASTSQ"

ROT Type of rotation applied "NONE", "NORTH",\
or "ZROT" "NONE"

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

EX Meas ID for Ex measurement Def Meas ID or " " Dyn EX

EY Meas ID for Ey measurement Def Meas ID or " " Dyn EY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. If the ROT option is "ZROT" then the impedances are
assumed to have been rotated to the angles indicated in the \>ZROT data
block. If it is "NORTH", they are assumed to have been rotated to true
north. If it is "NONE", they are assumed to be in the measurement
directions. Only tensor impedances (see note 2 below) may be rotated.

2\. The dynamic defaults for HX, HY, EX, EY, RX, and RY were set by the
\>=MTSECT, or \>=OTHERSECT block. If any were not specified, the
corresponding dynamic default was set to " ". All of these options
(after application of dynamic defaults) may be " ", indicating no
measurement. Although no restrictions are enforced, all appropriate
measurements should be defined. For each scalar impedance only one E and
one H are required (e.g. Ey and Hx for ZYX). For tensor impedances, two
E's and two H's are required. If least-squares estimation was used, the
reference measurements Rx and Ry must be indicated. This is true whether
they are coincident with other measurements (local reference) or
distinct (remote reference).

3\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

4\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. For MT data, it is recommended that impedances be
delivered rotated to maximize one of the criteria described in Section
5.8. In this case, this rotation angle must be specified in a \>ZROT
block which must appear previously. For EMAP data, it is recommended
that impedances be delivered in measurement directions.

2\. Generally the HX, HY, EX, EY, RX, RY, and NFREQ options will be
provided by the \>=MTSECT or \>=EMAPSECT block through the dynamic
default mechanism.

3\. An EDI file should provide either the total variance (ZYX.VAR) or
the real, imaginary and covariance (ZYXR.VAR, ZYXI.VAR, and ZYX.COV),
but not both.

4\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

##  13.4 \>ZYYR, \>ZYYI, ZYYR.VAR, \>ZYYI.VAR, \>ZYY.VAR, \>ZYY.COV

**Description:** \>ZYYR Real component of impedance Z\
\>ZYYI Imaginary component of impedance Z\
\>ZYYR.VAR Variance of real component of impedance Z\
\>ZYYI.VAR Variance of imaginary component of impedance Z\
\>ZYY.VAR Variance of impedance Z\
\>ZYY.COV Covariance of impedance Z

**Example:**

\>ZYYR ROT=ZROT // 20

-4.14399713E-01 3.37689847E-01 -1.36755705E-01 -7.88401291E-02
2.10223034E-01

2.23552525E-01 2.38290370E-01 2.43170977E-01 2.11295232E-01
1.55212507E-01

1.09562479E-01 9.46080014E-02 9.78896096E-02 4.17534620E-01
3.39732528E-01

2.83228546E-01 -3.45761515E-02 5.55908121E-02 -2.84877960E-02
1.25025302E-01

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT data section. They may not appear in an
\>=EMAPSECT data section. Any impedance blocks must immediately follow
the \>FREQ block and the optional \>ZROT block, if included. One or more
of any or all may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

TYPE Type of estimation used String or " " "LEASTSQ"

ROT Type of rotation applied "NONE", "NORTH",\
or "ZROT" "NONE"

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

EX Meas ID for Ex measurement Def Meas ID or " " Dyn EX

EY Meas ID for Ey measurement Def Meas ID or " " Dyn EY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. If the ROT option is "ZROT" then the impedances are
assumed to have been rotated to the angles indicated in the \>ZROT data
block. If it is "NORTH", they are assumed to have been rotated to true
north. If it is "NONE", they are assumed to be in the measurement
directions. Only tensor impedances (see note 2 below) may be rotated.

2\. The dynamic defaults for HX, HY, EX, EY, RX, and RY were set by the
\>=MTSECT, or \>=OTHERSECT block. If any were not specified, the
corresponding dynamic default was set to " ". All of these options
(after application of dynamic defaults) may be " ", indicating no
measurement. Although no restrictions are enforced, all appropriate
measurements should be defined. For each scalar impedance only one E and
one H are required (e.g. Ey and Hy for ZYY). For tensor impedances, two
E's and two H's are required. If least-squares estimation was used, the
reference measurements Rx and Ry must be indicated. This is true whether
they are coincident with other measurements (local reference) or
distinct (remote reference).

3\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

4\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. For MT data, it is recommended that impedances be
delivered rotated to maximize one of the criteria described in Section
5.8. In this case, this rotation angle must be specified in a \>ZROT
block which must appear previously. For EMAP data, it is recommended
that impedances be delivered in measurement directions.

2\. Generally the HX, HY, EX, EY, RX, RY, and NFREQ options will be
provided by the \>=MTSECT or \>=EMAPSECT block through the dynamic
default mechanism.

3\. An EDI file should provide either the total variance (ZYY.VAR) or
the real, imaginary and covariance (ZYYR.VAR, ZYYI.VAR, and ZYY.COV),
but not both.

4\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

##  13.5 \>FZXXR, \>FZXXI, \>FZXYR, \>FZXYI

**Description:** \>FZXXR Real component of spatially filtered impedance
Z\
\>FZXXI Imaginary component of spatially filtered impedance Z\
\>FZXYR Real component of spatially filtered impedance Z\
\>FZXYI Imaginary component of spatially filtered impedance Z

**Example:**

\>FZYXR ROT=ZROT // 20

-1.83230228E+01 -1.51980267E+01 -1.23099728E+01 -1.02583351E+01
-8.56172848E+00

-6.79286957E+00 -4.86690569E+00 -3.88225937E+00 -2.75575304E+00
-2.31945348E+00

-1.89399958E+00 -1.41652894E+00 -1.46898735E+00 -1.60360003E+00
-1.37504911E+00

-3.73708814E-01 -6.21191323E-01 -5.30263722E-01 -3.15491974E-01
-5.12749434E-01

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=EMAPSECT data section. They may not appear in an
\>=MTSECT data section. Any impedance blocks must immediately follow the
\>FREQ block. One or more of any or all may appear anywhere in
\>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

TYPE Type of estimation used String or " " "LEASTSQ"

ROT Type of rotation applied "NONE", "NORTH",\
or "ZROT" "NONE"

EX Meas ID for Ex measurement Defined Meas ID Required

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. The dynamic defaults for HX, HY, RX, and RY were set by
the \>=EMAPSECT, or \>=OTHERSECT block. If any were not specified, the
corresponding dynamic default was set to " ". All of these options
(after application of dynamic defaults) may be " ", indicating no
measurement. Although no restrictions are enforced, all appropriate
measurements should be defined. For each scalar impedance one E and one
H are required (e.g. Ex and Hx for ZXX, Ex and Hy for ZXY). If
least-squares estimation was used, the reference measurements Rx and Ry
must be indicated. This is true whether they are coincident with other
measurements (local reference) or distinct (remote reference).

2\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

3\. For EMAP filtered impedances, the ROT option should be "NONE",
indicating that the impedances correspond to the measurement directions.

4\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. For EMAP data, it is recommended that impedances be
delivered in measurement directions.

2\. Generally the HX, HY, EX, EY, RX, RY, and NFREQ options will be
provided by the \>=EMAPSECT block through the dynamic default mechanism.

3\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

#  14.0 Apparent Resistivity and Phase Data Blocks

##  14.1 \>RHOXX, \>PHSXX, \>RHOXX.VAR, \>PHSXX.VAR \>RHOXX.ERR, \>PHSXX.ERR, \>RHOXX.FIT, \>PHSXX.FIT

**Description:** \>RHOXX Magnitude of apparent resistivity (W-m)
computed from Z\
\>PHSXX Phase angle of apparent resistivity (deg) computed from Z\
\>RHOXX.VAR Variance of Rhocomputed from variances of real and imag
parts of Z\
\>PHSXX.VAR Variance of Phscomputed from variances of real and imag
parts of Z\
\>RHOXX.ERR Logerror bar (in decades) assoc. with Rho\
\>PHSXX.ERR Error bar (in degrees) assoc. with Phs\
\>RHOXX.FIT Data values defining smoothed curve which fits the Rhodata\
\>PHSXX.FIT Data values defining smoothed curve which fits the Phxdata

**Example:**

\>RHOXX ROT=RHOROT // 20

1.08579102E+01 1.09430246E+01 1.05040903E+01 1.13740978E+01
1.04564753E+01

1.09703875E+01 1.08448954E+01 1.03996630E+01 9.13816547E+00
8.84461498E+00

8.36482430E+00 8.65559006E+00 9.26512432E+00 6.76110649E+00
1.29676619E+01

1.17602291E+01 1.24114132E+01 2.58277512E+01 1.86857986E+01
1.18354082E+01

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT or \>=EMAPSECT data section. Any apparent
resistivity blocks in these sections must follow the \>FREQ block, any
impedance blocks, and the optional \>RHOROT block, if included. One or
more of any or all may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

TYPE Confidence % for .ERR data or String or " " " "

fitting method for .FIT data

ROT Type of rotation applied "NONE", "NORTH",\
or "RHOROT" "NONE"

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

EX Meas ID for Ex measurement Def Meas ID or " " Dyn EX

EY Meas ID for Ey measurement Def Meas ID or " " Dyn EY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. If the ROT option is "RHOROT" then the apparent
resistivities are assumed to have been rotated to the angles indicated
in the \>RHOROT data block. If it is "NORTH", they are assumed to have
been rotated to true north. If it is "NONE", they are assumed to be in
the measurement directions. Only apparent resistivities computed from
tensor impedances (see note 2 below) may be rotated.

2\. The dynamic defaults for HX, HY, EX, EY, RX, RY were set by the
\>=MTSECT, \>=EMAPSECT, or \>=OTHERSECT block. If any were not
specified, the corresponding dynamic default was set to " ". All of
these options (after application of dynamic defaults) may be " ",
indicating no measurement. Although no restrictions are enforced, all
appropriate measurements should be defined. For each apparent
resistivity computed from a scalar impedance only one E and one H are
required (e.g. Ex and Hx for RHOXX). For rotatable apparent
resistivities two E's and two H's are required. If least-squares
estimation was used for the impedances, the reference measurements Rx
and Ry must be indicated. This is true whether they are coincident with
other measurements (local reference) or distinct (remote reference).

3\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

4\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. For MT data, it is recommended that rho's be delivered
rotated to maximize one of the criteria described in Section 5.8. In
this case, this rotation angle must be specified in a \>RHOROT block
which must appear previously. For EMAP data, it is recommended that
rho's be delivered in measurement directions.

2\. Generally the HX, HY, EX, EY, RX, RY, and NFREQ options will be
provided by the \>=MTSECT or \>=EMAPSECT block through the dynamic
default mechanism.

3\. The \>RHOXX.ERR block gives the size (in decades) of the error bars
representing +/- one standard deviation of log10(rho). This error bar is
symmetrical in log10(rho) space.

4\. The \>RHOXX.FIT block may be optionally included to specify a smooth
or interpreted curve to be associated with the raw data.

5\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

##  14.2 \>RHOXY, \>PHSXY, \>RHOXY.VAR, \>PHSXY.VAR \>RHOXY.ERR, \>PHSXY.ERR, \>RHOXY.FIT, \>PHSXY.FIT

**Description:** \>RHOXY Magnitude of apparent resistivity (W-m)
computed from Z\
\>PHSXY Phase angle of apparent resistivity (deg) computed from Z\
\>RHOXY.VAR Variance of Rhocomputed from variances of real and imag
parts of Z\
\>PHSXY.VAR Variance of Phscomputed from variances of real and imag
parts of Z\
\>RHOXY.ERR Logerror bar (in decades) assoc. with Rho\
\>PHSXY.ERR Error bar (in degrees) assoc. with Phs\
\>RHOXY.FIT Data values defining smoothed curve which fits the Rhodata\
\>PHSXY.FIT Data values defining smoothed curve which fits the Phsdata

**Example:**

\>RHOXY ROT=RHOROT // 20

1.08579102E+01 1.09430246E+01 1.05040903E+01 1.13740978E+01
1.04564753E+01

1.09703875E+01 1.08448954E+01 1.03996630E+01 9.13816547E+00
8.84461498E+00

8.36482430E+00 8.65559006E+00 9.26512432E+00 6.76110649E+00
1.29676619E+01

1.17602291E+01 1.24114132E+01 2.58277512E+01 1.86857986E+01
1.18354082E+01

\>PHSXY ROT=RHOROT // 20

4.44184723E+01 4.45486832E+01 4.41194191E+01 4.45983124E+01
4.38439178E+01

4.55155830E+01 4.85306206E+01 5.13925629E+01 5.37120476E+01
5.23208351E+01

4.66266098E+01 5.19162025E+01 6.89909592E+01 2.81978683E+01
2.63625183E+01

3.30418930E+01 3.11888943E+01 4.74999847E+01 5.26897507E+01
2.37417355E+01

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT or \>=EMAPSECT data section. Any apparent
resistivity blocks in these sections must follow the \>FREQ block, any
impedance blocks, and the optional \>RHOROT block, if included. One or
more of any or all may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

TYPE Confidence % for .ERR data or String or " " " "\
fitting method for .FIT data.

ROT Type of rotation applied "NONE", "NORTH",\
or "RHOROT" "NONE"

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

EX Meas ID for Ex measurement Def Meas ID or " " Dyn EX

EY Meas ID for Ey measurement Def Meas ID or " " Dyn EY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. If the ROT option is "RHOROT" then the apparent
resistivities are assumed to have been rotated to the angles indicated
in the \>RHOROT data block. If it is "NORTH", they are assumed to have
been rotated to true north. If it is "NONE", they are assumed to be in
the measurement directions. Only apparent resistivities computed from
tensor impedances (see note below) may be rotated.

2\. The dynamic defaults for HX, HY, EX, EY, RX, and RY were set by the
\>=MTSECT, \>=EMAPSECT, or \>=OTHERSECT block. If any were not
specified, the corresponding dynamic default was set to " ". All of
these options (after application of dynamic defaults) may be " ",
indicating no measurement. Although no restrictions are enforced, all
appropriate measurements should be defined. For each apparent
resistivity computed from a scalar impedance only one E and one H are
required (e.g. Ex and Hy for RHOXY). For rotatable apparent
resistivities two E's and two H's are required. If least-squares
estimation was used for the impedances, the reference measurements Rx
and Ry must be indicated. This is true whether they are coincident with
other measurements (local reference) or distinct (remote reference).

3\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

4\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. For MT data, it is recommended that rho's be delivered
rotated to maximize one of the criteria described in Section 5.8. In
this case, this rotation angle must be specified in a \>RHOROT block
which must appear previously. For EMAP data, it is recommended that
rho's be delivered in measurement directions.

2\. Generally the HX, HY, EX, EY, RX, RY, and NFREQ options will be
provided by the \>=MTSECT or \>=EMAPSECT block through the dynamic
default mechanism.

3\. The \>RHOXY.ERR block gives the size (in decades) of the error bars
representing +/- one standard deviation of log10(rho). This error bar is
symmetrical in log10(rho) space.

4\. The \>RHOXY.FIT block may be optionally included to specify a smooth
or interpreted curve to be associated with the raw data.

