M RESCUE (LOCATION) 

'TEM FOR DEEP MIMES 

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HASE 11 - BUILD A 

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THE INTERN - - 

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REPORT WCUMENTATION IL RMm 1" % lkdp.cas - h 1 

.- - 

EM Rescue (~ocation) System for Deep Mines 

Phase I1 - Build and Test Breadboard Equipment 

- 

PAGE 

9 October 1984 

I I A mr nrd hbm). Ir lha~~.~. I 

404 Tasman Drive 

Sunnyvale, CA 94086 

7. hthorw 

F.B. Curry, T.C. Moore, L.H. Rorden, I.D. Schleicher 

Y. hr(omrkl. Olpnlut)or, W.m wnd *ddru 

Devel coy Inc . 

rkr(om~1-A.DL1394-841 01 5 

la W/Tnuwrcl Um WI 

1394 

IL-~-~ 

u~~o.a(~n~f100~ ABSTRACT 

U.S. Department of the Interior 

Bureau of Mines 

Washington, DC 20241 

The purpose of this program is to extend electromagnetic (EM) techniques for use in locating miners trapped in mines as deep as 1000 m. A previously 

developed EM system is considered adequate for use at mines less than 300 m 

deep where it has a probability of detection of 54%. A system for deep mines 

must keep underground equipment simple, and use extremely low frequencies 

(ELF) , sensi ti ve receivers , and noise cancel 1 ation. The proposed 1 ocation 

method, developed by Develco for other applications, is based on vector field 

measurements from two or more static sensors and computation of source location 

by i terati ve techniques . Duri ng Phase I I, very sensi ti ve search coi 1 sensors 

were built and used in a separate test to verify the feasibility of atmospheric noise cancel 1 ation. A "Breadboard" 1 ocation system version without 

cancel 1 ati on, which is a fi el dab1 e test bed to eval uate receiving and 1 ocati on 

functions, was tested and supplied. Very good results were achieved from the 

first in-mine test with the transmitter at a depth of 380 m. It is expected 

the results of this work, and additional evaluation tests in the future, will 

be used to define the requirements for a prototype operational system. 

Final 

SEP 1981 -0CT 1984 

u 

Deep mine rescue Noise cancel 1 ation 

Trapped miner location Extremely low-frequency noise 

Through-the-earth communication 

Ouasi -static magnetic fie1 ds 

bMaahm~T.nm 

=-wElectromagnetic 1 ocation methods 

Search coil sensors 

Atmospheric noise 

Approved for pub1 ic release, distribution 

unl imi ted 

ma -.la hI-mR.rm omacu-ml*Jn 

(Iomndy m- -*- 

~ncl assi fied 

2aw'mbm) 

Unclassified 

tLMo 
FOREWORD 

Thi s report was prepared by Devel co, Inc., Sunnyvale, Cal i forni a under 

Contract J0199009. This contract was i ni ti ated under the Industri a1 Hazards 

and Communications program. It was administered under the technical direction 

of the U.S. Bureau of Mines Pittsburgh Kesearcn Center with John Durkin, Harry 

Uobros~i ,and Steve Shope acti ny as successive Tecnni cal Project Ofti cers . Janice Johnson was the contract administrator for the t3ureau of Mines. This 

report is a summary of the work recently completed as a part of this contract 

during the period September 1981 - October 1984. This report was submittea by 

the authors in December 1984. 

There were no inventions or patents disclosed as a result of Work performed 

on this contract. 

We would like to thank the Kerr-McGee Chemical Corporation for permission to 

use their Hobbs Potash Facility for the in-mine tests on this program. Walter 

Case, Jr., Faci 1 i ty Manayer ; Me1 Pyeatt , General Superintendent - Underground ; 

John Philippus, Mines Engineer; and t3ill Henderson - amony others - provided 

val uable assistance for the tests. Rodger Sturgeon of Kerr-McGee, Oklahoma 

City, assisted in the planniny stage. Steve Shope of the USBM Pittsburgh 

Research Center assisted with the underground operations. We would also like 

to thank ~erb Mill-s and Calvin Walkingstick of the U.S. Geoloyical Survey for 

their permission and assistance in using the Stonecanyon Seismological 

Observatory near Hollister, California for the noise cancellation tests 

pro~ect .
CONTENTS 

Page 

Report Documentation Page ................................... 3 

1.0 Introduction ........................................... 5 

2.0 Breadboard Location System Equipment ................... 9 

2.1 Search Coi 1 Sensors .................................... 11 

2.2 Sensor Data Unit and Preamplifier ...................... 16 

2.3 Location Analysis Unit ................................. 22 

2.4 Beacon Transmitter ..................................... 26 

3.0 3-Axis Search Coil Calibration ......................... 29 

A . Method of Measuring Voltages ....................... 31 

B . Helmholtz Coil Adjustment .......................... 32 

C . Search Coil Calibration ............................ 35 

4.0 Test of Atmospheric Noise Cancellation by Using a 

Remote Sensor ...................................... 44 

4.1 Location and Set Up .................................... 44 

4.2 Data Analysis ........................................ 45 

4.3 Conclusion ........................................ 54 

5.0 In-Mine Location Test .................................. 55 

5.1 Site Description ....................................... 55 

5.2 Sensor System Installation ............................. 55 

5.3 Transmitter Installation ............................... 61 

5.4 System Functional Checkout ............................. 61 

5.5 Location Test Data ..................................... 65 

5.6 Location Results ....................................... 66 

5.7 Discussion of Results .................................. 71 

6.0 Conclusions and Recomnendations ........................ 74 

Appendix I . Summary of Method Used to Determine Power 

Spectral Density for Cancel lation Tests .............. 76 

Appendix I1 . Location Test Data Sheets ..................... 77 

References .................................................. 106 
TABLES 

Page 

Specifications . Develco Model 107310 3-Axis Search 

Coil Sensor ........................................ 12 

Specifications . Develco Model 107145-02 Data Unit ... 18 

Sensor data unit and preamp1 ifier calibration ratios .. 21 

Location analysis unit hardware ...................... 23 

Helmholtz coil transfer function calibration ......... 30 

Orthogonality measurement before adjust cross trim ... 3 7 

Fi nal orthogonal i ty measurements ..................... 38 

Total search coil and Helmholtz a1 ignment error 

after trim ......................................... 39 

Calibrated scale factor . search coil and post 

detection amplifier ................................ 41 

Post detection amplifier ............................. 42 

Scale factor referred to search coil output .......... 43 

Sumnary of cancellation results ...................... 50 

Sensor positions and aximuthal orientations .......... 59 

Transmitter parameter measurement sumnary ............ 63 

Transmi tter-1 oop parameters and moments .............. 63 

Typical measured atmospheric noise levels at 8Hz ..... 64 

Location results from in-mine field test ............. 70 

System signal-to-noise ratio vs . time ................ 72 
ILLUSTRATIONS 

Page 

2-1 Breadboard Location System ..................... 10 

2-2 3-Axis Search Coil Sensor ...................... 13 

2-3 Block Diagram . Search Coil and Post 

Detection Amplifier .......................... 14 

2-4 Search Coil Frequency Response ................. 15 

2-5 Sensor Data Unit Block Diagram ................. 17 

3-1 Cal i bration Voltage Measurements ............... 31 

3-2 Helmholtz Crosscoupling Network ................ 33 

3-3A/B Helmholtz Calibration Measurements ............. 34 

3-4 Search Coil in Test Stand ...................... 36 

4-1 Noise Data Transmission Setup .................. 46 

4-2 Noise Data Receiving and Recording Setup ....... 47 

4-3 Relative Gain .................................. 48 

4-4 Typical Spectral Display for a Horizontal Coil 

A . Individual Coil . Remote Site ............ 51 

B . Noise Residue after Cancelling ........... 51 

4-5 Typical Spectral Display for Vertical Coils 

A . Local Site ............................... 52 

B . Remote Site ............................. 52 

4-6 Comparison of Results with Theoretical Noise 

Limit ........................................ 53 

Plan View of In-mine Test Location ............. 3-Axis Search Coil Surface Sensor Measures 

Signals from Transmi tter-Loop in Mine ........ Sensor Data Unit Processes Signals and 

Displays Amp1 i tude and Phase Information ..... Equipment Van Holds (left to right) Computer 

System. Sensor Data Units. and Tape Recorder .. Computer Calculates Transmitter Location Based 

on Information from the 3 Sensor Data Units ... Location Results from In-mi ne Field Test ....... Location Results from Data Sets 1-6 ............. Location Results from Data Sets 12 and 13 ...... Location Results from Data Sets 15-20 .......... 
1.0 INTROUUCTION 

The primary objective of this program is to extend electromagnetic (EM) 

techniques for use in locating miners trapped in deep mines through 1,000 m 

of overburden with bulk conductivities less that 0.01 Siemenslmeter. In 

terms of signal energy, for a given practical underground transmitter size, 

this problem is on the order of 1,000 times more difficult - in regard to 

accuracies on the order of 1% - than has been demonstrated to date in 

shallower mines less than 300 m deep. 

The U.S. Bureau of Mines has sponsored the development and testing of a 

VF (kHz frequencies) electromagnetic system for detection and location of 

miners trapped underground, which is considered adequate for use at those 

mines less that 300 m deepo1 Recent field studies of this system in coal 

mines throughout the United States have shown that the probability of 

detecting a miner's signal from depths of 150 m and 300 m is about 95% and 

54%, respecti velyO2 

In the existing VF system approach the miner carries a small beacon 

transmitter that is powered for two to four days by a cap-lamp battery when 

operated in a pulse square wave mode (10% duty cycle). In the event of an 

emergency the miner depl-oys the transmitter's antenna, which consists of 

300 feet (91 m) of 18-gauge copper wire, in as large a horizontal loop as 

possible. When the transmitter is turned on, the loop produces a 

quasistatic magnetic field similar in shape to the field from a nominally 

vertical bar magnet. A portable surface receiver and single axis loop 

antenna is used to locate the surface point approximately over the 

transmitter by searching for the horizontal maynetic field null which is 

located at a point perpendicular to the plane of the loop. 

In order to conduct similar location operations in deeper mines, which 

comprise about 10% of the coal mines in the U.S. and have 20% of the 

miners, or to increase detection in the shallow mines, improvements are 

necessary. 

During Phase I of this contract, the requirements for successful 

operation in deep mines were considered and various alternatives for 

transmitters, sensors, receivers, noise processing and determination of 

1 ocation were eval uated. 

There are practical physical limits on the size of transmitting antenna 

that can be conveniently carried, deployed in confined ci rcumstances, 

energized in an intrinsically safe manner and used for accurate location. 

Thus it appears that the sizes of portable transmitter and antennas 

developed to date are close to optimum. Further gains in beacon 

performance will only be made by a combination of larger antenna wire, 

lighter conductor material, high efficiency transmitters and better 

batteries. Moderate increases in signal strength and in battery capacity 

can be achieved. 
The key problem to be solved is the difficult one of detecting very small 

signals in the presence of high noise levels and obtaining enough 

information to accurately locate the beacons under difficult emergency 

conditions. 

Advanced communication techniques such as impulsive noise processing, 

continuous (cw) signalling, and coherent detection methods must be 

utilized. Also, long-term integration (up to an hour or more in some 

cases) of the signal is essential to provide the accurate measurements 

needed to determine location of the transmitter. Most of the sophistication must be built into the surface receivers, using microprocessors for 

automatic processing, in Order to keep the transmitters low cost and light 

wei ght . The need for the strongest practical signal and continuous operation 

during the receiving process is essential for detection, but will 

considerably reduce battery life (by 112 to 114) compared with that 

obtained in the present system. The reduction can be minimized by using 

the techniques indicated above. The tradeoff of battery life versus signal 

strength should be considered in the future. 

A precise, very low noise (high sensitivity) magnetic field sensor is the 

most important system component. The only two choices currently available 

that can approach the requi red sensi ti vity are cryogenic superconducting 

detectors (SQUID'S) and search coils (induction coils). The cryogenic 

detectors require liquid helium, among other drawbacks, which is 

inappropriate for this type of field application. Using techniques 

developed by Develco, compact portable search coils with sensitivities 

better than SQUID'S at frequencies above a few hertz have been designed for 

general field use. 