5\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

##  14.3 \>RHOYX, \>PHSYX, \>RHOYX.VAR, \>PHSYX.VAR \>RHOYX.ERR, \>PHSYX.ERR, \>RHOYX.FIT, \>PHSYX.FIT

**Description:** \>RHOYX Magnitude of apparent resistivity (W-m)
computed from Z\
\>PHSYX Phase angle of apparent resistivity (deg) computed from Z\
\>RHOYX.VAR Variance of Rhocomputed from variances of real and imag
parts of Z\
\>PHSYX.VAR Variance of Phscomputed from variances of real and imag
parts of Z\
\>RHOXY.ERR Logerror bar (in decades) assoc. with Rho\
\>PHSXY.ERR Error bar (in degrees) assoc. with Phs\
\>RHOXY.FIT Data values defining smoothed curve which fits the Rhodata\
\>PHSXY.FIT Data values defining smoothed curve which fits the Phsdata

**Example:**

\>RHOYX ROT=RHOROT // 20

1.17042065E+01 1.11513662E+01 1.18186188E+01 1.15031490E+01
1.08769321E+01

1.04818220E+01 9.34318638E+00 8.43346500E+00 7.19581127E+00
6.51003361E+00

6.20709038E+00 5.71676922E+00 4.03001356E+00 7.23312092E+00
1.38045464E+01

7.60633039E+00 7.40507936E+00 5.60898781E+00 5.02285671E+00
1.28740139E+01

\>PHSYX ROT=RHOROT // 20

-1.33743698E+02 -1.32722519E+02 -1.30825089E+02 -1.29616257E+02
-1.32089432E+02

-1.28722198E+02 -1.25549049E+02 -1.24309563E+02 -1.22039192E+02
-1.22824020E+02

-1.23723236E+02 -1.19973267E+02 -1.39091095E+02 -1.35322647E+02
-1.22721138E+02

-1.03210579E+02 -1.18133347E+02 -1.22277962E+02 -1.14281380E+02
-1.18818275E+02

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT data section. They may not appear in an
\>=EMAPSECT data section. Any apparent resistivity blocks in the
sections must follow the \>FREQ block, any impedance blocks, and the
optional \>RHOROT block, if included. One or more of any or all may
appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

TYPE Confidence % for .ERR data or String or " " " "\
fitting method for .FIT data.

ROT Type of rotation applied "NONE", "NORTH",\
or "RHOROT" "NONE"

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

EX Meas ID for Ex measurement Def Meas ID or " " Dyn EX

EY Meas ID for Ey measurement Def Meas ID or " " Dyn EY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. If the ROT option is "RHOROT" then the apparent
resistivities are assumed to have been rotated to the angles indicated
in the \>RHOROT data block. If it is "NORTH", they are assumed to have
been rotated to true north. If it is "NONE", they are assumed to be in
the measurement directions. Only apparent resistivities computed from
tensor impedances (see note 2 below) may be rotated.

2\. The dynamic defaults for HX, HY, EX, EY, RX, and RY were set by the
\>=MTSECT, \>=EMAPSECT, or \>=OTHERSECT block. If any were not
specified, the corresponding dynamic default was set to " ". All of
these options (after application of dynamic defaults) may be " ",
indicating no measurement. Although no restrictions are enforced, all
appropriate measurements should be defined. For each apparent
resistivity computed from a scalar impedance only one E and one H are
required (e.g. Ey and Hx for RHOYX). For rotatable apparent
resistivities two E's and two H's are required. If least-squares
estimation was used for the impedances, the reference measurements Rx
and Ry must be indicated. This is true whether they are coincident with
other measurements (local reference) or distinct (remote reference).

3\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

4\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. For MT data, it is recommended that rho's be delivered
rotated to maximize one of the criteria described in Section 5.8. In
this case, this rotation angle must be specified in a \>RHOROT block
which must appear previously. For EMAP data, it is recommended that
rho's be delivered in measurement directions.

2\. Generally the HX, HY, EX, EY, RX, RY, and NFREQ options will be
provided by the \>=MTSECT or \>=EMAPSECT block through the dynamic
default mechanism.

3\. The \>RHOYX.ERR block gives the size (in decades) of the error bars
representing +/- one standard deviation of log10(rho). This error bar is
symmetrical in log10(rho) space.

4\. The \>RHOYX.FIT block may be optionally included to specify a smooth
or interpreted curve to be associated with the raw data.

5\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors.

##  14.4 \>RHOYY, \>PHSYY, \>RHOYY.VAR, \>PHSYY.VAR \>RHOYY.ERR, \>PHSYY.ERR, \>RHOYY.FIT, \>PHSYY.FIT

**Description:** \>RHOYY Magnitude of apparent resistivity (W-m)
computed from Z\
\>PHSYY Phase angle of apparent resistivity (deg) computed from Z\
\>RHOYY.VAR Variance of Rhocomputed from variances of real and imag
parts of Z\
\>PHSYY.VAR Variance of Phscomputed from variances of real and imag
parts of\
\>RHOYY.ERR Logerror bar (in decades) assoc. with Rho\
\>PHSYY.ERR Error bar (in degrees) assoc. with Phs\
\>RHOYY.FIT Data values defining smoothed curve which fits the Rhodata\
\>PHSYY.FIT Data values defining smoothed curve which fits the Phsdata

**Example:**

\>RHOYY ROT=RHOROT // 20

1.17042065E+01 1.11513662E+01 1.18186188E+01 1.15031490E+01
1.08769321E+01

1.04818220E+01 9.34318638E+00 8.43346500E+00 7.19581127E+00
6.51003361E+00

6.20709038E+00 5.71676922E+00 4.03001356E+00 7.23312092E+00
1.38045464E+01

7.60633039E+00 7.40507936E+00 5.60898781E+00 5.02285671E+00
1.28740139E+01

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT data section. They may not appear in an
\>=EMAPSECT data section. Any apparent resistivity blocks in the
sections must follow the \>FREQ block, any impedance blocks, and the
optional \>RHOROT block, if included. One or more of any or all may
appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

TYPE Confidence % for.ERR data or String or " " " "\
fitting method for .FIT data.

ROT Type of rotation applied "NONE", "NORTH",\
or "RHOROT" "NONE"

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

EX Meas ID for Ex measurement Def Meas ID or " " Dyn EX

EY Meas ID for Ey measurement Def Meas ID or " " Dyn EY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. If the ROT option is "RHOROT" then the apparent
resistivities are assumed to have been rotated to the angles indicated
in the \>RHOROT data block. If it is "NORTH", they are assumed to have
been rotated to true north. If it is "NONE", they are assumed to be in
the measurement directions. Only apparent resistivities computed from
tensor impedances (see note 2 below) may be rotated.

2\. The dynamic defaults for HX, HY, EX, EY, RX, and RY were set by the
\>=MTSECT, \>=EMAPSECT, or \>=OTHERSECT block. If any were not
specified, the corresponding dynamic default was set to " ". All of
these options (after application of dynamic defaults) may be " ",
indicating no measurement. Although no restrictions are enforced, all
appropriate measurements should be defined. For each apparent
resistivity computed from a scalar impedance only one E and one H are
required (e.g. Ey and Hy for RHOYY). For rotatable apparent
resistivities two E's and two H's are required. If least-squares
estimation was used for the impedances, the reference measurements Rx
and Ry must be indicated. This is true whether they are coincident with
other measurements (local reference) or distinct (remote reference).

3\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

4\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. For MT data, it is recommended that rho's be delivered
rotated to maximize one of the criteria described in Section 5.8. In
this case, this rotation angle must be specified in a \>RHOROT block
which must appear previously. For EMAP data, it is recommended that
rho's be delivered in measurement directions.

2\. Generally the HX, HY, EX, EY, RX, RY, and NFREQ options will be
provided by the \>=MTSECT or \>=EMAPSECT block through the dynamic
default mechanism.

3\. The \>RHOYY.ERR block gives the size (in decades) of the error bars
representing +/- one standard deviation of log10(rho). This error bar is
symmetrical in log10(rho) space.

4\. The \>RHOYY.FIT block may be optionally included to specify a smooth
or interpreted curve to be associated with the raw data.

5\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors

##  14.5 \>FRHOXX, \>FPHSXX, \>FRHOXX.FIT, \>FPHSXX.FIT, \>FRHOXY, \>FPHSXY, \>FRHOXY.FIT, \>FPHSXY.FIT

**Description:** \>FRHOXX Apparent resistivity (W-m) comp. from
spatially filtered Z\
\>FPHSXX Phase (deg) computed from spatially filtered Z\
\>FRHOXX.FIT Data defining smoothed curve which fits the filtered Rho\
\>FPHSXX.FIT Data defining smoothed curve which fits the filtered Phs\
\>FRHOXY Apparent resistivity (W-m) comp. from filtered Z\
\>FPHSXY Phase (deg) computed from filtered Z\
\>FRHOXY.FIT Data defining smoothed curve which fits the filtered
Rhodata\
\>FPHSXY.FIT Data defining smoothed curve which fits the filtered Phs

**Example:**

\>FRHOXY ROT=RHOROT // 20

1.08579102E+01 1.09430246E+01 1.05040903E+01 1.13740978E+01
1.04564753E+01

1.09703875E+01 1.08448954E+01 1.03996630E+01 9.13816547E+00
8.84461498E+00

8.36482430E+00 8.65559006E+00 9.26512432E+00 6.76110649E+00
1.29676619E+01

1.17602291E+01 1.24114132E+01 2.58277512E+01 1.86857986E+01
1.18354082E+01

\>FPHSXY ROT=RHOROT // 20

4.44184723E+01 4.45486832E+01 4.41194191E+01 4.45983124E+01
4.38439178E+01

4.55155830E+01 4.85306206E+01 5.13925629E+01 5.37120476E+01
5.23208351E+01

4.66266098E+01 5.19162025E+01 6.89909592E+01 2.81978683E+01
2.63625183E+01

3.30418930E+01 3.11888943E+01 4.74999847E+01 5.26897507E+01
2.37417355E+01

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=EMAP data section. They may not appear in an \>=MTSECT
data section. Any apparent resistivity blocks in the sections must
follow the \>FREQ block, and any impedance blocks. One or more of any or
all may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

TYPE Fitting method for .FIT data String or " " " "

ROT Type of rotation applied "NONE", "NORTH",\
or "RHOROT" "NONE"

EX Meas ID for Ex measurement Defined Meas ID Required

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. The dynamic defaults for HX, HY, RX, and RY were set by
the \>=EMAPSECT, or \>=OTHERSECT block. If any were not specified, the
corresponding dynamic default was set to " ". All of these options
(after application of dynamic defaults) may be " ", indicating no
measurement. Although no restrictions are enforced, all appropriate
measurements should be defined. For each apparent resistivity one E and
one H are required (e.g. Ex and Hx for RHOXX, Ex and Hy for RHOXY). If
least-squares estimation was used, the reference measurements Rx and Ry
must be indicated. This is true whether they are coincident with other
measurements (local reference) or distinct (remote reference).

2\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

3\. For apparent resistivities derived from EMAP filtered impedances,
the ROT option should be "NONE", indicating that the apparent
resistivities correspond to the measurement directions.

4, The CHKSUM option, if specified, may be used to detect errors in data
writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. For EMAP data, it is recommended that rho's be delivered
in measurement directions.

2\. Generally the HX, HY, EX, EY, RX, RY, and NFREQ options will be
provided by the \>=EMAPSECT block through the dynamic default mechanism.

3\. The .FIT blocks may be optionally included to specify a smooth or
interpreted curve to be associated with the raw data.

4\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors

#  15.0 Continuous 1-D Inversion Data Blocks

##  15.1 \>RES1DXX, \>DEP1DXX. RES1DXY, \>DEP1DXY

**Description:** \>RES1DXX True resistivity (W-m) computed from Rhousing
1-D continuous inverse\
\>DEP1DXX Depth (units) computed from Rhousing 1-D continuous inverse\
\>RES1DXY True resistivity (W-m) computed from Rhousing 1-D continuous
inverse\
\>DEP1DXY Depth (units) computed from Rhousing 1-D continuous inverse

**Example:**

\>RES1DXY ROT=RHOROT // 20

1.17015715E+01 1.32999439E+01 1.30004625E+01 1.19078741E+01
1.02527933E+01

9.63494396E+00 7.98624992E+00 6.89576387E+00 6.04798603E+00
6.33519840E+00

6.31925201E+00 6.30551910E+00 8.21470928E+00 1.22897148E+01
1.78367996E+01

3.04577389E+01 4.93220749E+01 6.53172836E+01 7.49221878E+01
7.50644455E+01

\>DEP1DXY ROT=RHOROT // 20

3.37705719E+02 3.98757294E+02 4.91241516E+02 5.76613159E+02
6.95680969E+02

7.99844788E+02 9.56142578E+02 1.07347095E+03 1.26384119E+03
1.40669055E+03

1.68963354E+03 1.89222839E+03 2.29579883E+03 2.69996313E+03
3.48682007E+03

4.27994043E+03 5.86284277E+03 7.42579736E+03 1.02798584E+04
1.28665928E+04

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT or \>=EMAPSECT data section. Any continuous 1-D
data blocks in these sections must follow the \>FREQ block, any
impedance blocks, and any apparent resistivity blocks. One or more of
any or all may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of freqs used for inversion Integer \>=1 Dyn NF

TYPE Type of inversion String or " " " "

ROT Type of rotation applied to Rho data "NONE", "NORTH",\
or "RHOROT" "NONE"

UNITS Units for depth "M" or "FT" "M"

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

EX Meas ID for Ex measurement Def Meas ID or " " Dyn EX

EY Meas ID for Ey measurement Def Meas ID or " " Dyn EY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values. There is
a one-to-one correspondence between a depth block and its corresponding
resistivity block. The values must be within the legal range for reals.
Depth values are relative to the surface and increase with depth. Thus,
they must be all greater than zero and strictly increasing. The special
value for empty (Section 6.23) should be used to denote missing data
values and the count should be set to zero (Section 6.23) if the data
set is empty.

**Notes:** 1. If the ROT option is "RHOROT" then the inversion is
assumed to have been computed from apparent resistivities which were
rotated to the angles indicated in the \>RHOROT data block. If it is
"NORTH", they are assumed to have been rotated to true north. If it is
"NONE", the apparent resistivities are assumed to be in the measurement
directions. Inversion of MT data in the measurement directions or
rotated to true north is usually of little interest, so ROT=RHOROT
should almost always specified for inversion data blocks in an \>=MTSECT
data section. Only apparent resistivities computed from tensor
impedances (see note 2 below) may be rotated.

2\. For inversions derived from EMAP impedances, the ROT option should
be "NONE", indicating that the impedances correspond to the measurement
directions.

3\. The dynamic defaults for HX, HY, EX, EY, RX, and RY were set by the
\>=MTSECT, \>=EMAPSECT, or \>=OTHERSECT block. If any were not
specified, the corresponding dynamic default was set to " ". All of
these options (after application of dynamic defaults) may be " ",
indicating no measurement. Although no restrictions are enforced, all
appropriate measurements should be defined. For each continuous
inversion derived from a scalar impedance only one E and one H are
required (e.g. Ex and Hx for RESXX and DEP1DXX, or Ex and Hy for RESXY
and DEP1DXY). For inversions computed from rotated apparent
resistivities two E's and two H's are required. If least-squares
estimation was used for the impedances, the reference measurements Rx
and Ry must be indicated. This is true whether they are coincident with
other measurements (local reference) or distinct (remote reference).

4\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

5\. The type of inversion used may be BOSTICK or another technique. If
applicable, the option should also indicate how the slope was derived
(e.g from amplitude differences or Hilbert transform of phase).

6\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. 1-D continuous inversions are derived from a rho data set.
For MT data, it is recommended that rho's be rotated to maximize one of
the criteria described in Section 5.8. In this case, this rotation angle
must be specified in a \>RHOROT block which must appear previously. For
EMAP data, it is recommended that rho's be in measurement directions.

2\. Generally the HX, HY, EX, EY, RX, RY, and NFREQ options for the rho
data from which the 1-D inverse was derived will be provided by the
\>=MTSECT or \>=EMAPSECT block through the dynamic default mechanism.