The sensor must be stationary to prevent even very low-level 

vibration-induced rotations in the earth's magnetic field from inducing 

additional electrical interference in the signal band. Because of this 

stability requirement and the considerable time that may be needed for 

accurate si9nal measurement, a physical search for signal minimums is not 

feasible. Therefore, it is necessary to make vector field measurements 

with 3-axis sensors at two or more (depending on the geometry of the 

problem) known surface 1 ocations; i terati ve computational techniques are 

used to solve4for the source location as Develco has done in previous 

applications. This is quite an involved process but can be automated in 

pract i cal field equi pment . Operation at frequencies between one and 10 Hz is dictated to optimize 

system performance as a function of noise, propagation and field scattering 

effects. At these frequencies, a practical transmitter at depths greater 

than 400 meters or so produce% signal levels at the surface that are on the 

same order as, or less than, the natural atmospheric noise levels. Thus, 

some form of spatial or spectral noise cancellation technique is essential 

for si ynal detection and measurement at the deeper mines. (A 10 d8 
reduction of noise reduces location time by a factor of 10.) Cancel lation 

by using a remote sensor to sample essentially pure noise to be subtracted 

from the contaminated si gnal has been selected for ini t i a1 eval uat i on 

since there is5some evidence it does work, at least in some 

ci rcumstances . There are two key areas that have not been addressed in detail to date 

because of a lack of data. Man-made noise at frequencies below 20 Hz 

(such as power1 ine switching transients) can be expected to be si ynificant 

in some instances and may predominate after application of cancellation 

and processing. Propagation effects such as multipath signals, or 

scattering from conducting and magnetic inhomogeneities can result in 

significant signal errors. There is limited in-mine experience6 that 

suggests scattering is not a serious problem at low frequencies, but this 

must be checked under conditions more representati ve of thi s appl i cati on . Extensive field experience is needed to determine if these potential 

problems do have a si gni ficant effect on system operation and, if so, what 

the best solutions are. 

The objective of the recently completed Phase II contract work was to 

construct a "breadboardn 1 ocati on system and conduct prel i mi nary tests 

with it. This preliminary system is a fietdable test bed to evaluate the 

recei vi ng and 1 ocati ny functions and to col 1 ect addi ti onal data. The 

primary Phase I1 test goals were to verify the sensor sensitivity, noise 

cancel lati on (in a separate test), noise processing, and location method 

operation (including in a mining environment). It is expected the Bureau 

wi 11 conduct additional tests at a number of other mines in order to 

evaluate the system under various conditions and, ultimately, define the 

requi rements for a prototype operational system. 

Four triaxial search coi 1 sensors were built and tested to verify the 

required sensitivity and accuracy could be achieved. The first two were 

used in a preliminary long baseline (5-10 km) noise cancellation 

experiment to confirm feasibility and determine how (and whether) to 

implement cancellation in a fully operational prototype system. In 

general, three sensors will be used in a triangular array, with a spacing 

on the same order as the transmitter depth to provide resolution and area 

coverage. A three-sensor co-linear array, which may be useful for some 

mine or terrain situations, was used for the in-mine test. The fourth 

sensor will be used for additional cancellation tests in the future. 

-- (SUU~ -used in an EM navi yati on system orincorporate automatic si ynal processing, ' 

Fin this application. r 

calculations for the preliminary fiei 

locat i on software developed by Devel cl 

manually in this system version. 

852-1476} 

- 

to peformtne location 

ii using the copyrighted 

ata entry is accompli ,bed 

, RGI P/N . .'or the . _ ,ation 
tests, but there was no attempt to improve their efficiency. Finally, an 

in-mine test was conducted at moderate depths (approximately 400 m) to 

evaluate the system operation under nominal conditions without the added 

complexity of noise cancel lation in this initial test phase. 

This report discusses the Phase I1 work with emphasis on the test 

results . 
2.0 BREAOBOARO LOCATION SYSTEM EQUIPMENT 

The "Breadboard" system components, shown in Figure 2-1, were used to 

test key functions of the location method concept that had been proposed 

for use in deep mines (up to 1 km depth), in order to complete1 y speci fy 

the design requirements for an operational prototype version of the EM 

Rescue Sys tem. 

* The si ynals for the system are generated by an underground beacon 

transmitter, with a 300-foot (or yreater) circumference loop antenna laid 

out in an approximately horizontal plane. This produces a low frequency 

dlternating magnetic field equivalent to that of a nearly vertical magnetic 

dipole perpendicular to the plane of the loop. The field is quasi -static, 

i.e., nonradiatiny, and decays rapidly with distance from the transmitter. 

A version of the present miner location VF transmitter was modified to 

produce low frequency si gnal s for the "Breadboard' system tests. Since 

this transmitter version is unregulated, it was powered by two cap-lamp 

batteries in parallel to achieve better amplitude stability and lonyer 

operational time for the purpose of the tests. 

The "Breadboard" EM location system uses an array of three triaxial 

sensors on the surface to make vector field measurements of the siynals 

produced by the transmitter. They are set up in known positions and 

orientations that are in the general area nearly over the probable 

transmitter location. The array pattern may be either linear or, more 

yenerally, triangular (depending on the mine configuration) with a spacing 

between sensors and maximum offset of the array on the order of the depth 

to the transmitter. (Lateral offset of a linear array should be less.) 

The plane (or 1 ine) containing the sensors (or loop antenna) does not have 

to be level ,but severe tilts may require operator assistance to achieve the 

correct 1 ocati on. 

Three sensors will often be sufficient for use at mines on the order of 

300 to 400 m deep, which was the goal for preliminary tests of the 

"Breadboard" system location (only) functions. At mines up to 1,000 m in 

depth, an additional sensor is required for noise cancellation in 

operational systems. This results from the fact that natural atmospheric 

noise levels, at the low operating frequencies required to minimize the 

effects of earth conductivity, are very high compared to the weak surface 

signals from transmitters at the greater depths. Under these conditions, 

the time required for si ynal integration to achieve a suitable 

signal -to-noi se ratio (SNR) for accurate location is unacceptable. Since 

the propagating atmospheric noise fields change slowly over reasonably 

uniform earth, it is possible to coherently cancel most of the noise at the 

local sensors by sensing noise only at a remote location. A separate test 

of this method was conducted as described in Section 4. 

The search coil sensors used in the "Breadboard" system tests have an 

intrinsic system noise level sliyhtly lower than the expected atmospheric 

noise cancellation levels. The goal is to be able to achieve a 40- 

to 60-dB SNR with a signal integration time of an hour or less although 

longer times may be required under poorer conditions or to achieve greater 

accuracy. Each of the three sensors used for location are connected by a 

cable to a Sensor Data Unit for automatic detection of the signals and 

preprocessing of the data. The Location Analysis Unit (LAU) processes the 

measurements from the SDU's and solves for the most likely location of the 

transmitter. 

SEARCH COIL SENSORS 

The Model 107310 triaxial search coil specifications are given in Table 

2-1 and the overall dimensions are shown in Figure 2-2. The search coils 

have the hi gh degree of sensitivity and accuracy required for accurate 

location work in a relatively compact form. It is possible to break the 

structure down to elements that are easy to transport and then reassemble 

quickly and accurately at any requi red location. 

Each axis of the array consists of a copper wire solenoid wound around a 

highly permeable core and is electrostatically shielded. The solenoid is 

encapsulated in a fiberglass tube which can be accurately and reproduceably 

aligned. The three rods required for a complete vector field measurement 

sensor, are held by screw clamps in a central hub. The rods are 

sufficiently rigid so that accurate alignment can be maintained without the 

need for additional struts between the ends. 

In order to minimize the profile, the lower end of the vertical rod can 

be inserted in a hole, when ci rcumstances permit. A ri gi d supporting 

structure can be used on hard surfaces. Mounting feet with adjustable 

screws are clamped on the ends of the horizontal rods for leveling the 

structure by using a precision bubble level mounted on the hub. The unit 

is rou hly aligned in the preferred direction. A transit or portable laser 

level 9 construction type) is used to precisely determine azimuth by 

si yhting on an optical mirror, mounted on the hub, and measuring the 

reflection anyle. A secure, noncontacting wind screen must be placed over 

the sensor to minimize mechanical vibration. 

The electronics block diagram for the search coil is shown in 

Figure 2-3. The preamplifier and feedback circuit bui 1 t into each coi 1 rod 

provide a flat frequency response from approximately 0.2 Hz to 200 Hz. The 

preamplifier front end utilizes low noise FET's selected for a noise 

voltage density of approximately 5 n~/m. The overall effective noise 

level of each axis of the search coi 1 is equivalent to -156 dB Ho (or Hno = 

15.9 x 10~~ ~lmlm) at 10 Hz and varies approximately inversely with 

frequency . A separate, so-cal 1 ed post detection amp1 i f i er provides additional gain , notch filtering for powerline interference, and orthogonality trimning for 

the 3-axis search coil assembly. It is placed close to the coil assembly 

to minimize possible noise pickup on the coil output lines. In the simple 

version used for the "breadboardH system tests (Figure 2-3), 
Intrinsic Noise Level -153 dBHo* at 10 Hz (varies approximately 

as llf) 

Scale Factor 20 V/A/m (Nominal. Calibrated to an 

accuracy of approximately +0.1%) 

Maximum Linear Output Voltage f5 V peak 

Bandwi th 

Orthogonality 

Approximately 0.2 to 200 Hz (before 60 Hz 

notch filter) 

<O.1° (calibrated with correction in 

hardware) 

Power Supply Eight AA-size batteries (12 V) 

Size 1-318 inch OD x 34 inches (each axis) 

Weight Search Coil 21 pounds; Amplifier 2 pounds 

Operating Temperature 

.dBH,is relative to 1 ~~/m~~z. 

-40°C to +60 OC (design goal ) ; (-40" F to 

+140° F) 

Tab1 e 2-1. Speci f i cat i ons - Devel co Model 107310 3-Axi s 

Search Coil Sensor (with Model 107315 Post Detection 

Amplifier) 
z 

Axi s 

X 

Axi s 

3-Axis Search Coil Sensor 

FIGURE 2-2 
I 

~TRIAXIAL SEARCH COIL ASSEMBLY I POST DETECTION AMPLIFIER I 

L -,,,,- - ---- 1 L ,,,,,,,--- ----J 

r--------- --7 r-------- 

---- - FRE-NOTCH 7 

I I I MONITOR I 

I I I 

Block Diagram 

Search Coil and Post Detection Amplifier 

FEED 

I BACK I 

I COIL I GAIN=5 

I I 

FIGURE 2-3 

I 

I 

I 

X AXIS I SENSE 

( COIL I 

I I I I I I Y AXIS I -1, , - , , , 

I I I 

i I I 

I I 

Z AXIS I I 

--- - --- I 

1 I I 

I I I 

1 I I 

I I I I 

I 

CROSS 

COUPLI NG 

NETWORK 

- - 60 HZ 

NOTCH 

I 

I > . I 

I 

I 

-- --- A I 

I 

I 

------ w 

I 

I 

I 

the gain ratio was limited to five to minimize the possibi 1 ity of 

saturation in high level powerline fields such as in the lab and 

calibration tests. Also, a single 60-Hz notch filter with an attenuation 

of approximately 35 to 40 dB was used. 

The overall frequency response of a typical search coil and post 

detection amplifier channel is shown in Figure 2-4. The amplifier outputs 

are transmitted to the receiver over a 22-gauge, three twisted shielded 

pair, 1,000 foot cable. 

Because the triaxial search coil structure is inherently asymnetrical, 

there is some magnetic coupling between the axes. To achieve better than 

0.1 degree orthogonality, this coupling must be carefully "trimned" out on 

each unit, during the calibration process. This is done with an adjustable 

resistor network that supplies a small sample of signal from each axis to 

be subtracted from each of its transverse axes to cancel the coupling. 

Thus, each post detection amplifier is matched to a particular search coil 

assembly set. If, in the future, it is found that 114 degree (or so) 

orthogonality is adequate, then it appears that no adjustment will be 

requi red. 

2.2 SENSOR DATA UNIT AND PREAMPLIFIER 

The Sensor Data Unit (SDU) , Model 107145-02, and its associated 

Preamplifier, Model 107096, were modified to serve as the signal receivers 

in the "Breadboard" location system. These units are part of a Develco 

proprietary electromagnetic guidance system for horizontal boriny. Their 

basic function is to provide wideband filtering, automatic gain control and 

di gi tal conversion, in hardware; and impul si ve noi se processing, narrowband fi 1 teri ng, coherent signal detection and phase tracking, in software. 

The modifications for the location tests consist of minor preamplifier 

changes and the addition of a "Synch" function, to measure relative phase 

of the three SDU8s, a block averaging function for long-term inteyration of 

the signal, and display of the detected field amplitudes. The nominal 

specifications and block diagram of functions are shown in Table 2-2 and 

Fi gure 2-5, respect i vel y . The combination of the external preamplifier and internal signal 

conditioner board provide an overall 3 dB bandwidth of from approximately 

1-112 to 20 Hz, for anti-alias filtering and powerline frequency 

rejection. The input of the preamplifier was modified to provide a unity 

gain differential amplifier for rejecting comnon-mode pickup on the 

1,000-foot cable to the sensor and its post detection amplifier. Notch 

filters were also added to reject the third harmonic of a square wave 

signal to prevent generation of very low beat frequencies in the impulsive 

noise limiting process. These beat frequencies are due to transmitter and 

SDU clock frequency differences and would adversely affect the long-term 

averaging process. Both the preamplifier and the signal conditioner have a 

programable gain control of either unity or 128 (2 ), which is 

automatically selected by the microprocessr unit (MPU). 
Gain Control 

h 1 I I Gain Control I 

I Convert Command 

X ' t , Track & , Central 

Processox 

(MPU) 

&I 

I/O 

Functions 

Hold Command 

Y I Signal Yo' Hold MultiZ~ Condit - Z* 

W ioner 

Gain 

+ 1 J28 

Search 

Coil 

X,Y,z 

' 

ttt 

4 

Gain Control 

Preamplifier 

Gain 

1,128 

+ 111 

Internal 

115V AC - Battery Battery , m Power Charger @ 12V Convertex 

7.5 A-H 

A 

External 

12v 

Battery 

"Snych" 

Lines 

Sensor Data Unit Block Diagram 

FIGURE 2-5 
Operatiny Frequency* 10-213 Hz 

Frequency Stability '100 ppm over the temperature range 

Analog Bandwidth Approximately 1-112 to 20 Hz 

Powerline Frequency Rejection '80 dB at 60 Hz 

>65 dB at 120 Hz 

>70 dB at 180 Hz 

Input Vol taye 

Total Variable Gain 

*5 V max. 

1 to 2*l (126 dB) max. 

Gain Calibration '0.1% 

0 

Phase Tracki ny 12 

(Channel-to-channel at signal 

frequency ) 

Noise Level <-I60 dBHo 

(Referred to preamplifier input) 

AID Converter 12 bit, +5 V full scale 

Track and Hold <2-112 US 

Si ynal Input Channel s 3 

Power Supply 115 V or 220 V, 50160 Hz (<50 W max) 

or 12 V internal battery (<4 hour operation) or 12 V external battery 

Operati ny Temperature -20 to +6U°C 

SDU PREAMP 

Size 13.5" Up x 20" W x 19"H 3-118" W x 2-114" H x 6-718" L 

(transit case) 

Weight Approx. 55 lbs. 2 lbs. 

*Default value. May also be proyrammed to operate at 2-213 and 5-113 Hz. A 

preamplifier notch filter change is also needed for satisfactory long-term 

integration with square wave signals .) 

Table 2-2. Specifications - Develco Model 107145-02 Sensor 

Data Unit (with Model 107096 Preamplifier) 
The software is written to accomodate four discrete si gnal frequencies, 

but only two are useful in this version because of preamplifier hardware 

limitations. The default operating value stored in memory (PROM) is 10-213 

Hz and the system will automatically operate at this frequency when turned 

on. An operating frequency of 5-1/3 Hz may be entered by the SDU key pad. 

The operating frequency is derived from the MPU crystal oscillator which 

has a stabi 1 ity of +lo0 ppm over the temperature range. 

Data sampling by the Analog-to-Digital (AID) board functions is a1 so 

controlled by the MPU software. Each of the three search coil axis 

channels are connected to individual track-and-hold circuits ; these are 

directly controlled by the nonmaskable interrupt (NMI) process and sampled 

at a 170-213 Hz rate. The signal channels are then multiplexed,,amplified 

by a 3-bit programable gain amplifier (PGA) with a gain from 2 throuyh 

Z7, and digitized by a 12-bit AID converter. (In addition to the signal 

data, one of nine subcomutated data channels are also sampled. Three of 

these are used for internal housekeeping functions and AID zero bias 

correction of each sample and the others are unused in this version.) AID 

conversion is not NMI controlled but occurs in the interval before the next 

channel is multiplexed. 

The signal sample data is stored along with the gain at which it was 

taken and other information for gain control. The gain of each of the 

three channels is always the same at a given time. If a gain change 

affects either the preamp or signal conditioner, one or two 1.5-second 

frames will be skipped (two for preamp) to allow for amplifier settling. 

Impulsive noise processing (INP) does not occur during the first pass of 

the routine operation. The data samples are simply sumned into the 

equivalent of a single cycle for processing to determine the initial 

estimate of the in-phase and quadrature components of the signal. Once an 

estimate of the signal amplitude and relative phase in each axis have been 

determined, each sample may then be symnetrically limited to reduce the 

effect of impulsive noise. This process consists of subtracting the 

estimated signal contribution from each sample, limiting the remainder and 

processiny the remainder for coherent signal. 

Data filtering and the second level of data processing occurs once all 

the raw data have been reduced. This process includes the computations of 

gain , fi 1 tered si gnal amplitude and phase, Si ynal -to-Noi se ratio (SNK) and 

other variables required for impulsive noise processing. The variable 

computations will differ for the nonreference and reference channels. In 

the location application, the reference channel is automatically selected 

during the initial evaluation process, based on the best SNR, and used to 

track the phase of the SDU relative to the signal. Once selected, it 

remains fixed. Prior to the selection of a reference channel, a1 1 channels 

are treated the same and use the same computations as would a reference 

channel. 
When the system is first turned on or is reset, it goes through a fast 

settling mode as part of the initial acquisition process. The required 

gain is determined by a successive approximation method starting with a 

value of 216. After testing any trial yain, the process may decide that it 

satisfies the requirements. If a ain change would set the gain outside of 

29 the hardware limitations (2 to 2 ), a warning message is displayed. 

The output from the impulsive noise limiting process is low pass filtered 

by a second-order filter with a damping factor of 0.9 and a time constant 

of 15 seconds (noise bandwidth approximately 0.01 Hz). The signal output 

of these filters is used for all other internal receiver functions. It is 

also long term integrated by a simple continuous block averaging process to 

improve the signal-to-noise ratio (SNR) of the amplitude values displayed 

for use in the location calculation. The long term averaging can be reset 

at any time without restarting the enti re signal acquisition process. 

The long-term average output amplitude is displayed in RMS pico-tesla, 

along with phase in degrees, and SNR in db for each channel on a 

40-character, electro-1 uminescent di splay. The X channel appears on the 

default line and the other lines are toggled with the key pad. Conversion 

of the SDU input voltage to equivalent field at the sensor assumes a sensor 

scale factor of 20 V/(A/M) and a post detection amplifier gain of five. 

Precise calibration ratios are applied during the location calculation 

process to achieve a more accurate result. The SDU and preamplifier set 

calibrations are given in Table 2-3. (See Section 3, Table 3-5, for the 

search coi 1 val ues .) 

The channel phases displayed are with respect to the SDU clock for the 

reference channel, and with respect to the reference channel for the other 

two channels. Ideally, the two nonreference channels will be either in 

phase (0' ) or exactly out of phase (180" ) with respect to the reference 

channel. A warning is issued if a phase anomaly greater than 3U0is 

detected (i .e., if the nonreference channels deviate more than 30° from 

being exactly In or out of phase with the reference channel). Possible 

causes of phase anomalies are electrical interference, field scattering 

from conducting structures, very low signal levels, or problems in the 

equi pment . Since the phase of each of the three SOU clocks is arbitrary, they must 

have a common reference for use in the location calculations. This is 

accomplished by a so-called "Synch" cable interconnection between the units 

to measure the phase of two secondary units with respect to a primary 

unit. The primary SDU is indicated by a shorting wire in the primary cable 

connector connected to that SDU. Each SDU polls an 1/0 port which 

indicates that the SDU is either a primary or secondary. If it is a 

primary SDU then it will cause the communications lines to the two 

secondaries to pulse every cycle of the received signal frequency (such as 

10-2/3 Hz) in synch with the primary SDU oscillator. The secondary SDU 

uses a high speed counter to start at the beginning of a signal cycle, that 
Channel X Y Z 

SDU 1 (5.3 Hz) 1 .02070 1.02070 1 .02030 

SDU 3 (5.3 Hz) 1 .02030 1 .02070 1 ,02030 

SDU 4 (5.3 Hz) 1.01300 1.01900 1.01400 

SDU 1 (10.6 Hz) 1.06870 1.06330 1.06330 

SDU 3 (10.6 Hz) 1 .06330 1 .07100 1 .06730 

SDU 4 (10.6 Hz) 1.05430 1.06100 1.05370 

Tab1 e 2-3. Sensor data unit and preamp1 i f i er cal i bration rati os 

The calibration ratio is defined as the calibrated 

B field divided by the measured B field displayed 

by the SDU. 
has been shifted to be in phase with its own clock, and count until the 

primary SDU start of cycle is detected. The phase difference between 

primary and secondary SDU is then computed and displayed in degrees by the 

secondary SDU'S. (The relative phase of the primary is necessarily zero.) 

The normal default "monitor" display registers contain five lines of 

information including the three channels of long term averaye signal data. 

They are displayed one line at a time. The X channel signal data is the 

first line displayed under all default conditions. The remaining lines may 

be displayed by pressing the "Next" key of the keypad to go in the forward 

direction only. If a warning message appears, it may be cleared by 

pressing any key, but a warning flag (letter) will remain on the right of 

the display as long as the condition exists. Other system parameters and 

data may be displayed and some may be changed by using the keypad. In some 

cases, particularly when an inadvertent parameter change could affect 

system operation, a user identification code (UIC) may be required. 

2.3 LOCATION ANALYSIS UNIT 

The Location Analysis Unit (LAU), supplied for use in the "Breadboard" 

location system, consists of a GRID Compass Model 1101 portable computer, 

with disk and printer, and Develco Locator/DLMG@ software. The key 

features of the GRID equipment are surmnarized in Table 2-4. The LAU is 

used to calculate the location of the transmitter that generates the fields 

measured by the Sensor Data Units (SDU). In the current version, data from 

the SDU's are entered manually at the LAU computer keyboard. All three LAU 

system components can be used when ac power is available, or the Compass 

1101 computer can be used alone with an optional battery pack (not 

supplied). In either case, it gives the results on site and also saves the 

input data and calculated results for future examination. 

Software supplied by GRID includes the operating system and demonstration 

programs that are stored on the hard disk and in bubble memory. The 

Develco Locator/DLMG@software is stored on the hard disk and in bubble 

memory, with a backup version on a floppy disk. The Locator software 

provides the following: 

1. Data forms that arrange the necessary inputs to the computer program 

in a convenient format. 

2. Initialization routines that synchronize, rotate and ca1 ibrate the raw 

data from the three triaxial sensor measurements to produce orthogonal 

vector measurements. 

3. Two automatic and one manual initial estimate routines that provide 

the starting point for the location calculation. 

@Copyri ghted 1984 by Devel co , Inc . 
5 Kg p0rtaDle 

320 x 24U Pixel Display 

Intel 8086 16-bit pP 

Intel 8087 80-bit Co-P 

256 K byte RAM 

384 K byte bubble 

16 K byte RUM 

30U/1200 internal modem 

GPI8 (IEEE-488) 

RS232-C/RS422 

Lithium battery clock 

110/22U V 

60 W 

10-40"~ 

I I 

8.3 Kg portable 

GRID 1101 

Compass Computer 

10 M byte Hard Disk 

(250 K bytelsec) 

384 K Dyte floppy 

(31 K byte/sec) 

GRID 2101 Epson MX-82 

Disk System Terminal Printer 

5.5 Kg portable 

GPIB Interface Board 

80 CPS 

Bi di recti onal 

9 x 9 dot matrix 

Enlarged/condensed 

Sprocket pin feed 

110 v 

100 W 

5-35"c 

A 

Table 2-4. Location analysis unit hardware. 
4. The main Locator program to calculate the source location, orientation 

and magnitude based on six convergence attempts for each initial 

estimate. 

5. A utility program to calculate fields produced by a known transmitter 

(for diagnostic purposes). 

6. A utility program for calculation of calibration data in case 

recal i brati on is necessary. 

7. Data output routines to display, store and print results in a format 

for easy eval uati on. 

Development of the location method and "Locator" software was funded by 

Develco for use in general underground and other location applications. 

The location method is based on the Develco background patent that has been 

applied for.'+ DLMG is the specific version of the "Locator" software that 

has been adapted for use in preliminary testing of the "Breadboard" 

Electromagnetic (EM) Rescue System to evaluate this method as a means of 

locating miners trapped in deep mines. There are a few minor limitations 

imposed by the specific initialization and initial estimate routines used 

in this version. It requires data from three sensor locations that can be 

at different elevations. The sensors must be leveled but the azimuthal 

orientation can be in any known direction. Best results will be obtained 

when the sensors are used in a triangular array centered over the probable 

transmitter location, with a sensor spacing on the same order as the 

transmitter depth, and the sensor or antenna plane is tilted less than 20 

to 30 degrees. In cases other than these, successful source locations can 

be made, but the starting point for the location algorithm may have to be 

entered manual ly. 