3\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors

##  15.2 \>RES1DYX, \>DEP1DYX, RES1DYY, \>DEP1DYY

**Description:** \>RES1DYX True resistivity (W-m) computed from Rhousing
1-D continuous inverse\
\>DEP1DYX Depth (units) computed from Rhousing 1-D continuous inverse\
\>RES1DYY True resistivity (W-m) computed from Rhousing 1-D continuous
inverse\
\>DEP1DYY Depth (units) computed from Rhousing 1-D continuous inverse

**Example:**

\>RES1DYX ROT=RHOROT // 20

9.14013386E+00 1.07764425E+01 1.23268681E+01 9.24939346E+00
8.64568615E+00

6.52991819E+00 4.99243736E+00 3.91825318E+00 3.63707042E+00
4.04100895E+00

5.38858700E+00 7.09615088E+00 8.23903465E+00 9.36382961E+00
1.00957212E+01

1.01091537E+01 9.00431824E+00 7.09470081E+00 6.01520729E+00
5.34585762E+00

\>DEP1DYX ROT=RHOROT // 20

3.43829926E+02 3.84529755E+02 4.88384460E+02 5.52063416E+02
6.72104675E+02

7.52524536E+02 8.82921448E+02 9.59777039E+02 1.10508777E+03
1.21033301E+03

1.44122864E+03 1.67296021E+03 2.08549585E+03 2.46865527E+03
3.11859448E+03

3.69985205E+03 4.63237549E+03 5.34728369E+03 6.42516455E+03
7.25676367E+03

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT data section. They may not appear in an
\>=EMAPSECT data section. Any continuous 1-D data blocks in these
sections must follow the \>FREQ block, any impedance blocks, and any
apparent resistivity blocks. One or more of any or all may appear
anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of freqs used for inversion Integer \>=1 Dyn NF

TYPE Type of inversion String or " " " "

ROT Type of rotation applied to Rho data "NONE", "NORTH",\
or "RHOROT" "NONE"

UNITS Units for depth "M" or "FT" "M"

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

EX Meas ID for Ex measurement Def Meas ID or " " Dyn EX

EY Meas ID for Ey measurement Def Meas ID or " " Dyn EY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values. There is
a one-to-one correspondence between a depth block and its corresponding
resistivity block. The values must be within the legal range for reals.
Depth values are relative to the surface and increase with depth. Thus,
they must be all greater than zero and strictly increasing. The special
value for empty (Section 6.23) should be used to denote missing data
values and the count should be set to zero (Section 6.23) if the data
set is empty.

**Notes:** 1. If the ROT option is "RHOROT" then the inversion is
assumed to have been computed from apparent resistivities which were
rotated to the angles indicated in the \>RHOROT data block. If it is
"NORTH", they are assumed to have been rotated to true north. If it is
"NONE", the apparent resistivities are assumed to be in the measurement
directions. Inversion of MT data in the measurement directions or
rotated to true north is usually of little interest, so ROT=RHOROT
should almost always specified for inversion data blocks in an \>=MTSECT
data section. Only apparent resistivities computed from tensor
impedances (see note 2 below) may be rotated.

2\. For inversions derived from EMAP impedances, the ROT option should
be "NONE", indicating that the impedances correspond to the measurement
directions.

3\. The dynamic defaults for HX, HY, EX, EY, RX, and RY were set by the
\>=MTSECT, \>=EMAPSECT, or \>=OTHERSECT block. If any were not
specified, the corresponding dynamic default was set to " ". All of
these options (after application of dynamic defaults) may be " ",
indicating no measurement. Although no restrictions are enforced, all
appropriate measurements should be defined. For each continuous
inversion derived from a scalar impedance only one E and one H are
required (e.g. Ey and Hx for RESYX and DEP1DYX, or Ey and Hy for RESYY
and DEP1DYY). For inversions computed from rotated apparent
resistivities two E's and two H's are required. If least-squares
estimation was used for the impedances, the reference measurements Rx
and Ry must be indicated. This is true whether they are coincident with
other measurements (local reference) or distinct (remote reference).

4\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

5\. The type of inversion used may be BOSTICK or another technique. If
applicable, the option should also indicate how the slope was derived
(e.g from amplitude differences or Hilbert transform of phase).

6\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. 1-D continuous inversions are derived from a rho data set.
For MT data, it is recommended that rho's be rotated to maximize one of
the criteria described in Section 5.8. In this case, this rotation angle
must be specified in a \>RHOROT block which must appear previously. For
EMAP data, it is recommended that rho's be in measurement directions.

2\. Generally the HX, HY, EX, EY, RX, RY, and NFREQ options for the rho
data from which the 1-D inverse was derived will be provided by the
\>=MTSECT or \>=EMAPSECT block through the dynamic default mechanism.

3\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors

##  15.3 \>FRES1DXX, \>FDEP1DXX, FRES1DXY, \>FDEP1DXY

**Description:** \>FRES1DXX True resistivity (W-m) computed using a 1-D
cont. inverse from apparent resistivity data derived from spatially
filtered Z data\
\>FDEP1DXX Depth (units) corresponding one-to-one with the FRES1DXX
resistivities\
\>FRES1DXY True resistivity (W-m) computed using a 1-D cont. inverse
from\
apparent resistivity data derived from spatially filtered Z data\
\>FDEP1DXY Depth (units) corresponding one-to-one with the FRES1DXY
resistivities

**Example:**

\>FRES1DXY ROT=RHOROT // 20

1.17015715E+01 1.32999439E+01 1.30004625E+01 1.19078741E+01
1.02527933E+01

9.63494396E+00 7.98624992E+00 6.89576387E+00 6.04798603E+00
6.33519840E+00

6.31925201E+00 6.30551910E+00 8.21470928E+00 1.22897148E+01
1.78367996E+01

3.04577389E+01 4.93220749E+01 6.53172836E+01 7.49221878E+01
7.50644455E+01

\>FDEP1DXY ROT=RHOROT // 20

3.37705719E+02 3.98757294E+02 4.91241516E+02 5.76613159E+02
6.95680969E+02

7.99844788E+02 9.56142578E+02 1.07347095E+03 1.26384119E+03
1.40669055E+03

1.68963354E+03 1.89222839E+03 2.29579883E+03 2.69996313E+03
3.48682007E+03

4.27994043E+03 5.86284277E+03 7.42579736E+03 1.02798584E+04
1.28665928E+04

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=EMAPSECT. They may not appear in an \>=MTSECT data
section. Any continuous 1-D data blocks in the sections must follow the
\>FREQ block, any impedance blocks, and any apparent resistivity blocks.
One or more of any or all may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of freqs used for inversion Integer \>=1 Dyn NF

TYPE Type of inversion String or " " " "

ROT Type of rotation applied to Rho data "NONE", "NORTH",\
or "RHOROT" "NONE"

UNITS Units for depth "M" or "FT" "M"

HX Meas ID for Hx measurement Def Meas ID or "" Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

EX Meas ID for Ex measurement Def Meas ID or " " Dyn EX

EY Meas ID for Ey measurement Def Meas ID or " " Dyn EY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values. There is
a one-to-one correspondence between a depth block and its corresponding
resistivity block. The values must be within the legal range for reals.
Depth values are relative to the surface and increase with depth. Thus,
they must be all greater than zero and strictly increasing. The special
value for empty (Section 6.23) should be used to denote missing data
values and the count should be set to zero (Section 6.23) if the data
set is empty.

**Notes:** 1. The dynamic defaults for HX, HY, EX, EY, RX, and RY were
set by the \>=MTSECT, \>=EMAPSECT, or \>=OTHERSECT block. If any were
not specified, the corresponding dynamic default was set to " ". All of
these options (after application of dynamic defaults) may be " ",
indicating no measurement. Although no restrictions are enforced, all
appropriate measurements should be defined. For each continuous
inversion derived from a scalar impedance one E and one H are required
(e.g. Ex and Hx for FRESXX and FDEPXX, or Ex and Hy for FRESXY and
FDEP1DXY). If least-squares estimation was used for the impedances, the
reference measurements Rx and Ry must be indicated. This is true whether
they are coincident with other measurements (local reference) or
distinct (remote reference).

2\. For inversions derived from EMAP filtered impedances, the ROT option
should be "NONE", indicating that the impedances correspond to the
measurement directions.

3\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

4\. The type of inversion used may be BOSTICK or another technique. If
applicable, the option should also indicate how the slope was derived
(e.g from amplitude differences or Hilbert transform of phase).

5\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hints:** 1. 1-D continuous inversions are derived from a rho data set.
For MT data, it is recommended that rho's be rotated to maximize one of
the criteria described in Section 5.8. In this case, this rotation angle
must be specified in a \>RHOROT block which must appear previously. For
EMAP data, it is recommended that rho's be in measurement directions.

2\. Generally the HX, HY, EX, EY, RX, RY, and NFREQ options for the rho
data from which the 1-D inverse was derived will be provided by the
\>=MTSECT or \>=EMAPSECT block through the dynamic default mechanism.

3\. The CHKSUM option, as defined, has proven to be unreliable because
of rounding errors

#  16.0 Coherency and Signal Data Blocks

##  16.1 \>COH

**Description:** Ordinary coherency between any two measurements as a
function of freq.

**Example:**

\>COH MEAS1=1011.101 MEAS2=1015.101 ROT=NORTH // 20

9.60033655E-01 9.72313225E-01 9.66603339E-01 9.59068954E-01
9.55812097E-01

9.49533224E-01 9.30146277E-01 9.02701676E-01 7.87032247E-01
7.49909878E-01

5.95737398E-01 4.28677410E-01 3.08223873E-01 5.21349132E-01
6.18800640E-01

6.26757741E-01 7.85922527E-01 5.30418575E-01 6.13066256E-01
6.97230458E-01

**Restrictions:** One or more instances of this data block can appear in
an \>=MTSECT data section, or an \>=EMAPSECT data section. Any coherency
data blocks in these sections must follow the \>FREQ block, any
impedance blocks, any apparent resistivity blocks, and any 1-D inversion
blocks. One or more may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of freqs used inversion Integer \>=1 Dyn NF

MEAS1 Meas ID for the 1st meas. Def Meas ID Required

MEAS2 Meas ID for the 2nd meas. Def Meas ID Required

ROT Rotation of measurements "NONE", "NORTH",\
or "RHOROT" "NONE"

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values. The
special value for empty (Section 6.23) should be used to denote missing
data values and the count should be set to zero (Section 6.23) if the
data set is empty.

**Notes:** 1. If coherencies are being used in identifying the source(s)
of noise in the data, it is most useful to have these parameters in the
direction of the measurements (ROT=NONE). For evaluating data quality it
is most useful to have these parameters in the direction of the apparent
resistivities (ROT=RHOROT or ROT=NORTH).

2\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

3\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hint:** Generally the NFREQ option will be provided by the \>=MTSECT
or \>=EMAPSECT block through the dynamic default mechanism.

##  16.2 \>EPREDCOH

**Description:** Multiple coherency relationship between an E
measurement, and a predicted E measurement derived from two H
measurements and a tensor impedance Z.

**Example:**

\>EPREDCOH MEAS1=1011.001 MEAS2=1012.001 EPRED=1014.001 ROT=NORTH // 20

9.34974968E-01 8.53829205E-01 9.41578388E-01 9.22673702E-01
9.20535862E-01

9.21728909E-01 9.01208401E-01 8.90061975E-01 7.63703167E-01
7.29590595E-01

5.30870974E-01 3.44830692E-01 2.02085733E-01 2.30681986E-01
4.38924909E-01

6.36722207E-01 7.63903916E-01 5.41088402E-01 4.80003685E-01
5.86532772E-01

**Restrictions:** One or more instances of this data block can appear in
an \>=MTSECT data section, or an \>=EMAPSECT data section. Any coherency
data blocks in these sections must follow the \>FREQ block, any
impedance blocks, any apparent resistivity blocks, and any 1-D inversion
blocks. One or more may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of freqs for inversion Integer \>=1 Dyn NF

MEAS1 Meas ID for the 1st H meas. Def Meas ID Required

MEAS2 Meas ID for the 2nd H meas. Def Meas ID Required

EPRED Meas ID for predicted E meas. Def Meas ID Required

ROT Orientation of measurements "NONE", "NORTH",\
or "RHOROT" "NONE"

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values. The
special value for empty (Section 6.23) should be used to denote missing
data values and the count should be set to zero (Section 6.23) if the
data set is empty.

**Notes:** 1. If coherencies are being used in identifying the source(s)
of noise in the data, it is most useful to have these parameters in the
direction of the measurements (ROT=NONE). For evaluating data quality it
is most useful to have these parameters in the direction of the apparent
resistivities (ROT=RHOROT or ROT=NORTH).

2\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

3\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hint:** Generally the NFREQ option will be provided by the \>=MTSECT
or \>=EMAPSECT block through the dynamic default mechanism.

##  16.3 \>HPREDCOH

**Description:** Multiple coherency relationship between an H
measurement, and a predicted H measurement derived from two E
measurements and a tensor admittance Y.

**Example:**

\>HPREDCOH MEAS1=1014.001 MEAS2=1015.001 HPRED=1011.001 ROT=NORTH // 20

9.60707903E-01 9.75124002E-01 9.66981709E-01 9.60868239E-01
9.57774282E-01

9.52683330E-01 9.39414024E-01 9.17613506E-01 8.33122373E-01
7.89471686E-01

6.43265784E-01 4.61068988E-01 3.09651703E-01 5.41831315E-01
6.20322108E-01

6.84999466E-01 7.98119485E-01 5.46519339E-01 6.25260115E-01
7.96124279E-01

**Restrictions:** One or more instances of this data block can appear in
an \>=MTSECT data section, or an \>=EMAPSECT data section. Any coherency
data blocks in these sections must follow the \>FREQ block, any
impedance blocks, any apparent resistivity blocks, and any 1-D inversion
blocks. One or more may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of freqs for inversion Integer \>=1 Dyn NF

MEAS1 Meas ID for the 1st E meas. Def Meas ID Required

MEAS2 Meas ID for the 2nd E meas. Def Meas ID Required

HPRED Meas ID for predicted H meas. Def Meas ID Required

ROT Orientation of measurements "NONE", "NORTH",\
or "RHOROT" "NONE"

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values. The
special value for empty (Section 6.23) should be used to denote missing
data values and the count should be set to zero (Section 6.23) if the
data set is empty.

**Notes:** 1. If coherencies are being used in identifying the source(s)
of noise in the data, it is most useful to have these parameters in the
direction of the measurements (ROT=NONE). For evaluating data quality it
is most useful to have these parameters in the direction of the apparent
resistivities (ROT=RHOROT or ROT=NORTH).

2\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

3\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hint:** Generally the NFREQ option will be provided by the \>=MTSECT
or \>=EMAPSECT block through the dynamic default mechanism.

##  16.4 \>SIGAMP

**Description:** Signal amplitude (or power) spectra for a measurement
as a function of frequency.

**Example:**

\>SIGAMP MEAS=1012.001 ROT=NORTH // 20

1.92698289E-03 1.83258369E-03 1.74875022E-03 1.55375735E-03
1.58419774E-03

1.70137570E-03 1.95880537E-03 2.05492927E-03 2.16831383E-03
2.20897049E-03

2.01171148E-03 2.24006665E-03 2.48103053E-03 2.50982610E-03
3.42130358E-03

1.38269709E-02 1.86840594E-02 1.62400678E-02 2.61241812E-02
2.74835080E-02

**Restrictions:** One or more instances of this data block can appear in
an \>=MTSECT data section, or an \>=EMAPSECT data section. Any signal
data blocks in these sections must follow the \>FREQ block, any
impedance blocks, any apparent resistivity blocks, and any 1-D inversion
blocks. One or more may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of freqs for inversion Integer \>=1 Dyn NF

MEAS Meas ID for the measurement. Def Meas ID Required

AMPPWR Whether spectra is amp or power "AMP" or "PWR" "AMP"

EUNITS Units for E spectra (amplitude). "MV/KM" or "V/M" "MV/KM"

HUNITS Units for H spectra (amplitude) "NT" "NT"

ROT Orientation of measurements "NONE", "NORTH",\
or "RHOROT" "NONE"

TYPE Total field, est. signal, or est. noise "FIELD", "SIGNAL",\
or "NOISE" "FIELD"

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values. The
special value for empty (Section 6.23) should be used to denote missing
data values and the count should be set to zero (Section 6.23) if the
data set is empty.

**Notes:** 1. Either the EUNITS option or the HUNITS option, as
appropriate for the measurement, may be specified for documentation
purposes, or if E spectra are not in default units. If the AMPPWR option
is PWR, then the units are the squares of the amplitude units.

2\. If signal amplitude (or power spectral density) is being used in
identifying the source(s) of noise in the data, it is most useful to
have these parameters in the direction of the measurements (ROT=NONE).
For evaluating data quality it is most useful to have these parameters
in the direction of the apparent resistivities (ROT=RHOROT or
ROT=NORTH).

3\. The signal amplitude (or power spectral density) can either be
calculated from the total field (TYPE=FIELD), from the estimated signal
only (TYPE=SIGNAL), or from the estimated noise only (TYPE=NOISE). The
estimated signal and noise can be computed using a remote reference
(Gamble, 1978).

4\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

5\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hint:** Generally the NFREQ option will be provided by the \>=MTSECT
or \>=EMAPSECT block through the dynamic default mechanism.

##  16.5 \>SIGNOISE

**Description:** Signal-to-noise ratio for a measurement as a function
of frequency.

**Example:**

\>SIGNOISE MEAS=1011.001 ROT=NORTH // 20

9.63047802E-01 9.83598828E-01 9.88982439E-01 9.92118776E-01
9.87905025E-01

9.89448309E-01 9.90553796E-01 9.87476230E-01 9.82665181E-01
9.80461240E-01

9.35843825E-01 9.11659241E-01 1.00718665E+00 8.27387989E-01
8.91560793E-01

9.85390067E-01 9.93908286E-01 9.94895220E-01 8.03094149E-01
9.87491071E-01

**Restrictions:** One or more instances of this data block can appear in
an \>=MTSECT data section, or an \>=EMAPSECT data section. Any signal
data blocks in these sections must follow the \>FREQ block, any
impedance blocks, any apparent resistivity blocks, and any 1-D inversion
blocks. One or more may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of freqs for inversion Integer \>=1 Dyn NF

MEAS Meas ID for the measurement. Def Meas ID Required

ROT Orientation of measurements "NONE", "NORTH",\
or "RHOROT" "NONE"

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values. All data
values must be \>=0 and \<=1. The special value for empty (Section 6.23)
should be used to denote missing data values and the count should be set
to zero (Section 6.23) if the data set is empty.

**Notes:** 1. The estimated signal and noise can be computed using a
remote reference (Gamble, 1978). From these, signal/(signal+noise) can
be computed.

2\. If signal amplitude (or power spectral density) is being used in
identifying the source(s) of noise in the data, it is most useful to
have these parameters in the direction of the measurements (ROT=NONE).
For evaluating data quality it is most useful to have these parameters
in the direction of the apparent resistivities (ROT=RHOROT or
ROT=NORTH).

3\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

4\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hint:** Generally the NFREQ option will be provided by the \>=MTSECT
or \>=EMAPSECT block through the dynamic default mechanism.

#  17.0 Tipper Data Blocks

##  17.1 \>TIPMAG, \>TIPPHS, \>TIPMAG.ERR, \>TIPPHS.ERR, \>TIPMAG.FIT, \>TIPPHS.FIT

**Description:** \>TIPMAG Magnitude of total tipper\
\>TIPPHS Phase angle of total tipper\
\>TIPMAG.VAR Variance of Tipper magnitude\
\>TIPPHS.VAR Variance of Tipper phase\
\>TIPMAG.ERR Error bar assoc. with TIPMAG\
\>TIPPHS.ERR Error bar (in degrees) assoc. with TIPPHS\
\>TIPMAGFIT Data values defining smoothed curve which fits the TIPMAG
data\
\>TIPPHS.FIT Data values defining smoothed curve which fits the TIPPHS
data

**Example:**

\>TIPMAG // 20

3.44053991E-02 2.77741961E-02 1.57841984E-02 1.58313140E-02
1.29138678E-02

2.00289786E-02 2.53893416E-02 3.00401263E-02 1.78977810E-02
6.76133260E-02

8.58623311E-02 6.44834638E-01 3.79827708E-01 2.41298199E-01
1.22498584E+00

1.08001776E-01 7.38304779E-02 1.37485325E-01 2.12266326E-01
2.85834283E-01

\>TIPPHS // 20

4.28428040E+01 3.32755089E+01 4.26912880E+01 1.10915861E+01
1.09842672E+01

1.32586594E+01 1.12150545E+01 4.03483810E+01 9.63721161E+01
8.86814423E+01

1.10555733E+02 1.10969086E+02 -5.10283546E+01 -6.45015945E+01
-3.42821960E+01

-1.12413170E+02 7.66205835E+00 1.56070114E+02 4.22109604E+01
9.70897522E+01

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT data section. They may not appear in an
\>=EMAPSECT data section. Any tipper blocks in the section must follow
the \>FREQ block, any impedance blocks, any apparent resistivity blocks,
and any 1-D inversion blocks. One or more of any or all may appear
anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

TYPE Confidence % for .ERR data or String or " " " "\
fitting method for .FIT data.

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

HZ Meas ID for Hz measurement Def Meas ID or " " Dyn EX

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. The dynamic defaults for HX, HY, HZ, RX, and RY were set
by the \>=MTSECT or \>=OTHERSECT block. If any were not specified, the
corresponding dynamic default was set to " ". All of these options
(after application of dynamic defaults) may be " ", indicating no
measurement. Although no restrictions are enforced, all appropriate
measurements should be defined. For the total tipper, HX, HY, and HZ are
required. If least-squares estimation was used for the tipper, the
reference measurements Rx and Ry must be indicated. This is true whether
they are coincident with other measurements (local reference) or
distinct (remote reference).

2\. The dynamic default for NF was set by the NFREQ option in the first
block of the section.

3\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hint:** Generally the HX, HY, HZ, RX, RY, and NFREQ options will be
provided by the \>=MTSECT or \>=EMAPSECT block through the dynamic
default mechanism.

#  18.0 Strike, Skew, and Ellipticity Data Blocks

##  18.1 \>ZSTRIKE, \>ZSKEW, \>.ZELLIP

**Description:** \>ZSTRIKE Impedance strike angle computed from the
impedance tensor Z\
\>ZSKEW Impedance skew computed from the impedance tensor Z\
\>ZELLIP Impedance ellipticity computed from the impedance tensor Z

**Example:**

\>ZSTRIKE // 20

5.52469330E+01 3.19378510E+01 3.35147095E+01 2.08763542E+01
2.56520157E+01

2.55614872E+01 2.84206772E+01 2.77896080E+01 2.73173637E+01
3.21205826E+01

4.17980728E+01 2.89566040E+01 1.29837198E+01 4.01946144E+01
1.35549011E+01

2.69927807E+01 1.16522007E+01 2.39066010E+01 2.88325691E+01
-2.70986767E+01

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT data section. They may not appear in an
\>=EMAPSECT data section. Any strike, skew, or ellipticity blocks in the
section must follow the \>FREQ block, any impedance blocks, any apparent
resistivity blocks, and any 1-D inversion blocks. One or more of any or
all may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

TYPE For ZSTRIKE, criteria for String or " " " "\
determining strike angle

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

EX Meas ID for Ex measurement Def Meas ID or " " Dyn EX

EY Meas ID for Ey measurement Def Meas ID or " " Dyn EY

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. The dynamic defaults for HX, HY, EX, EY, RX, and RY were
set by the \>=MTSECT or \>=OTHERSECT block. If any were not specified,
the corresponding dynamic default was set to " ". All of these options
(after application of dynamic defaults) may be " ", indicating no
measurement. Although no restrictions are enforced, all appropriate
measurements should be defined. For tensor impedances, two E's and two
H's are required. If least-squares estimation was used, the reference
measurements Rx and Ry must be indicated. This is true whether they are
coincident with other measurements (local reference) or distinct (remote
reference).

2\. The dynamic default for NF was set by the NFREQ option in the
section head block.

3\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hint:** Generally the HX, HY, EX, EY, RX, RY, and NFREQ options will
be provided by the \>=MTSECT or \>=EMAPSECT block through the dynamic
default mechanism.

##  18.2 \>TSTRIKE, \>TSKEW, \>TELLIP

**Description:** \>TSTRIKE Tipper strike angle computed from the tipper
tensor T\
\>TSKEW Tipper skew computed from the tipper tensor T\
\>TELLIP Tipper ellipticity computed from the tipper tensor T

**Example:**

\>TSTRIKE // 20

-1.36445892E+02 -1.40237686E+02 -1.67916595E+02 1.56392731E+02
1.45596680E+02

1.54393463E+02 -1.61574371E+02 -1.75743118E+02 1.58962204E+02
-1.52523285E+02

1.65875214E+02 1.57556396E+02 -1.11872910E+02 1.92892666E+01
7.56694870E+01

5.56710930E+01 6.83958511E+01 4.75166893E+01 9.93813171E+01
1.33683578E+02

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT data section. They may not appear in an
\>=EMAPSECT data section. Any strike, skew, or ellipticity blocks in the
section must follow the \>FREQ block, any impedance blocks, any apparent
resistivity blocks, and any 1-D inversion blocks. One or more of any or
all may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

TYPE For TSTRIKE, criteria for String or " " " "\
determining strike angle

HX Meas ID for Hx measurement Def Meas ID or " " Dyn HX

HY Meas ID for Hy measurement Def Meas ID or " " Dyn HY

HZ Meas ID for Hz measurement Def Meas ID or " " Dyn HX

RX Meas ID for Rx ref measurement Def Meas ID or " " Dyn RX

RY Meas ID for Ry ref measurement Def Meas ID or " " Dyn RY

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. The dynamic defaults for HX, HY, HZ, RX, and RY were set
by the \>=MTSECT or \>=OTHERSECT block. If any were not specified, the
corresponding dynamic default was set to " ". All of these options
(after application of dynamic defaults) may be " ", indicating no
measurement. Although no restrictions are enforced, all appropriate
measurements should be defined. For a tipper, Hx, Hy, and Hz are
required. If least-squares estimation was used, the reference
measurements Rx and Ry must be indicated. This is true whether they are
coincident with other measurements (local reference) or distinct (remote
reference).

2\. The dynamic default for NF was set by the NFREQ option in the
section head block.

3\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hint:** Generally the HX, HY, HZ, RX, RY, and NFREQ options will be
provided by the \>=MTSECT or \>=EMAPSECT block through the dynamic
default mechanism.

#  19.0 Spatial Filter Blocks

##  19.1 \>FILWIDTH, FILANGLE, EQUIVLEN

**Description:** \>FILWID Length of spatial filter in meters (or feet if
UNITS=FT)\
\>FILANGLE Angle of spatial filter in degrees (relative to true north)\
\>EQUIVLEN Length of spatial filter in equivalent dipole lengths

**Example:**

\>FILWIDTH //25\
-2.347654E+01 2.941484E+02 4.387478E+02 7.347589E+02 8.547757E+02
9.374453E+02\
-1.545830E+03 2.957935E+03 2.996078E+03 4.247589E+03 5.576574E+03
7.347774E+03\
-8.398290E+03 9.984084E+03 1.963377E+04 2.347776E+04 2.576756E+04
3.547445E+04\
-3.654398E+04 3.947066E+04 4.347478E+04 5.046567E+04 5.787054E+04
6.347487E+04\
-6.455098E+04

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=EMAP data section. They may not appear in an \>=MTSECT
data section. Any spatial filter width blocks in the section must follow
the \>FREQ block, any impedance blocks, any apparent resistivity blocks,
and any 1-D inversion blocks. One or more of any or all may appear
anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

NFREQ Number of frequencies Integer \>=1 Dyn NF

UNITS Units for filter/dipole lengths "M" or "FT" "M"

DIPLEN Dipole lengths for EQUIVLEN Number \>0 or " " " "

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set must contain exactly NFREQ data values
corresponding to the frequencies defined by the \>FREQ block. The values
must be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. The dynamic default for NF was set by the NFREQ option in
the section head block.

2\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

**Hint:** Generally the NFREQ option will be provided by the \>=EMAPSECT
block through the dynamic default mechanism.

#  20.0 Non-Standard Data Blocks

**Description:** \>\_\_\_\_.EXP Data of a type not specified by this
standard

**Example:**

\>RHOLAT1.EXP ROT=RHOROT // 20

1.08579102E+01 1.09430246E+01 1.05040903E+01 1.13740978E+01
1.04564753E+01

1.09703875E+01 1.08448954E+01 1.03996630E+01 9.13816547E+00
8.84461498E+00

8.36482430E+00 8.65559006E+00 9.26512432E+00 6.76110649E+00
1.29676619E+01

1.17602291E+01 1.24114132E+01 2.58277512E+01 1.86857986E+01
1.18354082E+01

**Restrictions:** One instance of any or all of these data blocks can
appear in an \>=MTSECT data section or an \>=EMAPSECT data section. Any
.EXP blocks in the sections must follow the \>FREQ block, any impedance
blocks, any apparent resistivity blocks, and any 1-D inversion blocks.
One or more of any or all may appear anywhere in \>=OTHERSECT sections.

[Option Name]{.underline} [Description]{.underline}
[Restrictions]{.underline} [Default]{.underline}

String \[1-16\] Any desired option String or " " " "

CHKSUM Checksum total for data values Number or " " " "

**Data Set:** Data set may contain any number of values. The values must
be within the legal range for reals. The special value for empty
(Section 6.23) should be used to denote missing data values and the
count should be set to zero (Section 6.23) if the data set is empty.

**Notes:** 1. The use of .EXP data blocks require the consent of all
parties. The definition of the data, the options, and the defaults for
.EXP blocks should be in the \>INFO text.

2\. The CHKSUM option, if specified, may be used to detect errors in
data writing, reading, or transmission. The value of the checksum is the
exact sum of all of the data values in the block. For purposes of
summing, the values represented by the output format are to be used.
Empty values (Section 6.23) are summed as zeroes. Blocks with binary
data sets may use the CHKSUM option. Because of the limits in formatting
real numbers, care should be exercised in writing and testing checksums.

#  21.0 Future Extensions

The \>OTHERSECT data section and the .EXP data blocks are intended to
provide flexibility to handle cases not covered by this standard for
limited applications or in an interim role. As new techniques and data
types come into use, the standard should be revised to reflect these.

# Appendix 1 - Terms and Definitions

**ASCII Data Set**

An ASCII data set consists of the character sequence "//", followed by a
count, followed by zero or more data values. The count and the data
values are represented by data values. See section 6.23, Data Set, and
Data Value.

**Backus-Naur Form (BNF)**

Backus-Naur form, or BNF, is a formal notation for precise syntax
specification used in this standard. See section 6.1 for a description
of the notation. It is described in detail by Aho and Ullman (1978). See
section 6.1.

**Binary Data Set**

A binary data set is a special kind of data set for use with very large
data sets where data compression is required. Binary data values are
placed in a parallel binary file and are referenced by the EDI
interchange file. When one of three special character sequences: "/I/",
"/R/", or "/D/" (for Integer, Real, and Double-precision Real data
respectively) is encountered, data is read from the binary data file.
See section 6.23.

**Channel**

A channel refers to a particular sensor setup. For electric field
channels, it is represented by a pair of X,Y, and Z offsets from the
reference location, one for each electrode. For magnetic field channels
it is represented by an X, Y, Z offset of the sensor from the reference
location, and azimuth and dip angles of the sensor. See Measurement ID.

**Comment**

Comments may be freely embedded within an EDI file any place where a
space can be except within a data set. A comment begins with the two
characters \>! and continues until another ! character is encountered.
See section 6.25.