Each location project will normally have several sets of SDU measurements 

taken over time. The main project information is entered only once, 

followed by the sets of data measurements as they are recorded from the 

SDU's. All entries are made at the Compass keyboard in response to prompts 

from the Compass screen. The entered information and data are 

automatically stored on the hard disk (or in bubble memory); printed copies 

may be made if desired. All results will also be filed automatically. The 

amount of information di splayed and pri nted can be control 1 ed, i .e . , the 

output of some diagnostic technical data (which would be filed regardless) 

can be inhibited. 

Following the entry of the data into the LAU, the measurements are 

individually calibrated according to the sensors and SDU's from which they 

were recorded. The measurements are then synchronized in time using phase 

re1 ationshi ps among the sDU'S (measured with synchroni zation cables). 

Next, the measurements are mathematically rotated so that the azimuths of 

the sensors are aligned with the array coordinate system. The result of 

these preliminary calculations are vector field measurements at each 

sensor; these vectors are then used in the automatic initial estimate 

routines and in the main Locator program. 
The main location program calculates the location, orientation, and 

magni tude of a remote, unknown, 1 ow-f requency (quasi -static) mayneti c field 

source. In general, it can be used to locate virtually any magnetic dipole 

source, based on the field measurements made at three triaxial sensors set 

in a triangular array at any attitude with respect to the source. 

Depending on the geometry of the problem, it may be possible to use fewer 

sensors or other array confi gurations (e.g., co-1 inear). Given 

sufficiently accurate measurements, the program can make the correct 

location over any distance, i .e., the algorithm used is independent of 

linear scale (within the numerical limits of the computer used). 

The location program calculations employ a unique mathematical model of 

the source and the fields it produces. Six simultaneous equations are 

required to solve for the six unknowns of source position (3-X, Y, Z), 

orientation (2-tilt, azimuth), and strength (1). The computer program 

calculates the simultaneous solut4oh to the wnlinear equations by a unique 

iterative search and conuergence method. Computs;tjon begins with an 

initial estimate of Urc solution and then converges >to a correct solution 

of the equations if possible. The initial estimate does not have to be 

accurate but wst be in a suitable region that depends on the specific 

sensor array<and transmitter geometry. Because of the complex nature of 

the equations, it may not be possible to reach a solution by a given 

route. Therefore, six attempts are made for each initial estimate. 

There are multiple possible roots, or mathematically correct answers, to 

the original six equations with six unknowns. Only one is the correct 

answer to the real world problem. The nature of the equations have been 

investigated and modeled for an extensive variety of source and sensor 

configurations. Knowledge of the behavior of these functions and of the 

general constraints on possible source locations and orientations is used 

in the computer (or manual ) routines to select an appropriate starting 

point that will, in most cases, lead to the correct solution. 

A very deep starting point is generally best in the trapped miner case, 

which will usually involve locating a nearly vertical magnetic dipole 

source (horizontal loop antenna) by using sensors deployed in a nearly 

horizontal surface plane. The software has two routines to automatically 

select the starting point. The first routine selects a point below the 

projected intersection of the horizontal field di rections at the sensors. 

This method works well whenever the loop antenna is nearly horizontal (most 

cases)+ The second routine selects a starting point directly beneath the 

centroid of the sensor array. This is more conservative and may be useful 

when the sensor or antenna plane is severely tilted. Starting points based 

on other anformation may also be entered by the operator. From each 

starting mint the main Locator program attempts to find the solution. 
The mathematical sol ution occurs when the functions are identical ly equal 

to zero. In practice, the field measurements are contaminated by noise and 

there may be errors in the computer calculations which either result in 

long computational times or prevent achieving zero. Therefore, convergence 

limits are used to determine when the iteration process should be 

terminated. This can potentially lead to false answers that may or may not 

be close to a real root, but are not the correct answer. Various methods 

are used to discard false answers. For example, very often the incorrect 

answers are completely unrealistic or physically impossible. In other 

cases, they do not produce the correct field values when the equations are 

inverted. To help assure arrival at the correct answer, the results from 

the six convergence attempts are displayed in decending order of fit to the 

measured data, thus the first result listed is "best". 

2.4 BEACON TRANSMITTER 

This portion of the deep mine (1,000 m) location system equipment will be 

similar in form and function to that used in the existing Bureau of Mines 

VF equipment for shallower mines ( <300 m). That is, it will consist of a 

wire loop antenna deployed in a nearly horizontal configuration, and the 

electronic circuitry to drive it which may be powered by the miner's 

cap-lamp battery. The primary difference in the deep mine application are 

the need for: 

1. Lower operating frequencies ( 1 t o 10 Hz) to minimize propagation 

effects. 

2. Higher frequency and amplitude stability to permit the longer signal 

integration times required. 

3. Hi gher overall transmitter efficiency to achieve an acceptable 

operating time with a battery for continuous (CW) use. 

4. Higher intrinsically safe moment for a given range of probable loop 

area possi bi 1 i ties. 

Several conceptual a1 ternati ves for achieving the performance goals for 

deep mine applications were investigated as part of the Phase I work. 

However, it was sufficient to simply modify the existing VF rescue 

transmitter to operate at low frequencies (1-10 Hz ranye) for the purposes 

of the "Breadboard" system evaluation tests. 

The transmitters used were production prototypes manufactured by General 

Instruments Corporation, PIN 852-1476, which have optional output 

frequencies of 630, 1050, 1950 or 3030 HZ.~ This version would normally be 

carried on a belt and attached to a 4-volt (4.2 to 3.5 V charge-discharge 

range) cap-lamp battery when needed. The standard antenna is 300 feet of 

#18AWG solid copper wire withOa nominal resistance of 1.9~. The 

transmitter has a stable quartz crystal oscillator (30-50 kHz range) and a 

binary divider to yenerate the operating frequency. A decade divider is 
used to provide a 10% duty cycle for use with audio detection methods and 

to extend the battery life time to greater than 40 hours with a partially 

discharged battery (e .g., old battery at end of shift ) . Continuous (CW) 

operation may be keyed with a pushbutton switch. The antenna is driven by 

a full -wave swi tchi ng bridge that produces an unregulated square-wave 

output with a peak voltage and current proportional to the battery voltage 

and load. (The specified output current is 6 A with a 0.2fl, 100 pH load.) 

The modifications consisted of bypassing the transmitter oscillator and 

divider ci rcui try with another design to produce hardwi re selectable output 

frequencies of 2-2/3, 5-1/3 and 10-213 Hz. A watch crystal oscillator is 

used, similar to that in the original transmitter circuit, with a stability 

of one part in lo5 and frequency of 32,768 Hz. Its output is divided to 

the selected frequency and drives the antenna output through the original 

transmitter control and switching circuitry. In addition, the CW mode was 

hardwi red to be on continuously (i .e ., the keying switch was bypassed). 

The changes were accomplished by "piggy-backing" the new circuitry and by 

making appropriate wi ring changes - the original printed ci rcui t boards 

were not permanently a1 tered. 

The capacity of a standard lead-acid cap-lamp battery is on the order of 

12 to 15 ampere hours (A-H) with a standard 1-A lamp load. Under load 

conditions, the terminal voltage varies gradual ly from approximately 4 

volts, at full charge, to approximately 3-1/2 volts near cutoff. Although 

the voltage drop in the transmitter switching ci rcui t depends on voltage 

and the temperature, etc., the expected averaye transmitter current into a 

nominal 252 load, is on the order of 1.7 to 1.5 A peak square wave. Thus, 

under CW operating conditions, a fully charged battery will have an 

operating life of from approximately seven to nine hours. A partially 

discharged battery, such as an old one at the end of the shift, will have a 

useful life of approximately half that. As mentioned previously, these 

lifetimes are inadequate for an operational system and alternatives must be 

considered in the future. They are also inconvenient for the evaluation 

tests where it is expected the transmitter will be left on for extended 

periods of time. 

Tests were conducted with the modified transmitter and 252 load connected 

to a standard Wheat cap-lamp battery to verify the expected voltage decay 

rate. With a battery that was less than fully charged, it was found the 

terminal voltage on this sample decreased approximately 40 to 60 mV per 

hour initially, and approximately the same amount per half hour at later 

times. The total time to complete discharge was approximately six hours 

and the decay rate accelerated in the last 1.5 hours. For a simple long 

term signal averaging scheme, such as is the case for the "Breadboard" 

receiver, these fi yures translate to an equivalent signal -to-noise ratio 

(SNR) of about 40 to 36 dB, respectively, when integrated over the same 

period of time. 
Even though the signal amplitude may be changing, the receivers will 

provide the correct relative mean si ynal amplitude over a given period of 

time because the variation is common to a1 1 of them. However, the apparent 

SNR will be lower than it might otherwise be with a stable signal which 

makes it difficult to evaluate signal qua1 ity with the "Breadboard" 

system. Because of this, and the need to achieve a longer operating time, 

capacity was increased by using two cap-lamp batteries in parallel for the 

first in-mine test. 

Loop current variations caused by temperature-induced changes in loop 

resistivity (0.4% per degree C for copper) are also possible. However, 

this is not expected to be a serious factor in most test situations because 

of the fairly stable mine environment. 

The standard 300-foot wire loop antenna is to be deployed as a single 

turn around a 60- by 90-foot pillar for the in-mine test. The enclosed 

area is 5,400 square feet (502 m ) . This antenna conf i guration wi 11 

generate a peak magnetic dipole moment (turns X area X current) of 753 ~m~ 

with a nominal peak square wave current of 1.5 A. The RMS moment referred 

to the fundamental frequency is 2J2 Ill times the peak square-wave value or 

678 Am 2. 

If the standard antenna is layed out in a one-turn square configuration 

(the largest probable size in actual mine installations), the enclosed area 

wi 11 be 523 m and the inductance wi 11 be 190~ H. If the peak energy 

storaye (112 LI~) is limited to a conservative intrinsically safe level of 

112 millijoule (mJ), then the peak current must be limited to 2.3 A, with 

square wave excitation. The VF transmitter output will typically be less 

than this when used with the 4-1 battery (4.2 maximum less transmitter 

voltage drop) and 1.9~(nominal at room temperature) antenna. 

A larger loop antenna was also used for the first in-mine test to 

simplify initial system functional checkout. The wire was 1,000 feet of 

#14AWG copper wire with a nominal resistance of 2.5n. It was wrapped 

around four pillar~~with a total enclosed area of approximately 52,900 

square feet (4915 m ). A fundamental frequency RMS moment of approximately 

6600 Am was expected to result if a peak current of 1.5 A was achieved. 
3.0 3-AXIS SEARCH COIL CALIBRATION 

Four 3-axis search coi 1 assemblies were calibrated at the NASA-Ames 

6 Research Center Magnetic Test Faci 1 i ty . The 20-foot diameter, 3-axi s 

Helmholtz coil facility was used in order to have minimum gradients. 

Although it is usually used for dc measurements, the Helmholtz coil support 

structure is insulated to prevent eddy currents at ac. (A large 

demagnetizing coil structure approximately 30 feet south from the Helmholtz 

center was not insulated, but it did not produce any significant effects.) 

All measurements except those for the Helmholtz coil transfer function were 

made at 5 Hz. Measurement and performance yoals were: 

a) Helmholtz gradients <0.1% within - +15 inches of center. 

b) Anyular measurement accuracy <+1 - m radian (+0.1 - mr goal ) . 

c) Search coil orthogonality<+l - m radian (0.057 degrees). 

d) Search coil scale factor accuracy < '0.1%. 

The Helmholtz coil gradients at 5 Hz were measured and found to be 

less than 0.14% over a reyion'of 224 inches about the center. (The N-S 

axis had the maximum gradient. The E-W gradient was much less and the 

vertical gradient was negligible.) The transfer function of each Helmholtz 

coi 1 pai r (verti cal , East -West, North-South) was preci sely cal i brated at dc 

by switching polarity with the results shown in Table 3-1. 

The fields produced by the respective Helmholtz coil pairs were adjusted 

to be level (or vertical ) and mutually perpendicular by means of a cross 

coupling network. A precision level was used to establish the horizontal 

plane. A visible laser source, located approximately 45 feet from the coi 1 

center and oriented parallel to the N-S axis, and an optical (reflecting) 

block were used to establish a repeatable reference axis and permit precise 

90-degree rotations. 

The 3-axis search coil assembly shown in Figure 2-2 includes a precise 

bubble level and front surface mirror for orientation with respect to 

vertical and azimuth (the laser line). Since the Helmholtz field 

directions were precisely adjusted, it was sufficient to leave the search 

coil orientation fixed and sequentially energize the Helmholtz coil pairs. 

The search coil X, Y, and Z axes were oriented parallel to the Helmholtz 

E-W, N-S (the laser line) and vertical axes, respectively. 

The output of the search coil parallel to the field is proportional to 

its scale factor. The output of the search coils' transverse to the field 

is proportional to their orthogonality with respect to the first search 

coil. Orthogonality was electrically adjusted by means of a cross trimning 

network in the post detectionoamplifier to achieve a minimum output from 

the transverse search coils. 

Detai 1 s of the Helmhol tz coi 1 orthogonal i ty adjustment and search coi 1 

calibration procedures are described in the following: 
Axi s TH (GausslAmpere) 

X (E-W) 0.4464 

Y (N-S) 0.4271 

Z (vertical) 0.5748 

Table 3-1. Helmholtz coil transfer function cal i bration. 

Averaged for gradient over 40 cm about the 

centroid. 
A- METHOD OF MEASURING VOLTAGES 

The voltage measurement setups used are shown in Figure 3-1. 

TMB = lmS,200 points (>1/2cycle

TRIG = ext, normal, DC 

INP = DC coupled, f500mv 

Wave Form 

Analyzer 

Low Pass Filter 

Search 

Coils Low Pass Filter 

Sensor 

DATA 

6000 * 

Same Settings 

INP = DC, f5V 

Stacked from 20 to 100 samples 

ext trig 

I 

Magnetometer 

box 

Same Settings 

' ' 

10 Hz 

Gain=l 

(0 dB) 

> 

Post 

.Detection 

Gain=5 

DATA 

6000 * 

Helmholtz 

Coil - 

INP = DC, 45V or 450V 

(Use scope for preliminary 

Helmholtz adjustment.) 

7 

10 Hz 

Gain = 10 

(20 dB) 

. - 

ext trig I I 

FIGURE 3-1. Calibration Voltage Measurements 

i 

ext trig Current , 

2K 

DATA 

6000 

• 
8.HELMHOLTZ COIL AUJUSTMENTS 

1) The cross coupliny network that was Used to trim the Helmholtz 

coil aliynment is shown in Figure 3-2. Connections to the 

Helmholtz coils are also shown. 

2) A glass plate (1) was placed in the center of the coil structure 

as shown in Fiyure 3-3A. 

3) The plate (1) was then leveled using a precision and sensitive 

level that was placed in the center of the plate. 

4) A fluxyate maynetometer (2) was firmly attached to a square, 

mirror-coated gl ass pri sm (3). 

5) With the vertical coil energized (rotary switch S1 in Figure 3-2 

in position 3) with the maximum available current (about 20 V p-p 

at the generator output), P3 was adjusted to give the same 

magnetometer reading (amplitude and phase) when its axis pointed 

E or W. P6 was adjusted to give the same reading when its axis 

pointed N or S. At this point, the vertical field was perpendicular to the leveled plate with an estimated 0.5 m Radian 

accuracy. 

6) The glass prism was rotated into a position in which the fluxyate 

axis is vertical. See Fiyure 3-3B. With the fluxyate in the 

position shown in Figure 3-3B and the N-S coil energized (S1 in 

position 2) the field reading is equal in amplitude and reversed 

in phase to the reading obtained after the prism is rotated 180 

deyrees. This is achieved by adjusting P8. The same procedure 

is repeated with the E-W coil eneryized (S1 in position 1) and 

adjusting P7. At this point both E-W and N-S fields lie in a 

horizontal plane. 

The prism is brought back to its position as in Figure 3-3A. 

Nith the E-W coil eneryized and the fluxyate axis pointiny N-S, 

the prism was rotated to get the minimal output. A laser visible 

source placed on a tripod about 45 feet away was adjusted so as 

to yet the reflected beam (from the prism) anywhere above or 

below, but on a vertical line that passes through the source. 

With the laser source in this fixed position the prism can be 

rotated in precisely 90 degree steps. The fluxyate is rotated 

back and forth 180 deyrees (to point N and 5) and P4 adjusted to 

get the same amplitude and opposite phase. 

8) With the N-S coil energized and the fluxgate sensor pointiny E 

(using the laser beam for precise aliynment) the same amplitude 

and opposite phase of the measured field is adjusted using P2 and 

flipping the sensor from E to W several times for repeated 

measurements. At this point, the E-W and N-S fields are 

[ (2) Fl uxgate magnetometer (1 

ng optical 

lass plate 

Level i ng 

Instrument cab1 es 

FIGURE 3-3A 

FIGURE 3-38 

Helmholtz Calibration Measurements 
orthogonal. The procedure is complete. (As a cross check, all 

measurements can be repeated without adjustment to make sure 

previous adjustments were not affected .) 

C. SEARCH COIL CALIBRATION 

1) The search coil structure is mounted on a stand, designed to 

locate its center in the center of the Helmholtz structure, with 

level i ny and azimuth adjustments. See Fi yure 3-4. After 

leveliny, the search coil structure is rotated and aligned with 

the laser beam that is bounced off a mirror glued to the holding 

hub. 

2) Energizing one axis at a time, the outputs of the cross axis are 

adjusted to read zero (or a minimum 1 imi ted by noise). 

3) The output of the main axis is measured as well as the voltaye 

across the current monitoring resistor. 

To avoid saturating the search coil post detection amplifier (with a gain 

of five), ambient field amplitudes were limited to levels on the order of 

3U to 45 mA/m peak. The ambient noise fields (mostly 60 Hz and some 

180 Hz) were on the order of less than 2 to 5 mA/m peak. Noise levels were 

reduced to less than 0.1 mA/m peak after the post detection notch and other 

filtering. Using the Data Precision 6000 Waveform Analyzer to diyitally 

stack from 20 frames (for orthoyonality measurements) to 100 frames (for 

scale factor measurements) further reduced the noise levels to 0.03 and 

0.01 mA/m peak, respectively, i .e., 60 to 70 dl3 below the signal levels. 

The residual noise was mostly due to power line and other sources. The 

in-band noise (below 10 Hz) was approaching the atmospheric noise level 

limit after precautions were taken to minimize noise induced by vibration. 

The search coil ortnoyonality measurements before and after the 

electrical cross trim adjustments were made are summarized in Tables 3-2 

and 3-3. The "beforet1 measurements include the effects of both electrical 

(e .g . , cross coupl i ng between the asymmetrically 1 ocated individual search 

coi 1s) and mechanical (e.g., setup, mirror, level , and individual search 

coi 1 mi sal i gnments) factors. The "final " measurements were made after 

refining the test setup and procedure. Mechanical repeatabi 1 i ty (i .e., 

without making any electrical Radj ustments) was checked by taki ny apart 

two of the 3-axis search coi 1s and then reassembl in9 them and repeating the 

measurements with satisfactory results. Table 3-4 illustrates the worst 

case misalignment errors by assuminy the search coi 1 and Helmholtz coi 1 

misalignments are additive. The maximum error of 2 milliradians or 0.1 

degrees is well witnin the limit considered necessary for accurate 

location. 
FIGURE 3-4. Search Coil in Test Stand. 
Drive Axis: EW Drive (X) NS Drive (Y) Vert Drive (Z) 

Output Axis: Y Z X Z X Y 

SIN 4 5.0 3.4 3.3 1.3 2.4 0.3 

Includes measurement and procedure errors, e. . , (1) azimuth 

errors wi th 1 aser a1 ignment on 25' base1 ine; 9 2) Helmhol tz coi 1 

connection problem; and (3) voltage (pp) measurement errors due 

to noise. Procedure and setup was improved prior to the final 

measurements. 

Table 3-2. Orthogonality measurement before adjust cross trim; 

i.e., pots in "0" position. (All values in 

mill iradians.) 
a COO CU maC3 I CU cr)b\ d C3CUC3 I 

CUW ma0 . . 

00 

a 

CON 

. . 

Or 

h C*) 

V11 

00 

C3 

19 

0- 

aJ 
Worst Combined 

Drive X Y Z Axi s (RSS) 

Axis 

Reassemble X 1.44 1.18 1.44 1.86 

S/N 2 Y 1.29 1.43 1.43 1.93 

Z .70 1 .O1 1.01 1.23 

Repeat X 1.22 .54 1.22 1.33 

S/N 4 Y .63 .54 .63 .83 

Z .54 .51 .54 .74 

Reassemble X 1.30 .61 1.30 1.44 

S/N 4 Y .63 .54 .63 .83 

Z .88 .86 .88 1.23 

Worst Case 

Table 3-4. Total search coil and Helmholtz alignment error 

after trim. Values are sum of search coil and 

Helmhol tz misal ignment. (A1 1 values in mi 11 i radians. ) 
The calibrated scale factors for the search coil and post detection 

amplifier combination, as measured in the test facility, are shown in 

Table 3-5. The measured gain of the post detection amp1 ifier is shown in 

Table 3-6 and the net scale factor calculated for the search coil alone is 

shown in Table 3-7. 
Scale Factor (V/ (A/m) ) 

X Axis Y Axis Z Axis 

Unit (EM) (NS) (Vert. ) 

SIN 1 91.33 91 .40 90.87 

(mean 91.20 + .29%) 

SIN 2 91.27 91 .28 90.21 

(mean 90.92 f .59%) 

S/N 3 87.73 88.28 87.90 

(mean 87.97 *. 31 X) 

S/N 4 87.90 88.10 87.72 

(mean 87.91 * .22%) 

Notes: SIN 1 and 2 are newer units and SIN 3 and 4 are older 

units. 

The calibration ratio for use in correcting measured dati 

is defined as the nominal scale factor of 100 V/(A/m) 

divided by the cal i brated scale factor. 

Table 3-5. Calibrated scale factor-search-coil and 

post detection amplifier. 
Channel Gain Ratios 

X Y z 

SIN 3 4.968 4.970 4.973 

SIN 4 4.974 4.962 4.977 

Tab1 e 3-6. Post detection amp1 ifier. 
Scal e Factor (V/ (Alm) ) 

X Axis Y Axis Z Axis 

Unit (EN) (NS) (Vert. ) 

SIN 1 18.32 18.34 18.28 

(mean 18.31 %.16%) 

SIN 2 18.35 18.34 18.17 

(mean 18.29 +.49%) 

SIN 3 17.66 17.76 17.68 

(mean 17.70 a.28%) 

SIN 4 17.67 17.75 17.63 

(mean 17.68 k.342) 

Note: SIN 1 and 2 are newer units, and SIN 3 and 4 are older 

units . 

Table 3-7. Scale factor referred to search coil output. 
4.0 TEST OF ATMOSPHERIC NOISE CANCELLATION BY USING A REMOTE SENSOR 

The abi 1 i ty to locate miners trapped in deep mines (1,000 m) from the 

surface is directly dependent on the ability to largely eliminate the 

effects of natural and man-made noise. There is some limited experimental 

evidence that natural noise can be cancelled more than 90% by using a 

remote sensor. 5 

Therefore, spatial correlation and cancellation of atmospheric noise 

using long baseline differences from a remote sensor was considered as a 

possible means for achieving one of the necessary noise reduction methods. 

(Impulse noise processing is also necessary, but this will only reduce high 

level peaks and compress the range of variation.) In this approach, the 

remote reference, or "far" sensor, is placed 10 times as far from the 

beacon transmitter (10-20 km) as the most distant "near" sensor (1-2 km) so 

it is exposed to a signal amplitude of less than 0.2% of that at any other 

sensor and can be considered a sample of pure noise. 

The tests on this program were conducted to determine if a cancellation 

of 20 db, or down to the search coi 1 noise 1 imit (whichever is greater), 

could be achieved using amplitude correlation only. 

4.1 LOCATION AND SETUP 

The remote sensor cancellation tests were performed at the USGS Stone 

Canyon Seismological Observatory, which is 15 miles (24 km) south of 

Hol 1 i ster , Cal ifornia, with their cooperation and permission. The speci fi c 

sites were chosen based on low cultural noise, available nearby phone 

drops, access and security . The "local" sensor site was located in a field on a hi 11 approximately 

112 mile west of the Stone Canyon Observatory itself. An inactive 

powerline ended about 100 yards from the site and 60 Hz interference was 

normally not observable. (Leakage from a damaged cable was a problem in 

wet weather, but the power was subsequently turned off.) 

The *remoteN sensor site was situated in a field behind the California 

Division of Forestry fire station at Bear Valley. The distance to the fire 

station and the nearest powerlines was on the order of several hundred 

yards. 

The straight line distance between the two sites was approximately five 

miles (8 km) and roughly parallel to the nearby (114 to 112 mile or so) San 

Andreas fault, in hilly terrain. The valley is agricultural and the hills 

are ranch land. The geology is highly faulted and irregular, so these 

sites should represent a "worst case", i.e., minimum correlation. 

Each 3-axis sensor was mounted close to the ground with the lower half of 

the vertical axis in a shallow pit. Adjustable mounting feet were driven 

into the ground to provide stability and leveling. The horizontal 
axes were oriented N-S, E-W with a hand compass. A pyramid wind screen was 

placed over the sensors and weighted down. 