**Data Block (or block)**

Data blocks are the basic building blocks from which EDI files are
constructed. Each consists of a keyword followed by an option list and a
data set. The keyword is required, but the option list and the data set
may or may not be present, depending on the keyword. A mechanism has
been included for including non-standard data blocks. See section 7.1
and EXP. Data Block.

**Data Set**

A data set is a series of values. There are two kinds of data sets:
ASCII data sets and binary data sets. A data set is indicated by "//"
(ASCII), "/I/" (Binary integer), "/R/" (Binary real), or "/D/" (Binary
double). If it is an ASCII data set it is followed by a count and zero
or more data values. If it is a binary data set, the count and data
values are read from a parallel binary file. See section 6.23, ASCII
Data Set, and Binary Data Set.

**Data Section**

A data section is a group of contiguous blocks which are related. All
data sections begin with a block whose keyword begins with \>=. All EDI
files must contain a \>=DEFMEAS data section which defines the
measurements used by the file. They may then contain one or more of the
following optional data sections: \>=TSERIESSECT, \>=SPECTRASECT,
\>=MTSECT, \>EMAPSECT, or \>=OTHERSECT. Any of these optional sections
can be processed independently of the others. See section 7.5.

**Data Value**

A data value is a single number in an ASCII data set. It is a set of
ASCII characters which represent a valid number. It may be an integer,
real, or floating point format. An empty data value is represented by a
special value defined by the EMPTY option in the \>HEAD block. See
section 6.22, ASCII Data Set, and Empty Data Value.

**Date**

The correct syntactic form for a date is MM/DD/YY, where MM is the month
01 to 12, DD is the day 01 to 31, and YY is the last two digits of the
year, 00 to 99. See section 6.22.

**Dynamic Option Default**

Some options have default values which depend upon previously set
values. The first block in a new section can define the dynamic defaults
for some options. Then, any data block within the section can use the
default value by not specifying that option or may specify a different
value by specifying the option. There are nine defined dynamic defaults:
HX, HY, HZ, EX, EY, RX, RY, NF, and NC. When writing an option list, if
the option value = default value, the option does not have to be
written. When reading, the default value should be filled in if the
option is not specified. See also section 6.24., and Option.

**Electrical Data Interchange (or EDI) File**

An ASCII data file whose format corresponds to the syntactic and
semantic specifications set forth in this standard.

**EMAP**

An acronym for Electro-Magnetic Array Profiling, a recently developed
geophysical exploration technique (Bostick, 1986), which uses magnetic
field measurements and an array of contiguous electric field
measurements to estimate the subsurface resistivity structure. See
section 7.54.

**EMAP Data Section**

An EMAP data section is a group of data blocks in an EDI file which
corresponds to an EMAP line, or a section of an EMAP line. It must begin
with an \>=EMAPSECT data block which lists the measurements used for the
EMAP processing. Following are data blocks for frequencies, impedances
(Z's), apparent resistivities (Rho's), one-dimensional continuous
inversions, coherencies, signal parameters, and other data blocks. See
section 7.54.

**Empty Data Set**

A data set (either ASCII or binary) is a count followed by a series of
data values. When a data set is completely empty, the count should be
set to zero, and no data presented. The use of a special representation
is in lieu of filling the data set with some arbitrary data value such
as zero or 9E99 to represent no data. See section 6.23 and Data Set.

**Empty Data Value**

When one or more, but not all (see Empty Data Set), of the values in a
data set unknown, a special "empty value" is used to represent those
values. The use of this special representation is in lieu of filling the
data value with some arbitrary number such as zero or 9E99. The empty
value is defined by the EMPTY option in the \>HEAD block. The static
default for the EMPTY option is 1.0E32. See section 6.23 and Data Value.

**End Block**

This data block has no option list and no data set. There is always
exactly one in each EDI file and it is always the last block in the
file.

**EXP Data Block**

A special mechanism has been included within this standard for handling
data blocks within an EDI file other than those currently defined by the
standard. This may be used to handle new types of data until they can be
officially added to the standard, or may be used for conveying special
data types. Encountering a data block with any keyword not included in
the standard is normally considered to be an error. However, if the
keyword ends with the extension ".EXP" the data block is considered to
be EXPerimental or an EXcePtion. In this case it must be a syntactically
correct data block, but no restrictions are enforced on its option list
or data set. Any use of EXP data blocks should be by agreement of
effected parties and should be documented in the \>INFO section. See
section 20.0

**Head Block**

The head block is always the first block in an EDI file. There is
exactly one head block per file. It has an option list but no data set.
Options describe when, where, and by whom the data was collected as well
as when, where, and by whom the EDI file was written.

**Integer**

Integers are considered to be two's compliment 16 bit quantities. The
range of integers is -32768 to 32767. See section 6.22, section 6.23,
Binary Data Set.

**Interchange Media**

This standard addresses the interchange media on which an EDI file
resides as a separate issue from the format of an EDI file. The only
standardized media are 9 track 1/2\" magnetic tape and IBM 3480
compatible tape cartridges, but any media acceptable to all concerned
parties may be used for the interchange of EDI files. Only 1600 BPI 9
track tape is acceptable for archival purposes. See sections 4.1 and
4.2.

**Keyword**

All data block begin with a keyword. Keywords begin with the character
"\>". The current standard defines 119 keywords. Additionally, the .EXP
extension allows non-standard keywords to be used within an EDI file.
New keywords may be added to the standard in the future as required. See
section 7.1, Data Block, EXP Data Block.

**Info Block**

The info block is the second block in an EDI file, immediately following
the head block. There is exactly one info block per file. The info block
has an option list with one option and no data set. Following the info
block is text which continues until another keyword is encountered. This
is a repository for important field comments, descriptions of data
acquisition and processing, data quality tables, and any other relevant
information.

**Measurement**

A measurement combines a channel and a run to uniquely identify a
particular set of data. The definition of a measurement includes a
complete description of the sensor location(s) and configuration, sensor
ID, filters, gain, acquisition channel, etc. All measurements must be
defined in the Define Measurement section. It may then be uniquely
referred to by its measurement ID. See Channel, Run, Measurement ID.

**Measurement ID (or ID)**

A number which uniquely identifies one of the measurements defined in
the Define Measurements section. Measurement IDs incorporate both
channel number and run number. The integer part is the channel number.
There may be a fractional part which gives the run number. The run
number for the first run is always 0. Thus, there is no fractional part
in the measurement ID's for the first (and often only) run in the file.
The number of digits in the fractional part is 2, 3, or 4, depending on
the value of the MAXRUN option in the \>=DEFINEMEAS data block. If the
value is 0 (default), then all measurement IDs are simply the channel
number. If the MAXRUN \<100, then all measurement IDs are chan num+(run
num/100). If MAXRUN is \>=100 and \<1000 then all measurement IDs are
chan num+(run num/1000). Finally, if MAXRUN is \>=1000, then measurement
IDs are chan num+(run num/10,000).

**Magnetotellurics (or MT)**

Magnetotellurics, or MT, is a geophysical exploration technique which
uses relationship between the earth's electric and magnetic fields as
measured at the surface to estimate the subsurface resistivity
structure.

**MT Data Section**

An MT data section is a set of contiguous data blocks associated with an
MT sounding. It always begins with a \>=MTSECT data block which defines
the measurements associated with the sounding. Following this may be
data blocks for frequencies, impedances (Z's), apparent resistivities
(Rho's), one-dimensional continuous inversions, coherencies, signal
parameters, and other data blocks. See section 7.53.

**Option**

An option is an option name, followed by the character "=", followed by
an option argument. It is the component from which option lists are
built. The type of the option is indicated by its option name. See
section 6.24, Option Argument, Option List, Option Name, Dynamic Option
Default, and Static Option Default.

**Option Argument**

An option argument is a string of 1 to 16 characters. Depending upon the
option name, there may be syntactic or semantic restrictions on the
option argument. Possible restrictions include valid measurement ID,
valid date, valid latitude, valid longitude, integer \>=0, integer \>=1,
number \>0, number \>=0, etc. These are given in the option tables in
sections 8-20. See section 6.24, Option, Option List, Option Name,
Dynamic Option Default, and Static Option Default.

**Option List**

An option list is a set of 0 or more options. They may appear only in
data blocks. For a given data block type, there is a list of allowable
options. Some are required, and some have default values and may be
omitted. These are given in the option tables in sections 8-20. See
section 6.24, option, Option Argument, Option Name, Dynamic Option
Default, and Static Option Default.

**Option Name**

An option name consists of 1 to 16 characters. Option names define the
type of an option just as keywords define the type of a data block. They
are defined by the standard in the same way as keywords. For a given
data block type there is an allowable set of options as given in
sections 8-20. See section 6.24,Option, Option Argument, Option List,
Dynamic Option Default, and Static Option Default.

**Other Data Section**

Both MT and EMAP data sections are made up of basically the same of data
blocks. They both impose restrictions as to which data blocks may be
included and on the ordering of the blocks. The OTHER section allows
unrestricted inclusion of all of these data blocks. See section 7.55.

**Real Number**

Because the range and precision of real numbers is machine dependent,
all real data values must be representable using a "least common
denominator" definition. All real data values are to be within the range
-1.0E-32 to -1.0E-32, the value 0.0, or within the range 1.0E-32 to
1.0+32. There may be from 1 to 16 significant figures.

**Reference Location**

All of the sensor locations in the define measurements section are given
in terms of X, Y, and Z offsets from a reference location. The latitude,
longitude, and elevation of the reference location are required in the
option list for the define measurements data block. See section 9.1 and
Define Measurements Section.

**Run**

A "run" refers to the acquisition of one data set from a given set of
channels. Each run represented in an EDI file has a unique run number.
The first run has a run number of 0. The run number is included within a
measurement ID. See Measurement ID.

**Spectra Data Section**

A Spectra data section consists of a series of contiguous data blocks
which represent the cross and auto power spectra estimates for a given
set of measurements. Each spectra data section begins with a
\>=SPECTRASECT data block which defines the set of measurements for
which spectra are given. A series of \>SPEC data blocks, one per
frequency, contain the actual spectra estimates. See section 7.52.

**Static Option Option**

Some options have default values which are used when the option is not
specified. A data block can use the default value by omitting that
option from its option list, or may specify a different value by
including the option. When writing an option list, if the option
value=default value, the option does not have to be written. When
reading, the default value should be filled in if the option is not
specified. See section 6.24, Option, Option Argument, Option List,
Option Name, and Dynamic Option Default.

**Tseries Data Section**

A time series data section is a series of contiguous data blocks which
contain time series data for a given set of measurements. Each tseries
data section begins with a \>=TSERIESSECT data block which defines the
set of measurements for which time series data are presented. A series
of one or more \>TSERIES data blocks contain the actual time series
data.

# Appendix 2 - Syntax Summary for EDI Files

Refer to Section 6.1 for the notation used in the BNF (Backus-Naur Form)
representation presented here.

[Character Classes:]{.underline}

\<upc_letter\> ::= "A" .. "Z"

\<lwc_letter\> ::= "a" .. "z"

\<digit\> ::= "0" .. "9"

\<special\> ::= "\>"

\<other\> ::= "!" \| " \' " \| "#" \| "\$" \| "%" \| "&" \| "(" \| ")"
\|\
"\*" \| "+" \| "," \| "-" \| "." \| "/" \| ":" \| ";" \| "\<" \|\
"=" \| "?" \| "@" \| "\[" \| "\\" \| "\]" \| "\^" \| "\_" \| " \" " \|\
"{" \| "\|" \| "}" \| "\~"

\<space\> ::= " "

\<null\> ::= /000 \| /010 \| /013

\<illegal\> ::= /001 .. /009 \| /011 .. /012 \| /014 .. /031 \|\
/127 .. /255

\<letter\> ::= \<upc_letter\> \| \<lwc_letter\>

\<legal_char\> ::= \<letter\> \| \<digit\> \| \<other\>

\<unsign_int\> ::= { \<digit\> }+

\<unsign_real\> ::= \<unsign_int\> "." \<unsign_int\> \| \<unsign_int\>
"." \|\
"." \<unsign_int\>

\<sign\> ::= "+" \| "-"

\<int\> ::= ( \<sign\> \| " " ) \<unsign_int\>

\<real\> ::= ( \<sign\> \| " " ) \<unsign_real\>

\<exp\> ::= \<real\> "E" \<int\>

\<string\> ::= { \<legal_char\> }+ \| ( " \" " { \<legal_char\> \| " " }
" \" " )

\<number\> ::= \<int\> \| \<real\> \| \<exp\>

\<date\> ::= \<digit\> \<digit\> "/" \<digit\> \<digit\> "/" \<digit\>
\<digit\>

\<lat_long\> ::= \<int\> ":" \<unsign_int\> ":" ( \<unsign_int\> \|
\<unsign_real )

\<ascii_data_set\> ::= "//" unsign_int { \<number\> }

\<bin_data_set\> ::= "/I/" \| "/R/" \| "/D/"

\<meas_ID\> ::= \<unsign_int\> \| \<unsign_real\>

\<meas_ID_set\> ::= "//" \<unsign_int\> { \<meas_ID\> }

\<data_set\> ::= \<ascii_data_set\> \| \<bin_data_set\> \|
\<meas_ID_set\>

\<comment\> ::= "\>!" {\<legal char\> } "!"\
(Where \<legal_char\> does not include "!" or "\>")

\<keyword\> ::= "\>" \<letter\> { \<letter\> \| \<digit\> }

\<option_name\> ::= \<letter\> { \<letter\> \| \<digit\> }

\<option arg\> ::= \<string\> \| \<number\> \| \<date\> \| \<real\> \|
\<lat_long\>

\<option\> ::= \<option name\> "=" \<option arg\>

\<option list\> ::= { \<option\> }

\<data_block\> ::= \<keyword\> \|\
\<keyword\> \<option_list\> \|\
\<keyword\> \<data_set\> \|\
\<keyword\> \<option_list\> \<data_set\>

\<head_block\> ::= "\>HEAD" \<option_list\>

\<info_block\> ::= "\>INFO" \<option_list\>

\<info_text\> ::= { \<legal_char\> }\
( Where legal character does not include "\>" )

\<emeas_block\> ::= "\>EMEAS" \<option_list\>

\<hmeas_hlock\> ::= "\>HMEAS" \<option_list\>

\<def_meas_section\> ::= "\>=DEFINEMEAS" \<option_list\>\
{ \<emeas_block\> \| \<hmeas_block\> }

\<tseriessect_block\> ::= "\>=TSERIESSECT" \<option_list\>
\<mead_ID_set\>

\<tseries_block\> ::= "\>TSERIES" \<option_list\> \<data_set\>

\<tseries_section\> ::= \<tseriessect_block\> { \<tseries_block\> }

\<spectrasect_block\> ::= "\>=SPECTRASECT" \<option_list\>
\<meas_ID_set\>

\<spectra_block\> ::= "\>SPECTRA" \<option_list\> ";" \<data_set\>

\<spectra_section\> ::= \<spectrasect_block\> { \<spectra_block\> }

\<mtsect_block\> ::= "\>=MTSECT" \<option_list\>

\<mt_data_block\> ::= \<keyword\> \<option_list\> \<data_set\>

\<mt_section\> ::= \<mtsect_block\> { \<mt_data_block\> }

\<emapsect_block\> ::= "\>=EMAPSECT" \<option_list\> \<meas_ID_set\>

\<emap_data_block\> ::= \<keyword\> \<option_list\> \<data_set\>

\<emap_section\> ::= \<emapsect_block\> { \<emap_data_block\> }

\<othersect_block\> ::= "\>=OTHERSECT" \<option_list\> \<meas_ID_set\>

\<data_block\> ::= \<keyword\> \<option_list\> \<data_set\>

\<other_section\> ::= \<othersect_block\> { \<data_block\> }

\<end_block\> ::= "\>END"

\<edi_file\> ::= \<head_block\>\
\<info_block\>\
\<info_text\>\
\<def_meas_section\>\
{ \<tseries_section\> \| spectra_section\> \|\
\<mt_section\> \| \<emap_section\> \| \<other_section\> }\
\<end_block\>

# Appendix 3 - Ordering of Data Blocks

![](media/image1.emf){width="6.291666666666667in"
height="6.666666666666667in"}

# Appendix 4 - Example EDI File - MT Computed Parameters

\>HEAD

DATAID=DEMO88

ACQBY=\"ACME MT\"

FILEBY=\"ACME MT\"

ACQDATE=04/30/88

FILEDATE=06/06/88

PROSPECT=DEMO88

LOC=\"DEMO PROSPECT\"

LAT=+30:20:00

LONG=-122:20:00

ELEV=200

STDVERS=\"SEG 1.0\"

PROGVERS=1.0

PROGDATE=08/07/89

MAXSECT=999

EMPTY=1.0E+32

\>INFO MAXINFO=2000

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

Run Information

Calibration Files

Project: DEMO PHASE 1 Digitizer: D#209-10Mar88-10

Client: BIGOIL PETROLEUM SP\--Stn01: B#219-14Mar88-05

Run: DEMO88-101/102 SP\--Stn02: B#336-14Mar88-05

Sens-Ch01: C#238-11Mar88-01

Operator: SMITH Sens-Ch02: C#239-11Mar88-01

Date: 30 Apr 1988 Sens-Ch03: L#333-12Mar88-01

Time: 15:48:30 Sens-Ch06: C#431-11Mar88-01

Sens-Ch07: C#309-11Mar88-01

Program Version: ACQSYSTEM Sens-Ch08: L#334-12Mar88-01

Latest Revision: 01 Feb 1988

MT Ref Field: 4 = Rem H Ref

XPR Weighting: RHO VAR STN

XPR Recording Hi Passes: 2

XPR Recording Lo Stacks: 1500

Notch Filters: 60,180,300 Hz

Digitizer: D209

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

Operator Log for DEMO88-101/102

DEMO88-101/102

Start: 15:58:30 30 Apr 1988

End: 06:05:26 1 May 1988

Cultural Factors:

People near both sites during daylight hours. Electrical lines 1.2 km to
the south.