The sensors were positioned in open areas away from trees, fences, etc., 

to minimize the possibility of wind-induced seismic noise, but it could not 

be verified if this was successful. However, numerous ground squirrels at 

Bear Valley, the unexpected herding of cattle at Stone Canyon after 

installation, and the severe winter storms were definite sources of 

uncorrelated noise at times. This can be prevented in future operations by 

hardening (concrete pads, secure shelter) and area fencing. 

Analog data was transmitted from the field sites over standard voice 

yrade telephone lines by using the data grade VCO's (Voltage Controlled 

Oscillators) and discriminators as shown in Figures 4-1 and 4-2. 

Recordings were made at selected times (e.y ., day and ni yht) with a Teac 

K-61 Cassette Data Recorder. 

The post detection amplifier, used for these tests, amplifies the search 

coil output and notches the powerline harmonic interference at 60, 120 and 

180 Hz. It was placed close to the coil assembly to minimize possible 

noise pickup on the coil output cables. 

Three Develco 6242 VCU units were mounted inside a weather resistant box, 

which also contained two 12 V "Gel-Cell" (lead acid) batteries (4.5 A-H 

each) and a telephone line coupler. One battery powered the search coils 

and post detection amplifier and the other battery powered the VCO's. The 

telephone coup1 ing circuit provided off-hook simulation and a timer that 

maintained data transmission for 25 minutes after detection of the ring 

tone. It also powered two relays that connected the batteries only during 

data transmi ssi on. 

The upper limit of the system passband frequency response is limited by 

the VCO-Uiscriminator combined transfer function which is down 3 db at 

approximately 20 Hz. The low frequency response is limited by the ac 

coupliny network in front of the VCO input and is approximately 4 Hz. The 

overall attenuation at 60, 120 and 180 Hz was 90, 80 and 90 db, 

respectively. The combined ctannel gain of the search coil, post detection 

amplifier and VCO was 12 x 10 V/(A/m) and the recorder gain was 

inputloutput = 110.29. 

Since the recorder only had four channels, the procedure was to record 

one "local" (Stone Canyon) channel and all three "remote" (Bear Valley) 

channels at a given time. The procedure was repeated in turn for XL, 

YL, and ZL for a given data set. 

4.2 OATA ANALYSIS 

Three received atmospheri c noise si ynal s from one "remote" orthogonal set 

of sensors and one additional "local" noise signal were recorded 

simultaneously and so retrieved for the following analysis. The three axes 
VCO 8ottingm 

- STATXOU - AXIS VCO Croquurcy VW Attonrution 

Bur V~lloy XR 

Telephone Coupling 680LII 1- 

C Thr Modulo Y1 136- lod) 

aa 204wt 1- 

AC COUPLING WITH A POLE 

AT 5)N//m (U) 

FIGURE 4-1. Noise Data Transmission Setup. 

ot the ful l set were designated Xu, Yu, and LR. The XK search coi 1 

was oriented E-W and YK, N-S. XR, YK were both horizontal and ZE 

vertical . The local si ynal was selected out of a second orthoyona l set 

designated XL, YL, and LL. The axes XL, YL, and ZL were 

roughly aligned with a maynetic compass to have the same orientation as 

XK, YK, and Zu, respectively. It was thus expected that 

correspondiny siynals from the two sites would be highly correlated and 

yood cancellation could be acnieved with yain ad~ustment alone, withuut 

hdvi ng to add orthobonal coniponents . A Uata Precision Model 6UUU Wavetorm Analyzer was used to take FFT's ot 

the data and display the results in terms of power spectral density. This 

was done by Taking 512 samples, with a sarnpliny period of 5 ms, perforniiny 

the FFT and squariny it. This was repeated and the data stacked (summed) 

on the Order of 2UU to 4UU times (see Appendix I). 

Frurn measurement of the full bandwidth KMS of the recorded noise, it was 

verified that there was no significant change in tne noise power during a 

period of one recording (40 minutes). Thus, in a cancellation measurement 

it is possible to minimize the residual noise with a single setting of yain 

conipensation, assun~iny only that the the spectral distribution is stable. 

This yain wi 1 l be different for different frequencies because of 

differential yain and phase shifts between channels. Figure 4-3 shows the 

residual noise level YL-KYR (not in the same scale) as a tunction of K 

for a particular data set. 

FIGURE 4-3. Relative gain (K). 
As is clearly seen it is possible to choose a gain that will give 

sati sf actory resul ts for a span of frequencies and this gai n may a1 so be 

found by: K = YI (1 

YR(RMS) 

It was confirmed that direct subtraction, with appropriate gain 

adjustment, of para1 1 el axes di d indeed produce the best resul t, si nce no 

apparent improvement coul d be achieved by cross coup1 ing orthogonal 

ampl i tude components i nto the sumni ng network (e. g., +KxXR and 

+KzZR into YR) . This indicates the correlated noise fiel d direction 

was essentially the same at both locations. 

Some representative results for ambient and cancelled atmospheric noise 

levels are shown in Table 4-1, where the values are in dBHo relative to 1 

A* /m2 HZ, and Figures 4-4 through 4-6. Note the Schumann resonance 

maximums at 8, 14 and 20 Hz and minimums at 5, 11 and 17 Hz, are clearly 

visi bl e on the horizontal components. The resul ts obtained with recorded 

data are consistent with both earlier preliminary measurements and the 

FFT's from real-time signals. 

The best cancellation results were achieved by subtraction of the 

Y-channel ampl itudes from the two sites. Table 4-1 illustrates that the 

results could be duplicated at different times of day and on different 

days. At 5 and 11 Hz the cancelled amplitudes are approaching the search 

coil noise 1 imi t. These 1 evel s are approximately 30 dB be1 ow the Develco 

l/f noise model and approximately 20 dB below the typical levels for 

temperate zones (e. g . , Maxwell and Stone's Ma1 ta data). l1 The apparently 

uncorrel ated residual atmospheric noise at the Schumann resonance peaks (8, 

14 and 20 Hz) is probably simply due to the higher amplitude at these 

frequencies, which is of no consequence since the operating frequency will 

be at a minimum. 

The cancel 1 ed resul ts for the X (horizontal 1, in particular, and Z 

(vertical) axes were not as good but are within the goal for the expected 

noise level due to cancellation alone. In the case of the X axis, it is 

suspected that the higher noise level may have been a system problem since 

the noise 1 evel of the X axis used at the remote site became very high after the recording work was completed, and had to be repaired. Also, 

better results had been obtained for the X axis during preliminary tests 

prior to the recording phase. 

The nominal ambient 1 evel s of the vertical (Z axis) fiel ds are on the 

order of 10 to 20 dB 1 ower than the horizontal fiel ds, as is expected in 

regi ons with horizontal 1 y strati f i ed earth conducti vi ty . For the data 

illustrated in Figure 4-5A, there is some evidence of the resonance at 

8 Hz. However, there is clearly some additional interference at the remote 

site. Cancellation did not result in any substantial reduction in this 

case, probably because the 1 evel is a1 ready approaching the search coil 

noise, which is 1 ow enough. 
*Tne fiyures correspond to minimas ana maximas. The actual frequencies at 

which they occur deviate from the above frequencies up to about k0.2 Hz. 

Table 4-1. Sunmar% of cancellation results (in dBHo relative to 

1 ~'/m Hz). 

u 

YL-0.88 YR 

XI? 

XR-0.88 XL 

y R 

YL-0.87 YR 

z R 

L 

Remarks 

from 6:20 a.m. 

recordiny on 

1/11/83 

from 5:30 a.m. 

recordiny on 

1/11/83 

from 7:30 p.m. 

recording on 

1/12/83 

from 10:20a.m. 

recording on 

1/7/83 

Bucked 

5 

-140.1 

-147.1 

-140 

-143 

-141 

-147.6 

-144.8 

-146.2 

17 

-134.7 

-153.2 

-143.2 

-147.4 

-136 

-153.2 

-149.2 

-148.9 

No substantial reduction even with gain 

adjustment. 

20 

-132.6 

-151.4 

-140.9 

-147.4 

-133.4 

-149.9 

-149.2 

-149.2 

14 

-129.7 

-150.7 

-137 

-144.4 

-132.6 

-150.8 

-148.4 

-143.6 

8 

-130.3 

-146.6 

-131.7 

-142.2 

-130 

-144.6 

-142.4 

-139.7 

11 

-136.9 

-152.1 

-141.3 

-144.7 

-136.3 

-152.7 

-147.2 

-147.2 
Figure 4-4. Typical Spectral Display for a Hariz3ntal Coil 

A. Individual Remote Site 

YR, sum of 250 squared FFT's, 512 samples each, 5 ms 

sampling interval from J:30pm recording on 1/12/83. m 

B. Noise Residue after Cancelling 

YL - 0.87Y , sum of 400 squared FFTr s, 512 samples each, 

5 ms saapling interval from 7:30pm recording on 1/12/83. 
Figure 4-5. Typical Spectral Di sp1 ay for Vertical Coi 1 s 

A. Local Site 

t , sum of 405 squared FFT's, 512 sae~les each, 5 rns 

'sampling interval from 1D:ZOam rec-ding on 1/7/83. 

£3. Remote Site (note differences between the two sites,) 

ZR, details same as above. 
FIGURE 4-6. Comparison of Resul ts with Theoretical Hoi se Limit

* The theoretical noise reduction limit for cancellation is 

approximately -153 dBHo, or an intrinsic noise level of 

-156 dBHo per coil, at I0 Hz. 
In summary, this limited test and evaluation has shown that the desired 

noise levels can be achieved with cancellation. Even though the actual 

ambient noise levels were 10 to 20 dB lower than the "Develco Model", the 

cancelled result is approaching the search coil noise limit particularly 

at the 11 Hz minimum ( for the specific gain constant, Ky used in this 

case). This suggests that the uncorrelated noise due to geological, seismic 

and electronic factors is sufficiently low that similar cancellation levels 

can be achieved even under conditions of higher ambient atmospheric noise 

1 eve1 s. 

4.3 CONCLUSION 

The experiment described above, a1 though 1 imi ted in scope, clearly 

demonstrates the expected properties of remote cancellation, and has 

achieved adequate noise levels for location of a trapped miner at a depth 

of 1 km, through overburden with an average conductivity of 0.01 S/m. For 

instance, with a transmitter vertical moment of 700 Am2RMS at 5.3 Hz, the 

field at the surface within a horizontal radius of 500 meters of the 

transmitter's vertical projection will be at least 7 x 10-~A/m, or -143 dBH. 

From Table 4-1, the worst case measured noise density at this frequency 

after cancellation is -143 dBHo on the X-axis. The signal-to-noise ratio 

is therefore 0 dB in 1 Hz bandw'dth. For N dB improvement by time averaging, 

the required time is T = 1/2 10 1 N/lO). Thus, a 40 dB SNR can be achieved in 

5,000 seconds, or about 1.4 hours. If the X-axis amplifier was excessively 

noisy as suspected, the required averaging time could be reduced by as much 

as one-half. 

It should also be noted that this experiment did not take advantage of 

phase correction, axis alignment correction, or impulse noise processing 

after cancel lati on. Each of these refinements , as shown by Raabg and 

Develco3 can potentially provide further noise reduction. In particular, 

impulse processing has been shown by ~vans" and others to have increased 

effectiveness when the impulsiveness of the noise increases, such as might 

result from nearby thunderstorm activity. 

The season and locale of the remote cancellation tests resulted in 

relatively low absolute noise levels, masking the available improvement 

that might be afforded by the above techniques. Therefore, it is 

recommended that operational systems incorporate fully adaptive amplitude, 

phase, and alignment cancellation, and that impulse noise processing be 

incorporated in the signal chain following cancellation. 
5.0 IN-MINE LOCATION TEST 

5.1 SITE DESCRIPTION 

The field test was conducted at the Kerr-McGee potash faci lity near the 

town of Hobbs in the flat Permian Basin area of southwestern New Mexico. 

The mine has a single level extending laterally over some 80 square miles, 

sloping 1-2 degrees down to the northeast. The test site was in the 

southwest area of the mine, where the depth below surface is about 1,250 

feet. The surface conditions in this area include reddish-brown soil with 

a hardpan layer 1-2 feet down; the only vegetation supported are low, 

sometimes dense, brush, grass, and cactus. 