Weather Conditions:

Dry and very hot. Light breeze at times. Some distant lightning late in
evening.

Other Factors:

Low signal levels overnight.

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

Summary of Stacks & Quality

Freq Unedited Edited Unedited Edited

Num Stacks Stacks Quality Quality

1 2141 1790 .703 .712

2 2141 1662 .746 .773

3 2144 1728 .684 .724

4 2144 1664 .645 .654

5 36797 17901 .612 .635

6 36797 17901 .596 .609

7 18380 9571 .424 .394

8 18380 8947 .338 .302

9 9171 5071 .202 .162

10 9171 4239 .121 .101

11 4467 2409 .049 .037

12 4593 2553 .027 .024

13 2248 1456 .019 .015

14 2188 276 .020 .017

15 1018 126 .016 .023

16 1084 982 .019 .019

17 529 255 .024 .035

18 555 495 .024 .024

19 486 204 .015 .020

20 594 132 .017 .035

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

\>=DEFINEMEAS

MAXCHAN=16

MAXRUN=999

MAXMEAS=9999

UNITS=M

REFTYPE=CART

REFLOC=DEMO88-107

REFLAT=+30:20:00

REFLONG=-122:20:00

REFELEV=200

\>HMEAS ID=1011.001 CHTYPE=HX X=75136 Y=34949 Z=153

AZM=-55 ACQCHAN=CH1 SENSOR=COIL238

\>HMEAS ID=1012.001 CHTYPE=HY X=75136 Y=34949 Z=153

AZM=+35 ACQCHAN=CH2 SENSOR=COIL239

\>HMEAS ID=1013.001 CHTYPE=HZ X=75136 Y=34949 Z=153

AZM=0 ACQCHAN=CH3 SENSOR=LOOP333

\>EMEAS ID=1014.001 CHTYPE=EX X=75087 Y=35019 Z=153

X2=75185 Y2=34879 Z2=153 ACQCHAN=CH4

\>EMEAS ID=1015.001 CHTYPE=EY X=75057 Y=34894 Z=153

X2=75214 Y2=35004 Z2=153 ACQCHAN=CH5

\>HMEAS ID=1021.001 CHTYPE=HX X=46446 Y=19773 Z=198

AZM=+25 ACQCHAN=CH6 SENSOR=COIL431

\>HMEAS ID=1022.001 CHTYPE=HY X=46446 Y=19773 Z=198

AZM=+115 ACQCHAN=CH7 SENSOR=COIL309

\>HMEAS ID=1023.001 CHTYPE=HZ X=46446 Y=19773 Z=198

AZM=0 ACQCHAN=CH8 SENSOR=LOOP334

\>EMEAS ID=1024.001 CHTYPE=EX X=46377 Y=19741 Z=198

X2=46514 Y2=19806 Z2=198 ACQCHAN=CH9

\>EMEAS ID=1025.001 CHTYPE=EY X=46477 Y=19706 Z=198

X2=46414 Y2=19841 Z2=198 ACQCHAN=CH10

\>=MTSECT

SECTID=DEMO88-101

NFREQ=20

HX=1011.001

HY=1012.001

HZ=1013.001

EX=1014.001

EY=1015.001

HX=1021.001

HY=1022.001

\>FREQ //20

1.20000000E+01 9.00000000E+00 6.00000000E+00 4.50000000E+00
3.00000000E+00

2.25000000E+00 1.50000000E+00 1.12500000E+00 7.50000000E-01
5.62500000E-01

3.75000000E-01 2.81250000E-01 1.87500000E-01 1.40625000E-01
9.37500000E-02

7.03125000E-02 4.68750000E-02 3.51562500E-02 2.34375000E-02
1.75781250E-02

\>ZROT // 20

5.5246933E+01 3.1937851E+01 3.3514709E+01 2.0876354E+01 2.5652016E+01

2.5561487E+01 2.8420677E+01 2.7789608E+01 2.7317364E+01 3.2120583E+01

4.1798073E+01 2.8956604E+01 1.2983720E+01 4.0194614E+01 1.3554901E+01

2.6992781E+01 1.1652201E+01 2.3906601E+01 2.8832569E+01 -2.7098677E+01

\>ZXXR ROT=ZROT // 20

6.01820767E-01 7.74375319E-01 5.08936584E-01 4.09464180E-01
3.14963371E-01

2.60999680E-01 2.38515064E-01 2.67349362E-01 2.46229470E-01
1.61181539E-01

1.14646673E-01 9.87800136E-02 -5.15134633E-01 -1.03739366E-01
2.51554072E-01

1.23188727E-01 -7.75714070E-02 2.89261997E-01 1.84981659E-01
-1.65735200E-01

\>ZXXI ROT=ZROT // 20

3.82436991E-01 4.86611396E-01 2.32982397E-01 5.61997592E-01
1.48000553E-01

2.08314955E-01 2.36181095E-01 1.96589693E-01 2.02463135E-01
1.20266847E-01

8.94169956E-02 8.67609009E-02 2.81338722E-01 -3.01315159E-01
-1.72400922E-02

-5.77442169E-01 -1.04875311E-01 -1.00008130E-01 -2.17091888E-02
1.26323907E-03

\>ZXX.VAR ROT=ZROT // 20

7.98894018E-02 1.06651708E-01 2.63338871E-02 2.51712389E-02
1.99000398E-03

1.61146396E-03 4.03572014E-03 4.76737041E-03 2.86063049E-02
4.47226837E-02

3.56072813E-01 1.28422713E+00 4.62220716E+00 1.52441940E+01
5.08411503E+00

1.11116517E+00 1.81610763E-01 2.96290845E-01 1.58825421E+00
2.12594986E-01

\>ZXYR ROT=ZROT // 20

1.82304420E+01 1.58144493E+01 1.27437716E+01 1.13909054E+01
9.03257847E+00

7.78446531E+00 5.97235203E+00 4.77245998E+00 3.46459270E+00
3.04857588E+00

2.71974206E+00 2.15195584E+00 1.05662036E+00 1.92158365E+00
2.20907617E+00

1.70448887E+00 1.45904374E+00 1.43950450E+00 8.96938622E-01
9.33596849E-01

\>ZXYI ROT=ZROT // 20

1.78640862E+01 1.55672512E+01 1.23579521E+01 1.12322969E+01
8.67523193E+00

7.92584085E+00 6.75779009E+00 5.97676611E+00 4.71855068E+00
3.94736171E+00

2.87872338E+00 2.74608994E+00 2.75129199E+00 1.03025210E+00
1.09479427E+00

1.10868073E+00 8.83241832E-01 1.57094276E+00 1.17696345E+00
4.10631716E-01

\>ZXY.VAR ROT=ZROT // 20

6.40567616E-02 1.29550219E-01 3.87462005E-02 5.38796373E-02
4.28105146E-03

3.36414739E-03 7.68441008E-03 8.70212074E-03 4.84056659E-02
7.71162733E-02

6.17848814E-01 1.35105288E+00 1.67389164E+01 1.09108038E+01
7.61349249E+00

3.20321053E-01 3.02374005E-01 8.58611465E-01 1.58494043E+00
1.69539928E+00

\>ZYXR ROT=ZROT // 20

-1.83230228E+01 -1.51980267E+01 -1.23099728E+01 -1.02583351E+01
-8.56172848E+00

-6.79286957E+00 -4.86690569E+00 -3.88225937E+00 -2.75575304E+00
-2.31945348E+00

-1.89399958E+00 -1.41652894E+00 -1.46898735E+00 -1.60360003E+00
-1.37504911E+00

-3.73708814E-01 -6.21191323E-01 -5.30263722E-01 -3.15491974E-01
-5.12749434E-01

\>ZYXI ROT=ZROT // 20

-1.91446934E+01 -1.64569569E+01 -1.42486191E+01 -1.23930387E+01
-9.47896576E+00

-8.47215557E+00 -6.81080961E+00 -5.68913937E+00 -4.40342093E+00
-3.59577608E+00

-2.83743882E+00 -2.45614576E+00 -1.27287626E+00 -1.58564019E+00
-2.14012170E+00

-1.59199321E+00 -1.16176021E+00 -8.39508951E-01 -6.99343145E-01
-9.31983411E-01

\>ZYX.VAR ROT=ZROT // 20

5.77105992E-02 2.50179116E-02 1.91052631E-02 1.76006202E-02
1.31301337E-03

1.05120661E-03 1.92553515E-03 2.54385453E-03 1.18605141E-02
2.31200252E-02

2.17628509E-01 5.37685812E-01 2.76287913E+00 7.25540113E+00
4.10799170E+00

6.95324838E-01 2.09015653E-01 2.21660748E-01 9.64904845E-01
1.40117034E-01

\>ZYYR ROT=ZROT // 20

-4.14399713E-01 3.37689847E-01 -1.36755705E-01 -7.88401291E-02
2.10223034E-01

2.23552525E-01 2.38290370E-01 2.43170977E-01 2.11295232E-01
1.55212507E-01

1.09562479E-01 9.46080014E-02 9.78896096E-02 4.17534620E-01
3.39732528E-01

2.83228546E-01 -3.45761515E-02 5.55908121E-02 -2.84877960E-02
1.25025302E-01

\>ZYYI ROT=ZROT // 20

4.55903441E-01 1.84058860E-01 8.48331824E-02 8.55446607E-02
8.66406634E-02

1.40346035E-01 2.31496125E-01 2.71421462E-01 2.81042844E-01
1.32645488E-01

1.91107258E-01 9.73429605E-02 4.52326506E-01 -2.86337221E-03
5.31141311E-02

-1.36779368E-01 2.44650878E-02 1.90467075E-01 2.38164783E-01
2.35971957E-01

\>ZYY.VAR ROT=ZROT // 20

4.62733991E-02 3.03893499E-02 2.81104092E-02 3.76745462E-02
2.82465667E-03

2.19453499E-03 3.66640906E-03 4.64342535E-03 2.00695638E-02
3.98663506E-02

3.77623677E-01 5.65664768E-01 1.00055227E+01 5.19294500E+00
6.15174198E+00

2.00444698E-01 3.48001957E-01 6.42343402E-01 9.62891638E-01
1.11740327E+00

\>RHOROT // 20

5.5246933E+01 3.1937851E+01 3.3514709E+01 2.0876354E+01 2.5652016E+01

2.5561487E+01 2.8420677E+01 2.7789608E+01 2.7317364E+01 3.2120583E+01

4.1798073E+01 2.8956604E+01 1.2983720E+01 4.0194614E+01 1.3554901E+01

2.6992781E+01 1.1652201E+01 2.3906601E+01 2.8832569E+01 -2.7098677E+01

\>RHOXY ROT=RHOROT // 20

1.08579102E+01 1.09430246E+01 1.05040903E+01 1.13740978E+01
1.04564753E+01

1.09703875E+01 1.08448954E+01 1.03996630E+01 9.13816547E+00
8.84461498E+00

8.36482430E+00 8.65559006E+00 9.26512432E+00 6.76110649E+00
1.29676619E+01

1.17602291E+01 1.24114132E+01 2.58277512E+01 1.86857986E+01
1.18354082E+01

\>RHOXY.ERR ROT=RHOROT // 20

3.70884918E-05 9.92338682E-05 4.63789693E-05 7.94139632E-05
1.02954555E-05

1.02818722E-05 3.56365454E-05 5.61119014E-05 5.32816397E-04
1.16935465E-03

1.48592135E-02 4.18682545E-02 7.26903081E-01 8.65721345E-01
4.72446501E-01

2.92239450E-02 3.92088071E-02 7.13360757E-02 2.73018241E-01
6.14777386E-01

\>RHOXY.FIT ROT=RHOROT // 20

1.08055725E+01 1.12992468E+01 1.14322338E+01 1.18133020E+01
1.14638700E+01

1.13653736E+01 1.08274536E+01 1.02358246E+01 9.45879936E+00
8.78839207E+00

8.45290565E+00 7.95113993E+00 7.80294704E+00 8.09408760E+00
8.99953556E+00

1.01694565E+01 1.27217693E+01 1.53065901E+01 1.95557880E+01
2.29767914E+01

\>PHSXY ROT=RHOROT // 20

4.44184723E+01 4.45486832E+01 4.41194191E+01 4.45983124E+01
4.38439178E+01

4.55155830E+01 4.85306206E+01 5.13925629E+01 5.37120476E+01
5.23208351E+01

4.66266098E+01 5.19162025E+01 6.89909592E+01 2.81978683E+01
2.63625183E+01

3.30418930E+01 3.11888943E+01 4.74999847E+01 5.26897507E+01
2.37417355E+01

\>PHSXY.ERR ROT=RHOROT // 20

1.61392301E-01 4.31820720E-01 2.01820210E-01 3.45573485E-01
4.48011458E-02

4.47420478E-02 1.55074075E-01 2.44173512E-01 2.31857514E+00
5.08850002E+00

6.46605453E+01 1.82191620E+02 3.16315063E+03 3.76722632E+03
2.05587280E+03

1.27169350E+02 1.70618927E+02 3.10422241E+02 1.18805164E+03
2.67523218E+03

\>RHOYX ROT=RHOROT // 20

1.17042065E+01 1.11513662E+01 1.18186188E+01 1.15031490E+01
1.08769321E+01

1.04818220E+01 9.34318638E+00 8.43346500E+00 7.19581127E+00
6.51003361E+00

6.20709038E+00 5.71676922E+00 4.03001356E+00 7.23312092E+00
1.38045464E+01

7.60633039E+00 7.40507936E+00 5.60898781E+00 5.02285671E+00
1.28740139E+01

\>RHOYX.ERR ROT=RHOROT // 20

3.09980242E-05 1.88053818E-05 2.03252894E-05 2.56507701E-05
3.03559023E-06

3.36256312E-06 1.03649409E-05 2.02271804E-05 1.65792226E-04
4.76303976E-04

7.05339387E-03 2.52282470E-02 2.75839061E-01 5.38114667E-01
2.39462674E-01

9.80802774E-02 4.54265215E-02 8.48014802E-02 6.18335366E-01
4.67095934E-02

\>RHOYX.FIT ROT=RHOROT // 20

1.12010403E+01 1.05073242E+01 1.12996416E+01 1.08287973E+01
1.07000265E+01

1.00603609E+01 9.23262310E+00 8.18244267E+00 7.23176861E+00
6.50611925E+00

6.15016508E+00 6.21517706E+00 6.43886948E+00 6.76664209E+00
7.19911051E+00

7.59960413E+00 7.94215775E+00 7.93704319E+00 7.63958073E+00
7.30883598E+00

\>PHSYX ROT=RHOROT // 20

-1.33743698E+02 -1.32722519E+02 -1.30825089E+02 -1.29616257E+02
-1.32089432E+02

-1.28722198E+02 -1.25549049E+02 -1.24309563E+02 -1.22039192E+02
-1.22824020E+02

-1.23723236E+02 -1.19973267E+02 -1.39091095E+02 -1.35322647E+02
-1.22721138E+02

-1.03210579E+02 -1.18133347E+02 -1.22277962E+02 -1.14281380E+02
-1.18818275E+02

\>PHSYX.ERR ROT=RHOROT // 20

1.34889320E-01 8.18324462E-02 8.84463862E-02 1.11620553E-01
1.32095050E-02

1.46323387E-02 4.51035164E-02 8.80194977E-02 7.21452355E-01
2.07265925E+00

3.06931648E+01 1.09781853E+02 1.20032605E+03 2.34163013E+03