The site had been designated by the mine engineer as a relatively flat 

area on the surface at some distance (1,000-2,000 feet) from the nearest 

power line and with convenient access to several areas of the tunnel 

network below. Four stations (D-1 through D-4) were surveyed about 500 

feet apart in a pattern that would allow the surface sensors to be 

installed in either a colinear or triangular array (Figure 5-1). The 

ground slopes from the area of the stations down into a canyon to the 

northwest. Two preliminary loop positions were selected down in the mine, 

one large (LP-1) and one small (LP-2). The surface station positions were 

measured by the mine engineer in the mine coordinate system, which 

arbitrarily designates the production hoist tower as 50,000 feet N and 

50,000 feet E. The mine coordinates were tied to the surface through 

section markers. The coordinate system actually used in the location tests 

had its origin (0 N, 0 E) translated to mine coordinates 46,000 N, 44,000 E 

to reduce the magnitude of the sensor and transmitter coordinates, since a 

preliminary run using the actual mine coordinates was apparently hampered 

by the large linear dimensions (this deficiency in the software has since 

been corrected). Station D-3 was arbitrarily set at zero elevation (Z=O). 

5.2 SENSOR SYSTEM INSTALLATION 

The basic scheme for installing the sensors was to place and orient the 

sensors approximately as desired and then measure the exact placement and 

orientation of the sensors in a known coordinate system. Because of time 

constraints, the only array shape used in the field test was colinear, with 

sensors A, B, and C i n s t a l l e d at stations D-1, D-4, and D-3, respectively. 

The basis for positioning the sensors were large survey stakes that were 

placed by the mine engineer at the stations; the exact position of the 

stakes was known in the mine coordinate system. The sensors were installed 

roughly along the base1 ine between the stations, but brush surroundi ng the 

actual surveyed stake positions required the positions of the sensors to be 

10-15 feet away along this base1 ine. The Y-axes of the sensors were 

aligned approximately along the baseline, with the positive Y-axes to the 

northeast. Since the stake positions were known within the mine coordinate 

system, the sensor positions had only to be determined locally with 

reference to the stakes. Some of the local measurements were made using a 

battery-operated auto-leveling construction 
'1 

FIGURE 5-1. Plan View of In-Mine Test Location. 
laser with a head that rotates 360 degrees about a horizontal axis; this 

allows the beam to be aimed anywhere in a vertical plane perpendicular to 

the rotation axis. 

A shallow (1-2 foot) hole was dug for the lower Z-axis of each search 

coil assembly (Figure 5-2). The four horizontal axes (+X, -X, +Y, -Y) are 

desiyned to be held in place by fiberglass clamps mounted on brass stakes. 

First, two stakes were driven into the ground to support one arm of the 

search coil on the lower half of the brackets; the brackets were adjusted 

until the arm was resting level. The two remaining stakes were then driven 

in alongside the remaining arm and the lower half of the brackets adjusted 

to support the arm in a level position without lifting the other arm out of 

its brackets. Once the search coil was resting level and firmly on all 

brackets, the upper part of each bracket was clamped down to hold the arms 

securely in position. 

At each sensor position, a local baseline was set up by using a transit 

to position a small stake on each side of the large stake at a distance of 

about 20 feet along the baseline. The survey laser was then placed exactly 

along this local baseline by lining up its beam with the two stakes; it 

could then be used to establish the baseline at any point i n i t s 360-degree 

arc. By measuring from the sensor over to this baseline and then along the 

baseline to the larye stake, the displacement of the sensor from the large 

stake could be resolved into its components in the mine coordinate system, 

thus determining the horizontal position of the sensor (Table 5-1). The 

vertical position of each sensor was simply estimated, since no accurate 

data were available. Sensor C at station D-3 was arbitrarily set at zero 

elevation (Z=O). A very yradual slope to the west suggested that sensor I3 

(Station 0-4) was at perhaps -3 feet and Sensor A (Station D-1) was at -6 

feet. 

The azimuthal bearing of the positive X-axis of each sensor was measured 

in degrees clockwise from north (Table 5-1). This was done by positioning 

the laser at the same heiyht as the mirror mounted on the sensor, aligniny 

the laser beam parallel to the baseline, deflecting the beam off the mirror 

and back to the laser position, measuring the distance subtended by the 

beam at the laser position, dividing that distance by the distance from the 

laser to the mirror, taking the arctangent of the result to get the 

subtended angle, dividing the subtended angle in half to get the deflection 

angle, adding (or subtracting) the deflection angle to the azimuthal 

direction of the baseline to get the azimuthal direction of the positive 

Y-axis of the sensor, and then adding 90 degrees to get the direction of 

the positive X-axis. In two cases the mirror was close enough to the 

baseline (1-2 inches) and the laser was at the right height to leave the 

laser in the position used earlier to locate the sensor position. In the 

third case, the mirror was about 20 inches off of the baseline, so another 

line was set up on line with the mirror and parallel to the baseline. The 

deflection angle was measured as before to obtain the azimuthal orientation 

of the X-axis. 
FIGURE 5-2. Three-axi s search coi 1 surface sensor measures signals from 

transmi tter-loop in mine. 

FIGURE 5-3. Sensor Data Unit processes z i gnal s and displays amp7 i tude 

and phase information. 
As an experimental procedure, the sensor orientations were a1 so measured 

using a hand-held compass. The pertinent bearing is the direction of the 

positive X-axis of the sensor measured in degrees clockwise from north. 

Two sightinys were taken on each sensor, one siyhtiny down alony the 

positive X-axis and the other back along the negative X-axis. Each pair of 

measurements agreed to within 1.5 degrees; the averayes of the pairs were 

used as the sensor orientations in a trial location calculation (see data 

set 11 under Location Test Data). 

Station Sensor X-Pos (ft) Y-Pos (ft) Z-Pos (ft) X-Az (deg) 

Table 5-1. Sensor positions and azimuthal orientations. 

Positions are measured in a translated version of the 

mine coordinate system. Azimuths are measured 

clockwise from north. 

To complete the installation of each sensor, the search coil leads were 

then connected to the post detection amplifier. After unreeling the 1,U00' 

cable and connecting it to the post detection amplifier, the packiny crate ' 

was set upsidedown over the search coil as a windscreen, with only a small 

tunnel opening at its base for the cable to exit and for access to the 

switch on the amplifier. Three burlap bays were filled with about 80 

pounds each of dirt and set on top of the crate with as low a profile as 

possible. Each 1,000' cable was then connected to a preamplifier, which 

was then connected over a short cable to its matchiny Sensor Data Unit 

(SDU, Figure 5-3). 

The SDU's were placed in an equipment van (Figure 5-4) along with the 

Location Analysis Unit (computer, disk system, and printer) and a 14-track 

Honeywell recorder. The van was parked alony a road that runs just north 

of the fence line (Figure 5-l), about 300 feet south of Station D-4. Ac 

power was supplied by a trailer-mounted generator parked about 30 feet from 

the van. 

Two kinds of tape recordings were made for future analysis; signal plus 

noise during the location tests and noise only at various times. The 

14-track Honeywell 1010 FM Recorder used was set up for +1 V maximum 

deviation, 54 kHz center frequency, and [RIG WB Group I,15 ips operation. 

The tape SNR was approximately 44 to 49 dB relative to the maximum record 

level . The typical signal plus noise level was on the order of +50% full 

scale, with occasional higher peaks (recorder cl ippiny would occur at about 

20-40% over full scale). Ideally, all three SDU's should be run in the 

fixed-gain mode but this was found to be unnecessary since the front-end 

gain ratio stayed at a constant level of 128; in addition, the yain should 
rlbUKt 5-5. Computer calculates transmitter location based on informatiori 

from the 3 Sensor Data Ilnitc 
not be fixed when acquiring location data. Recordings were made of a1 1 

nine sensor channels at the analog outputs of the three SDU's, along with a 

stable 25 kHz reference frequency for playback speed control. 

5.3 TRANSMITTER INSTALLATION 

Three transmitter-loop positions were used during the location tests 

(Figure 5-a), with a project name assigned to each position as follows: a 

920 ' ci rcumference loop at LP-1 was Project KM02, a 470' loop at LP-2 was 

Project KM03, and a 380' loop at the spontaneously selected position LP-3 

was Project KM04 (Project KMOl was assigned to the system checkout below). 

Each loop was laid out along the perimeter of one or more pillars and 

connected to the modified transmitter; the transmitter was powered by two 

cap-lamp batteries connected in parallel. Loop deployment and transmitter 

operation were done just prior to each test on a prearranged schedule, 

since there was no communication with the surface test site. Operating 

time was limited by the necessary preparations before each test and the 

hoist operating schedule in the afternoon. The duration of transmission 

ranged from 25 minutes to two hours (Table 5-2), with an average battery 

discharge rate of about 50 mV/hour. Loop current was measured with a small 

portable osci 11 oscope and a 1 ow-val ue series resistor. The transmitter 

operating frequency was 10-2/3 Hz. The gauge and length of the wire used 

varied between the three loop positions to keep the resistance close to the 

nomi nal 2-ohm standard (Tab1 e 5-3). 

The estimated moments ranging from 4,868 to 759 ~rn~ were calculated from 

the measured currents and the enclosed loop areas as scaled from the mine 

map. The differences between these estimated moments and the mean moments 

from the location calculations are probably due mainly to errors in scaling 

the loop dimensions from the map. Since the measuring equipment has been 

accurately calibrated, the moments from the location calculations are 

probably correct. Although2a standard 300' loop was not installed, the 

calculated moment of 678 Am for a standard loop (Section 2.4) is on the 

same order as that actually obtained from the 380' loop used at LP-3 

because of the higher resistance and thus lower current. 

5.4 SYSTEM FUNCTIONAL CHECKOUT 

Sample atmospheric noi se measurements were made to veri fy the stabi 1 i ty 

of the sensor installations and that the noise levels would be low enough 

for proper location system operation. A narrow bandpass filter with a 

center frequency of 8 Hz, a noise bandwith of 2 Hz, and a gain ratio of 45 

was connected to the broadband analog output of each of the three SDU's in 

turn. The front-end gain ratio of each SDU was 128. Voltage measurements 

were made with an HP403 low-frequency RMS voltmeter. The conversion to 

equivalent field assumed a combined sensor and post detection amplifier 

scale factor of 100 V/A/m. 

Position 1 Position 2 Position 3 

4-Pi 11 ar 2-Pi 1 1 ar 1-Pi 11 ar 

Units ( InitIFinal ) ( InitIFinal ) ( InitIFinal ) 

Loop resi stance1 ohms 2.8/--- 3.51--- 2.71--- 

Battery voltage 

No load V 4.19414.105 4.1001----- 4.21014.045 

Load V 4.05214.106 4.04114.014 4.09013.986 

Loop current (~k)~ A 1.10 11.10 0.90 10.90 1.11 11.11 

Duration mi n --I60 --I25 ---I120 

1 

2 

Does not include 0.1-ohm resistor used for current measurements. 

Measured using the 0.1-ohm series resistor, which is always in the 

ci rcui t during transmission. 

Table 5-2. Transmitter parameter measurement sumnary. 

Position 1 Position 2 Position 3 

Uni ts 4-Pi 11 ar 2-Pi 11 ar 1-Pi 11 ar 

Loop Dimensions 

Loop Ci rcumference 

Enclosed Area 

Wire Gauge 

Wire Length 

Wire Resistance 

Peak Current 

Peak Moment 

RMS Moment 

Mean Moment 

feet 

feel 

ft 

m 

AW G 

feet 

ohms 

A 

Am 

Am 

Am 

lBased on scaled dimensions from mine map. 

2Trapezoidal pi 11 ar, see Figure 5-6. 

3Measured val ues . 4KMS moment referred to the fundamental for a square-wave is 

25 

mO(KMS) = -NAIpk 

pi 

5Based on results of location calculations (RMS). 

Table 5-3. Transmitter-loop parameters and moments. 
These atmospheric noise measurements were made in the late morning on 

October 10, before the sets of signal measurements for location projects 

KM02 and KM03. The results were essentially indentical on each 

corresponding axis at each sensor station (Table 5-4) and are consistent 

with expected atmospheric noise levels based on previous measurements. In 

addition, the vertical field is approximately 20 dB lower than the 

horizontal field, as is expected in regions with horizontally stratified 

earth conductivity. The weather conditions at the time of the measurements 

were mildly breezy and partially overcast, although it was cloudier to the 

southwest and there could have been distant thunderstorms. It was 

concluded that the windscreens placed over the sensors were adequate. 

Axi s Average* Horizontal Total Expected 

X (horiz) -129 to -126 -121 to -119 -126 

Y (horiz) -121 to -120 

Z (vert) -144 to -138 -146 

* This is the mean of the typical levels, as determined by observing the 

meter over some period of time. Occasional impulses can cause 

considerable variation. In this case, the Y-axis was the most variable 

with occasional fluctuations of +6 dB. 

Table 5-4. Typical measured atmospheric noise levels at 8 Hz. 

All values are in dBHo relative to 1A2/m2/~z. 