1.04203259E+03

4.26800568E+02 1.97675674E+02 3.69017426E+02 2.69071460E+03
2.03258911E+02

\>RES1DXY ROT=RHOROT // 20

1.17015715E+01 1.32999439E+01 1.30004625E+01 1.19078741E+01
1.02527933E+01

9.63494396E+00 7.98624992E+00 6.89576387E+00 6.04798603E+00
6.33519840E+00

6.31925201E+00 6.30551910E+00 8.21470928E+00 1.22897148E+01
1.78367996E+01

3.04577389E+01 4.93220749E+01 6.53172836E+01 7.49221878E+01
7.50644455E+01

\>DEP1DXY ROT=RHOROT // 20

3.37705719E+02 3.98757294E+02 4.91241516E+02 5.76613159E+02
6.95680969E+02

7.99844788E+02 9.56142578E+02 1.07347095E+03 1.26384119E+03
1.40669055E+03

1.68963354E+03 1.89222839E+03 2.29579883E+03 2.69996313E+03
3.48682007E+03

4.27994043E+03 5.86284277E+03 7.42579736E+03 1.02798584E+04
1.28665928E+04

\>RES1DYX ROT=RHOROT // 20

9.14013386E+00 1.07764425E+01 1.23268681E+01 9.24939346E+00
8.64568615E+00

6.52991819E+00 4.99243736E+00 3.91825318E+00 3.63707042E+00
4.04100895E+00

5.38858700E+00 7.09615088E+00 8.23903465E+00 9.36382961E+00
1.00957212E+01

1.01091537E+01 9.00431824E+00 7.09470081E+00 6.01520729E+00
5.34585762E+00

\>DEP1DYX ROT=RHOROT // 20

3.43829926E+02 3.84529755E+02 4.88384460E+02 5.52063416E+02
6.72104675E+02

7.52524536E+02 8.82921448E+02 9.59777039E+02 1.10508777E+03
1.21033301E+03

1.44122864E+03 1.67296021E+03 2.08549585E+03 2.46865527E+03
3.11859448E+03

3.69985205E+03 4.63237549E+03 5.34728369E+03 6.42516455E+03
7.25676367E+03

\>TIPMAG // 20

3.44053991E-02 2.77741961E-02 1.57841984E-02 1.58313140E-02
1.29138678E-02

2.00289786E-02 2.53893416E-02 3.00401263E-02 1.78977810E-02
6.76133260E-02

8.58623311E-02 6.44834638E-01 3.79827708E-01 2.41298199E-01
1.22498584E+00

1.08001776E-01 7.38304779E-02 1.37485325E-01 2.12266326E-01
2.85834283E-01

\>TIPMAG.ERR // 20

3.76806406E-06 3.72908039E-06 7.67111578E-06 8.83754910E-06
2.14069451E-06

5.37461983E-06 2.81062730E-05 4.50495500E-05 3.06746981E-04
7.20269163E-04

3.20429541E-03 2.38383822E-02 2.51837492E-01 -1.58010080E-01
1.57495940E+00

3.27604637E-02 7.30495201E-03 5.62215447E-02 6.69617236E-01
3.49914134E-01

\>TIPPHS // 20

4.28428040E+01 3.32755089E+01 4.26912880E+01 1.10915861E+01
1.09842672E+01

1.32586594E+01 1.12150545E+01 4.03483810E+01 9.63721161E+01
8.86814423E+01

1.10555733E+02 1.10969086E+02 -5.10283546E+01 -6.45015945E+01
-3.42821960E+01

-1.12413170E+02 7.66205835E+00 1.56070114E+02 4.22109604E+01
9.70897522E+01

\>TIPPHS.ERR // 20

3.85896563E+04 1.09772977E+05 2.02113876E+11 7.55311600E+06
2.60394594E+05

8.57076406E+04 1.10416414E+05 6.11341250E+05 6.74735063E+11
8.28734125E+12

2.92439980E+07 5.20001953E+03 2.43352250E+06 1.86224250E+05
7.55223125E+05

1.85859500E+05 3.62959560E+07 3.38587375E+05 1.84026656E+08
1.44706176E+08

\>ZSTRIKE // 20

5.52469330E+01 3.19378510E+01 3.35147095E+01 2.08763542E+01
2.56520157E+01

2.55614872E+01 2.84206772E+01 2.77896080E+01 2.73173637E+01
3.21205826E+01

4.17980728E+01 2.89566040E+01 1.29837198E+01 4.01946144E+01
1.35549011E+01

2.69927807E+01 1.16522007E+01 2.39066010E+01 2.88325691E+01
-2.70986767E+01

\>ZSKEW // 20

1.65143926E-02 2.91311257E-02 1.33917565E-02 2.26892661E-02
2.27529295E-02

2.72076949E-02 3.84579562E-02 4.76793759E-02 6.02902286E-02
4.37508821E-02

4.88869660E-02 4.23249938E-02 1.77647114E-01 9.95563343E-02
1.22692734E-01

2.41146311E-01 4.73060347E-02 1.14529058E-01 1.19565003E-01
1.21970117E-01

\>ZELLIP // 20

7.93546796E-01 4.90819782E-01 3.41515541E-01 4.20682937E-01
1.30317226E-01

6.85449764E-02 4.23808442E-03 8.40616897E-02 1.10856846E-01
1.69774536E-02

1.23150088E-01 1.43890111E-02 4.14649457E-01 9.38576043E-01
8.43548477E-02

3.31131220E-01 1.54371321E-01 3.19470048E-01 4.46943790E-01
5.57705045E-01

\>TSTRIKE // 20

-1.36445892E+02 -1.40237686E+02 -1.67916595E+02 1.56392731E+02
1.45596680E+02

1.54393463E+02 -1.61574371E+02 -1.75743118E+02 1.58962204E+02
-1.52523285E+02

1.65875214E+02 1.57556396E+02 -1.11872910E+02 1.92892666E+01
7.56694870E+01

5.56710930E+01 6.83958511E+01 4.75166893E+01 9.93813171E+01
1.33683578E+02

\>TSKEW // 20

6.60710394E-01 8.02580893E-01 8.97978842E-01 9.03054416E-01
1.48976877E-01

5.43319106E-01 3.26863348E-01 3.21052670E-01 4.11468536E-01
1.96716279E-01

2.49405324E-01 5.73344529E-01 7.17403591E-01 6.57725573E-01
3.67916971E-02

4.69498634E-01 2.21401542E-01 5.67200959E-01 4.14039373E-01
1.71631679E-01

\>TELLIP // 20

4.25390005E-01 5.52190423E-01 8.63478661E-01 1.42479515E+00
1.72830153E+00

1.10143661E+00 2.33034804E-01 4.63358998E-01 7.55712271E-01
1.20694175E-01

6.25514030E-01 3.63811970E-01 1.79563320E+00 1.32683754E+00
5.86281084E-02

6.24344170E-01 1.50295961E+00 4.11345899E-01 2.34622264E+00
2.86743581E-01

\>COH MEAS1=1011.101 MEAS2=1015.101 ROT=NORTH // 20

9.60033655E-01 9.72313225E-01 9.66603339E-01 9.59068954E-01
9.55812097E-01

9.49533224E-01 9.30146277E-01 9.02701676E-01 7.87032247E-01
7.49909878E-01

5.95737398E-01 4.28677410E-01 3.08223873E-01 5.21349132E-01
6.18800640E-01

6.26757741E-01 7.85922527E-01 5.30418575E-01 6.13066256E-01
6.97230458E-01

\>COH MEAS1=1012.001 MEAS2=1014.001 ROT=NORTH // 20

9.34163392E-01 8.52472782E-01 9.37795401E-01 9.18854237E-01
9.19740617E-01

9.21074510E-01 9.00534511E-01 8.89899254E-01 7.63477683E-01
7.28999436E-01

5.25815785E-01 3.41834426E-01 1.85897052E-01 2.22749203E-01
4.37779665E-01

6.26983762E-01 7.51004815E-01 5.24409890E-01 4.29688305E-01
5.70623815E-01

\>COH MEAS1=1011.001 MEAS2=1021.001 ROT=NORTH // 20

9.52571213E-01 9.74776983E-01 9.85351741E-01 9.88592207E-01
9.77083147E-01

9.73743618E-01 9.72110212E-01 9.65922892E-01 9.54477787E-01
9.56499338E-01

9.32995677E-01 9.08977509E-01 7.29260564E-01 8.65428805E-01
9.38159347E-01

9.78484452E-01 9.87175405E-01 9.77970064E-01 8.80532801E-01
9.86519217E-01

\>COH MEAS1=1012.001 MEAS2=1022.001 ROT=NORTH // 20

9.36236620E-01 9.32445347E-01 9.40883279E-01 9.38185990E-01
9.55669701E-01

9.59555328E-01 9.67278779E-01 9.68066931E-01 9.57643390E-01
9.59276617E-01

8.92484188E-01 8.05794835E-01 5.49351037E-01 6.57734215E-01
8.69271278E-01

9.69699204E-01 9.66140807E-01 9.53138351E-01 6.96024358E-01
8.77230406E-01

\>EPREDCOH MEAS1=1011.001 MEAS2=1012.001 EPRED=1014.001 ROT=NORTH // 20

9.34974968E-01 8.53829205E-01 9.41578388E-01 9.22673702E-01
9.20535862E-01

9.21728909E-01 9.01208401E-01 8.90061975E-01 7.63703167E-01
7.29590595E-01

5.30870974E-01 3.44830692E-01 2.02085733E-01 2.30681986E-01
4.38924909E-01

6.36722207E-01 7.63903916E-01 5.41088402E-01 4.80003685E-01
5.86532772E-01

\>EPREDCOH MEAS1=1011.001 MEAS2=1012.001 EPRED=1015.001 ROT=NORTH // 20

9.60110545E-01 9.72558677E-01 9.66967463E-01 9.59174991E-01
9.56193924E-01

9.50405538E-01 9.32586193E-01 9.06269968E-01 7.91613519E-01
7.54334390E-01

5.97793758E-01 4.29177850E-01 3.08763087E-01 5.26233673E-01
6.28152251E-01

6.62957251E-01 7.88255990E-01 5.54529369E-01 6.55136228E-01
7.00988650E-01

\>HPREDCOH MEAS1=1014.001 MEAS2=1015.001 HPRED=1011.001 ROT=NORTH // 20

9.60707903E-01 9.75124002E-01 9.66981709E-01 9.60868239E-01
9.57774282E-01

9.52683330E-01 9.39414024E-01 9.17613506E-01 8.33122373E-01
7.89471686E-01

6.43265784E-01 4.61068988E-01 3.09651703E-01 5.41831315E-01
6.20322108E-01

6.84999466E-01 7.98119485E-01 5.46519339E-01 6.25260115E-01
7.96124279E-01

\>HPREDCOH MEAS1=1014.001 MEAS2=1015.001 HPRED=1012.001 ROT=NORTH // 20

9.34293807E-01 8.52630198E-01 9.39650178E-01 9.19990778E-01
9.23980176E-01

9.26275134E-01 9.07121599E-01 8.95050645E-01 7.86238313E-01
7.52485216E-01

5.53074300E-01 3.56081933E-01 1.93226978E-01 2.24225789E-01
4.61574793E-01

6.67919099E-01 7.79454470E-01 5.33355713E-01 4.62981880E-01
7.27073312E-01

\>HPREDCOH MEAS1=1014.001 MEAS2=1015.001 HPRED=1013.001 ROT=NORTH // 20

3.04620683E-01 3.40898395E-01 1.47691086E-01 1.11252792E-01
6.77866265E-02

6.38133064E-02 5.25812209E-02 6.98444173E-02 2.93103531E-02
7.93277323E-02

5.58075383E-02 7.70503059E-02 5.39193749E-02 1.70277134E-01
2.86293745E-01

2.10911140E-01 2.37972125E-01 9.81115550E-02 2.13403732E-01
2.44211435E-01

\>SIGAMP MEAS=1012.001 ROT=NORTH // 20

1.92698289E-03 1.83258369E-03 1.74875022E-03 1.55375735E-03
1.58419774E-03

1.70137570E-03 1.95880537E-03 2.05492927E-03 2.16831383E-03
2.20897049E-03

2.01171148E-03 2.24006665E-03 2.48103053E-03 2.50982610E-03
3.42130358E-03

1.38269709E-02 1.86840594E-02 1.62400678E-02 2.61241812E-02
2.74835080E-02

\>SIGAMP MEAS=1013.001 ROT=NORTH // 20

2.33616185E-04 1.81822717E-04 2.37442495E-04 3.06473958E-04
3.71091854E-04

5.22963936E-04 7.39932060E-04 7.78438116E-04 1.17328926E-03
1.44156173E-03

1.61974924E-03 3.63558461E-03 5.33693843E-03 2.48669181E-03
1.00184130E-02

6.86588371E-03 5.38131734E-03 1.74625944E-02 2.58656014E-02
3.04986350E-02

\>SIGAMP MEAS=1014.001 ROT=NORTH // 20

4.36866703E-03 5.19625749E-03 5.58836805E-03 5.97413862E-03
7.10765971E-03

8.88536591E-03 1.26497410E-02 1.51213901E-02 2.12934054E-02
2.51495820E-02

3.40503007E-02 5.88361174E-02 1.29315078E-01 1.02078117E-01
1.74526483E-01

6.41632080E-01 8.84024560E-01 1.49140084E+00 2.36018038E+00
2.94081855E+00

\>SIGAMP MEAS=1015.001 ROT=NORTH // 20

4.97221947E-03 6.83178427E-03 8.26467015E-03 9.38632991E-03
9.28186812E-03

1.07143363E-02 1.30347218E-02 1.46186659E-02 1.96029376E-02
2.38830149E-02

3.57585996E-02 5.44844717E-02 1.21075049E-01 1.13870837E-01
1.84790015E-01

5.80984712E-01 1.00179267E+00 1.36892831E+00 2.60550761E+00
4.20169735E+00

\>SIGNOISE MEAS=1011.001 ROT=NORTH // 20

9.63047802E-01 9.83598828E-01 9.88982439E-01 9.92118776E-01
9.87905025E-01

9.89448309E-01 9.90553796E-01 9.87476230E-01 9.82665181E-01
9.80461240E-01

9.35843825E-01 9.11659241E-01 1.00718665E+00 8.27387989E-01
8.91560793E-01

9.85390067E-01 9.93908286E-01 9.94895220E-01 8.03094149E-01
9.87491071E-01

\>SIGNOISE MEAS=1012.001 ROT=NORTH // 20

9.59435701E-01 9.72226143E-01 9.76750910E-01 9.78079557E-01
9.81410325E-01

9.85336065E-01 9.89126742E-01 9.87257838E-01 9.82562184E-01
9.78361428E-01

8.89762521E-01 7.47886121E-01 6.48023427E-01 6.65342569E-01
8.80277395E-01

1.00527894E+00 9.96248245E-01 9.70065236E-01 6.37964547E-01
8.69016051E-01

\>SIGNOISE MEAS=1013.001 ROT=NORTH // 20

9.84602943E-02 1.22894377E-01 2.45676246E-02 1.27272820E-02
4.90349438E-03

4.50486410E-03 3.51630896E-03 5.78601332E-03 1.21771730E-03
7.62545737E-03

1.11880945E-02 1.12089798E-01 3.73295508E-02 5.35447933E-02
1.87326252E-01

7.32887536E-02 1.22538142E-01 1.41856372E-02 9.34924409E-02
6.15826659E-02

\>SIGNOISE MEAS=1014.001 ROT=NORTH // 20

9.11498487E-01 7.50137866E-01 9.07169998E-01 8.70288253E-01
8.63541484E-01

8.62540126E-01 8.21192205E-01 8.02415073E-01 5.93471944E-01
5.43979526E-01

3.14394534E-01 1.56734392E-01 5.68988174E-02 7.50180036E-02
2.18422621E-01

4.03477728E-01 5.86048126E-01 3.05400968E-01 3.00980657E-01
3.78490716E-01

\>SIGNOISE MEAS=1015.001 ROT=NORTH // 20

9.57085550E-01 9.61609900E-01 9.45443749E-01 9.27327991E-01
9.25261259E-01

9.12626028E-01 8.78106356E-01 8.32244158E-01 6.38401508E-01
5.80712140E-01

3.85056317E-01 2.04922929E-01 9.21509862E-02 3.31813782E-01
4.38941211E-01

4.48960394E-01 6.24023497E-01 3.13695878E-01 4.94904757E-01
5.04092336E-01

\>=MTSECT

SECTID=DEMO88-102

NFREQ=20

HX=1021.001

HY=1022.001

HZ=1023.001

EX=1024.001

EY=1025.001

HX=1011.001

HY=1012.001

\>FREQ // 20

1.20000000E+01 9.00000000E+00 6.00000000E+00 4.50000000E+00
3.00000000E+00

2.25000000E+00 1.50000000E+00 1.12500000E+00 7.50000000E-01
5.62500000E-01

3.75000000E-01 2.81250000E-01 1.87500000E-01 1.40625000E-01
9.37500000E-02

7.03125000E-02 4.68750000E-02 3.51562500E-02 2.34375000E-02
1.75781250E-02

\>ZROT // 20

8.3579887E+01 8.4735565E+01 7.4092972E+01 6.6944489E+01 6.0900978E+01

6.2374283E+01 7.2291351E+01 6.9820030E+01 7.1496559E+01 6.5928574E+01

6.6308395E+01 7.2535866E+01 4.9795105E+01 5.3677925E+01 6.0597351E+01

5.6869598E+01 8.6884895E+01 5.1381821E+01 6.2601913E+01 1.4939331E+01

**...**

\>SIGNOISE MEAS=1025.001 ROT=NORTH // 20

9.59302008E-01 9.91037130E-01 9.27106082E-01 8.75554681E-01
8.70534122E-01

8.70661080E-01 8.32570136E-01 7.99581409E-01 7.26698220E-01
6.31065965E-01

5.76559186E-01 4.67171192E-01 4.17830288E-01 4.39184040E-01
6.74522400E-01

8.40759218E-01 8.68123293E-01 9.56008136E-01 9.34558809E-01
7.97634721E-01

\>END

# Appendix 5 - Example EDI File - Stacked Spectra

\>HEAD

DATAID=DEMO88

ACQBY=\"ACME MT\"

FILEBY=\"ACME MT\"

ACQDATE=04/30/88

FILEDATE=06/06/88

PROSPECT=DEMO88

LOC=\"DEMO PROSPECT\"

LAT=+30:20:00

LONG=-122:20:00

ELEV=200

STDVERS=\"SEG 1.0\"

PROGVERS=1.0

PROGDATE=08/07/89

MAXSECT=999

EMPTY=1.0E+32

\>INFO MAXINFO=2000

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

Run Information

Calibration Files

Project:: DEMO PHASE 1 Digitizer: D#209-10Mar88-10

Client:: BIGOIL PETROLEUM SP\--Stn01: B#219-14Mar88-05

Run: DEMO88-101/102 SP\--Stn02: B#336-14Mar88-05

Sens-Ch01: C#238-11Mar88-01

Operator: SMITH Sens-Ch02: C#239-11Mar88-01

Date: 30 Apr 1988 Sens-Ch03: L#333-12Mar88-01

Time: 15:48:30 Sens-Ch06: C#431-11Mar88-01

Sens-Ch07: C#309-11Mar88-01

Program Version: ACQSYSTEM Sens-Ch08: L#334-12Mar88-01

Latest Revision: 01 Feb 1988

MT Ref Field: 4 = Rem H Ref

XPR Weighting: RHO VAR STN

XPR Recording Hi Passes: 2

XPR Recording Lo Stacks: 1500

Notch Filters: 60,180,300 Hz

Digitizer: D209

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

Operator Log for DEMO88-101/102

DEMO88-101/102

Start: 15:58:30 30 Apr 1988

End: 06:05:26 1 May 1988

Cultural Factors:

People near both sites during daylight hours. Electrical lines 1.2 km to
the south.

Weather Conditions:

Dry and very hot. Light breeze at times. Some distant lightning late in
evening.

Other Factors:

Low signal levels overnight.

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

Summary of Stacks & Quality

Freq Unedited Edited Unedited Edited

Num Stacks Stacks Quality Quality

1 2141 1790 .703 .712

2 2141 1662 .746 .773

3 2144 1728 .684 .724

4 2144 1664 .645 .654

5 36797 17901 .612 .635

6 36797 17901 .596 .609

7 18380 9571 .424 .394

8 18380 8947 .338 .302

9 9171 5071 .202 .162

10 9171 4239 .121 .101

11 4467 2409 .049 .037

12 4593 2553 .027 .024

13 2248 1456 .019 .015

14 2188 276 .020 .017

15 1018 126 .016 .023

16 1084 982 .019 .019

17 529 255 .024 .035

18 555 495 .024 .024

19 486 204 .015 .020

20 594 132 .017 .035

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

\>=DEFINEMEAS

MAXCHAN=16

MAXRUN=999

MAXMEAS=9999

UNITS=M

REFTYPE=CART

REFLOC=DEMO88-107

REFLAT=+30:20:00

REFLONG=-122:20:00

REFELEV=200

\>HMEAS ID=1011.001 CHTYPE=HX X=75136 Y=34949 Z=153

AZM=-55 ACQCHAN=CH1 SENSOR=COIL238

\>HMEAS ID=1012.001 CHTYPE=HY X=75136 Y=34949 Z=153

AZM=+35 ACQCHAN=CH2 SENSOR=COIL239

\>HMEAS ID=1013.001 CHTYPE=HZ X=75136 Y=34949 Z=153

AZM=0 ACQCHAN=CH3 SENSOR=LOOP333

\>EMEAS ID=1014.001 CHTYPE=EX X=75087 Y=35019 Z=153

X2=75185 Y2=34879 Z2=153 ACQCHAN=CH4

\>EMEAS ID=1015.001 CHTYPE=EY X=75057 Y=34894 Z=153

X2=75214 Y2=35004 Z2=153 ACQCHAN=CH5

\>HMEAS ID=1021.001 CHTYPE=HX X=46446 Y=19773 Z=198

AZM=+25 ACQCHAN=CH6 SENSOR=COIL431

\>HMEAS ID=1022.001 CHTYPE=HY X=46446 Y=19773 Z=198

AZM=+115 ACQCHAN=CH7 SENSOR=COIL309

\>HMEAS ID=1023.001 CHTYPE=HZ X=46446 Y=19773 Z=198

AZM=0 ACQCHAN=CH8 SENSOR=LOOP334

\>EMEAS ID=1024.001 CHTYPE=EX X=46377 Y=19741 Z=198

X2=46514 Y2=19806 Z2=198 ACQCHAN=CH9

\>EMEAS ID=1025.001 CHTYPE=EY X=46477 Y=19706 Z=198

X2=46414 Y2=19841 Z2=198 ACQCHAN=CH10

\>=SPECTRASECT

SECTID=DEMO88-101

NCHAN=7

NFREQ=20

MAXBLKS=20

// 7

1011.001

1012.001

1013.001

1014.001

1015.001

1021.001

1022.001

\>SPECTRA FREQ=1.200E+01 ROTSPEC=0 BW=3.000E+00 AVGT=1790 // 49

4.52746406E-07 -1.71115211E-08 -4.42694681E-09 -7.01830118E-07
-7.73957981E-06

4.36456673E-07 4.56306566E-08 -1.71640231E-08 3.09438576E-07
6.37708419E-09

5.58939155E-06 1.00488244E-07 -7.48501421E-08 2.94604973E-07
9.91281368E-09

-4.22392699E-09 4.54804372E-09 1.92081714E-07 2.60549939E-07
-5.23433918E-09

5.64745140E-09 -3.90451675E-07 -5.53199288E-06 -3.02203738E-08
2.29023019E-04

1.34846514E-05 -1.73114984E-06 5.54458347E-06 7.99348345E-06
-6.29705312E-07

9.80942403E-08 -1.50524220E-05 2.96675542E-04 -7.65985715E-06
-1.02632714E-06

6.35002273E-09 1.61508531E-08 -1.04411191E-08 -6.46046090E-07
-8.08830464E-06

4.63793072E-07 -1.66884728E-08 -1.53994471E-08 -6.14327131E-11
2.58307442E-09

5.55394899E-06 -6.18846400E-07 -1.38529446E-08 3.19988573E-07

\>SPECTRA FREQ=9.000E+00 ROTSPEC=0 BW=3.000E+00 AVGT=1662 // 49

8.40333598E-07 -5.90497002E-08 -1.28643396E-09 -1.31842410E-06
-1.25737060E-05

8.33283877E-07 7.29381853E-08 -4.26344116E-08 3.73151465E-07
4.45310144E-09

5.74739670E-06 4.80741733E-07 -1.26752397E-07 3.49300194E-07
1.62417102E-08

-5.26743404E-09 3.67327790E-09 1.58929055E-07 2.88102342E-07
-1.92381333E-09

4.79557372E-09 -3.85147274E-07 -5.73280886E-06 9.53154444E-09
2.43009825E-04

3.84140585E-05 -2.39897349E-06 5.54325516E-06 1.32520308E-05
-1.59949400E-06

2.37432232E-07 -2.61155456E-05 4.20059543E-04 -1.27191088E-05
-1.31608965E-06

8.18305368E-10 4.41115802E-08 -1.72784773E-08 -6.55260465E-07
-1.33560316E-05

8.69609153E-07 -1.08919418E-09 -2.90511597E-08 2.48378407E-09
2.83953505E-09

5.65893379E-06 -7.75255387E-07 -2.92501596E-08 3.76086462E-07

**...**

\>SPECTRA FREQ=2.344E-02 ROTSPEC=0 BW=5.859E-03 AVGT=204 // 49

8.18304494E-02 -8.07959586E-03 3.65992822E-03 -2.54557412E-02
-2.72234846E-02

6.64452538E-02 -2.81977956E-03 -7.00906664E-03 2.91188397E-02
1.59506081E-03

1.56243229E-02 4.81680315E-03 -1.88034959E-02 1.26437377E-02
-1.22750457E-02

3.17026186E-03 2.85452548E-02 -2.35031545E-03 -1.37817459E-02
3.14768730E-03

1.65594229E-03 1.66836232E-02 -2.13960931E-02 -2.43494939E-03
1.30557463E-01

6.02884181E-02 -2.88852323E-02 9.78550967E-03 6.44395128E-02
-2.19918098E-02

-2.43755570E-03 -1.25995213E-02 1.59109443E-01 -3.01255900E-02
-1.34579442E-03

1.22129649E-03 5.99974720E-03 1.30403582E-02 -2.38354411E-02
-6.71192259E-02

6.96095154E-02 -5.76109672E-03 -6.10302202E-03 3.15448997E-04
-7.73830281E-04

1.34903351E-02 9.67766996E-03 -5.28967381E-03 1.13396132E-02

\>SPECTRA FREQ=1.758E-02 ROTSPEC=0 BW=5.859E-03 AVGT=132 // 49

1.65410206E-01 -5.43532297E-02 9.76771815E-04 -4.04219851E-02
-7.53466859E-02

1.68768689E-01 -2.39050537E-02 -3.25651094E-03 4.29706387E-02
-1.67361286E-03

3.14700343E-02 2.24619899E-02 -5.83261587E-02 3.09599359E-02
-1.98813751E-02

3.09545454E-03 5.29161543E-02 -1.94948050E-04 -2.02756803E-02
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\>=SPECTRASECT

SECTID=DEMO88-102

NCHAN=7

NFREQ=20

MAXBLKS=20

// 7

1021.001

1022.001

1023.001

1024.001

1025.001

1011.001

1012.001

\>SPECTRA FREQ=1.200E+01 ROTSPEC=0 BW=3.000E+00 AVGT=1184 // 49

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\>SPECTRA FREQ=9.000E+00 ROTSPEC=0 BW=3.000E+00 AVGT=1280 // 49

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2.49488812E-06 -1.30704143E-06 -3.78024900E-08 3.50467730E-07

**...**

\>SPECTRA FREQ=2.344E-02 ROTSPEC=0 BW=5.859E-03 AVGT=186 // 49

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\>SPECTRA FREQ=1.758E-02 ROTSPEC=0 BW=5.859E-03 AVGT=192 // 49

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1.25867650E-01 8.14224314E-03 -8.67272611E-04 -7.68693571E-04
-2.08270992E-03

-3.18901837E-02 -1.38553334E-02 1.62106729E-03 7.57595301E-02

\>END

# References

Aho, A.V., and Ullman, J.D., 1978, *Principles of Compiler Design*:
Addison Wesley.

Bostick, F.X., 1986, *Electromagnetic Array Profiling (EMAP)*: Expanded
Abstracts of the Technical Program of the 56th Annual International
Meeting: Society of Exploration Geophysicists, p. 60.

Eggers, D.E., 1982, *An Eigenstate Formulation of the Magnetotelluric
Impedance Tensor*: Geophysics, v. 47, p1204.

Gamble, T.D., 1978, *Remote Reference Magnetotellurics with Squids*:
Ph.D. thesis, University of California, Berkeley, LBL-8062.

Jupp, D.L.B., and Vozoff, K., On: *The Magnetotelluric Method in the
Exploration of Sedimentary Basins*: Geophysics, v. 41, p.325.

LaTorraca, T.R., Madden, T.R., and Korringa J, *An Analysis of the
Magnetotelluric Impedance for Three-dimensional Conductivity
Structures*: Geophysics, v 51, p 1819.

Ting, S.C., and Hohmann, G.W., 1981, *Integral Equation Modeling of
Three-dimensional Magnetotelluric Response*: Geophysics, v. 46, p 182.

Vozoff, K., 1972, *The Magnetotelluric Method in the Exploration of
Sedimentary Basins*: Geophysics, v. 37, p.98.