Since the search coil sensor stations were within 2,000 feet of a surface 

high-voltage powerline (within 1,000 feet at D-3, the closest station) and 

approximately 1,200 feet from underground powerlines, 60 Hz interference 

was of potential concern. However, measurements made near D-3 showed the 

pre-60-Hz notch filter levels on all three sensor axes were approximately 

two orders of magnitude below the search coil post detection amplifier 

saturation level (5 V referred to the output). Typical values were less 

than 300 micro A/m peak or -70 dBH. The horizontal axis perpendicular to 

the surface powerline had the highest value. The vertical axis value was 

about 2 dB less and the orthogonal horizontal axis value about 6 dB less. 

After the 920-foot loop was installed around the four pillars at position 

LP-1, a preliminary test was conducted to check system functions and verify 

that signal and noise levels were suitable for location measurements. The 

data obtained for this case were designated as Project KMO1, even though 

the data were not used in any location calculations (ensuing location tests 

were designated as Projects Kf402 through KM04). 
One of the SDU's had a minor display ma1 function that was not repaired 

until the following day, so that only two units were available for taking 

data on October 9. The system checkout was continued meanwhile with one of 

the two good SDU's being used to monitor two of the three sensors by 

switching the sensor cables back and forth. This switching of the cables 

(in effect, multiplexing) defeats the long-term integration of the data, 

which might adversely affect the results of a location calculation, but the 

method was sufficient to verify expected signal and noise levels during the 

functional checkout. 

The measured signal and noise levels compared we1 1 with those expected 

for the configuration, with one exception: one of the channels from 

sensor C was found to have a signal level far below even the expected 

atmospheric noise levels. This problem was traced to holes in the cable 

that had evidently been chewed by some small animal (s), e .g., pack rats. 

The damaged section was removed and the cable fittings reconnected. Less 

extensive damage to the other two cables required only minor repair. Mine 

personnel suygested that chewing animals are particularly attracted by 

salty sweat residue deposited during handling of the cable, although the 

insulation itself is, in many instances, the objective. 

5.5 LOCATION TEST DATA 

The coordinate system used in the field test was right-handed and 

orthoyonal, with the Z-Axis positive upward and the positive X-Axis 

pointing at 90 degrees clockwise from north. The origin of this coordinate 

system (Figure 5-6 is located at mine coordinates 46,000N and 44,000E. 

Sensor C was arbitrarily set at zero elevation (Z = 0). 

Fifteen complete sets of sensor data were recorded, at 10- to 15-minute 

intervals, from the three different loop positions. Each loop position was 

designated as a separate project; these were named KM02, KM03, and KM04 

(Project KMOl desi gnates the checkout of the system functions). These 

three projects have six, two, and seven sets of sensor data, respectively. 

One set of sensor data (No. 2) from Project KM02 was modified in various 

ways to create five experimental additional sets of sensor data (Nos. 

7-11). All of the sheets containing the project information and sensor 

data are given in the appendix. 

Project KM02 designates data collected on October 10, 1984, from the 920' 

loop at LP-1 (Figure 5-6. . The first six sets of sensor data (Nos. 1-6) 

were collected from 12:33 to 13:30. The Sensor Data Units were reset 

before the first set of data was taken and reset again before the third 

set. The data sheets for these six sets follow the project information 

sheet for Project KM02 in the appendix. 

The next three sets of sensor data (Nos. 7-9) are modified versions of 

the set of sensor data collected at 12:45 (No. 2). These three sets 

represent, in turn, the omission of data from sensors A, B, and C, so that 

data from only two sensors are used in each case. This was done to 
evaluate the performance of a two-sensor sytem. The pro~ect information 

had to be changed to reflect the omission of the one sensor in each case, 

so that three new projects were aesiynated KMBC, KMAC, and KMAt3, 

respectively. The pro~ect information sheets and corresponding sensor data 

sheets appear in the appendix following the sheets for data sets 1-6. 

Sensor data sets 10 and 11 represent modifications in the azimuthal 

directions of the sensors, using the data collected at 12:45 (No. 2). Set 

10 discarded the local rotations of the sensors from the sensor baseline, 

or, in other words, it assumed that all sensors were pointing in exactly 

tne same direction of 150.1 degrees clockwise from north. This introduced 

angular rotation errors of +4.9, -0.9, and +2.6 degrees at sensors A, B, 

and C to evaluate the sensitivity of the system to such errors. This 

required a revision in the project information, so that a project 

information sheet and sensor data sheet for a project named KMNR have been 

included in the appendix. Set 11 introduced the same kinds of rotational 

errors, but in this case the azimuthal values represent readinys from a 

hand-held compass used to siyht along the sensor. The angular errors in 

this case were +1.2, +0.6, and +1.5 degrees; these data appear in the 

appendix under project KMCR. 

Project KM03 designates data collected on October 10, 1984, from the 470' 

loop at LP-2 (Fiyure 5-6. The two sets of sensor data (Nos. 12 and 13) 

were collected at 13:45 and 13:55, startiny two minutes after a reset of 

the Sensor Data Units. The data sheets for these two sets follow the 

project information sheet for project KM03 in the appendix. 

Project KM04 designates data col lected on October 11, 1984, from the 380' 

loop at LP-3 (Figure 5-6. The seven sets of sensor data (Nos. 14-20) 

were collected from 10:50 to 12:25; the tirst set (No. 14) was taken within 

two minutes of resettin9 the Sensor Data Units. The data sheets for these 

seven sets follow the project information sheet for project KM04 in the 

appendi x . 5.6 LUCATION RESULTS 

Each set of sensor data (along with its corresponding project 

information) was entered into the computer running the LocatorIDLMG 

software (Fiyure 5-5). The result from each set of data is an X, Y, 

Z-location of the source transmitter-loop, the tilt of the loop in degrees 

from horizontal, and the moment of the loop in ampmeters-squared (Am2) 

(Table 5-5). The horizontal location of each result is generally very 

close to the center of its corresponding loop position (Figure 5-6). The 

notable exceptions are data sets 7-11 (the modified sets) and data set 14. 

The location results from the unmodified sets of data (Nos. 1-6) are 

tightly grouped near the geometric center of the loop at LP-1 

(Figure 5-7), with a mean depth of -1,241 feet. The mean location is 

offset from the center of the loop by about 10 feet to the south and seven 

feet to the west. The approximate depth in this area was given by the mine 
FIGURE 5-7. Location Results from Data Sets 1-6. Dots represent 

individual results; the mean is shown as a triangle. 
enyineer as -1,250 feet. The standard deviation of the location results is 

about five feet in the horizontal direction and seven feet in the vertical 

direction. The mean tilt value is three degrees from horizontal; the mean 

moment i s about 4,900 AmZ'. 

The location results from the sets of data using two sensors (sets 7-9) 

are scattered somewhat farther from the center of the loop (Fiyure 5-6), 

but still fall within its perimeter, with depths ranyiny from -1224 to 

-1240 feet. The farthest off ot these is set 7, which uses only the data 

from Sensors B and C. It should be noted that, in this case, the 

transmitter-loop is located close to the vertical plane of ambiguity which 

bisects the line between the two sensors being used. In addition to 

increasing the error in the resulting location, beiny close to this plane 

produces an unusually high tilt value ot 11 deyrees from horizontal. Usiny 

the data from sensors A and C (set 8) or Sensors A and B (set 9) produces 

location results that are closer to the center of the loop and have more 

reasonable ti 1 t val ues (5-6 degrees). 

The location results from set 10 are the worst of any, lying 25U feet to 

the northwest of the loop center (Figure 5-6. The tilt indicated is 29 

degrees from horizontal. Although the rotational errors introduced in this 

case by assuming that the sensors are aligned with the baseline (see 

Location Test Data) cause a siynificant deviation in the location result, 

the result miyht well be satisfactory as a first quick estimate. The 

location results from set 11 are much better than those from set 10, in 

accordance with the lower rotational errors introduced by using the compass 

readings for the azimuthal directions of the sensors (see Location Test 

Uata). The horizontal location is about 40 feet from the cluster of 

results from data sets 1-6. The depth is -1227 teet, with a tilt of six 

degrees and a moment of about 490U Am2. 

The location results from data sets 12 and 13 are we1 1 within the 

perimeter of the loop at LP-2 (Fiyure 5-8), although they are more 

scattered than the results from sets 1-6. The sensor data used here are 

somewhat noisier than for the previous position because of the smaller 1001 

size; the readinys from Sensor C are particularly noisy because of the 

fall-off in signal strength. The mean of the two location results is 12 

feet to the south and one foot to the east from the center of the loop. 

The mean depth is -1196 feet; the mine engineer indicated a depth of about 

-1225 feet in this area. The standard deviation of the location results is 

about 30 feet in the horizontal direction and 25 feet in the vertical 

direction. The mean ti1 t value is five deyrees from horizontal ; the mean 

moment is about 850 Am2. 

The only exception to the small cluster of location results near the 

center of the loop at LP-3 is the result from data set 14 (Figure 5-6). 

The horizontal location is over 100 feet south from the center of the loop, 

the indicated depth is nearly 65 feet shallower than the nominal depth, and 

the indicated tilt is about 15 deyrees steeper than the nearly-level mine 

floor. This data set was the first recorded after resetting the Sensor 

Data Units; it was taken after only two minutes of long-term integration. 
FIGURE 5-8. Locatyon Results from Data Sets 12 and 13. 

FIGURE 5-9. Location Results from @ta Sets 15-20. Dots represent 

individual results; the mean is shown as a triangle. The asterisk 

indicates the geometric center of the loop. 
In the case of this smaller and noisier transmitter, a lonyer integration 

time was apparently necessary to achieve good results. The location 

results from data sets 15-20 have a mean horizontal location about 11 feet 

to the south and two feet to the east of the loop center (Figure 5-g), with 

a mean depth of -1223 feet. The standard deviation of the location results 

from sets 15-20 is about six feet in both the horizontal and vertical 

directions. The mean tilt va'lue is two degrees from horizontal; the mean 

moment is about 700 ampmeters-squarea. 

Loop position 1 ---------- Project: KM02 ------------ 10/10/84 

Data set Time X-Feet Y-Feet Z-Feet Tilt Moment Comments 

4844 reset 

4916 

5047 reset 

4913 

49 13 

4906 

5005 without A 

4852 without B 

4904 without C 

4883 no rot. 

4884 compass 

mean results and standard deviations from data sets 1-6 

239.0 42.1 1241 3 4923 

- +3.8 - +3.4 - +7 - + 1 - +6 1 

estimated actual loop parameters 

245.8 52.5 -1250 1 4868 

Loop position 2 ---------- Project: KM03 ------------ 10/ 10/84 

Uata set Time X-Feet Y-Feet Z-Feet Tilt Moment Comments 

12 13:45 -586.4 -33.9 -1220 5 90 9 reset 

13 13~55 -527.8 -25.2 -1171 5 797 

mean results and standard deviations from data sets 12 and 13 

-557.1 -29.6 -1196 5 853 

- +29.3 24.3 - +25 - +0 - +56 

estimated actual loop parameters 

-556.2 -16.8 -1225 1 1016 

Table 5-5. Location results from in-mine field test. 

Comnents are explained under Location Test 

Data. 
Loop position 3 ---------- Project: KM04 ------------ 10/10/84 

~ataset Time X-Feet Y-Feet Z-Feet Tilt Moment Comments 

14 10:50 76.7 23.2 -1186 15 672 reset 

15 11:05 77.8 98.7 -1217 3 692 

16 11:25 68.4 104.4 -1223 2 700 

17 11:40 66.7 108.9 -1223 2 699 

18 11:55 63.1 115.2 -1225 2 699 

19 12:lO 62.6 113.8 -1226 1 699 

20 12:25 60.6 114.4 -1226 2 699 

mean results and standard deviations from data sets 15-20 

66.5 109.2 -1223 2 698 

- +5.7 - +6 .O - +3 - + 1 - + 3 

estimated actual loop parameters 

64.3 98.6 -1250 1 759 

Table 5-5. Location results from in-mine field test. 

Comments are explained under Location Test 

Data .--Continued 

5.7 DISCUSSION OF RESULTS 

The mean location results agree quite well with the estimated actual 

loop positions (Table 5-5). The difference between the results and 

the actual loop positions is generally less than 1% of the distance 

from the loop positions to the sensors. Also, the standard deviation 

of the results is as low as 0.5% of the mean range. This level of 

error compares well with the short-term system SNR values of the 

measured data, which were generally 35-45 dB (40 dB is equivalent to 

one percent). The exact relationship, however, between noise in the 

measurements and error in the results is not known and is probably not 

1 i near. 

There is a suggestion of a consistent bias in the mean location 

results of about 10 feet to the south from the center of each loop 

position (with varying offsets to the east or west). The mine 

engineer estimates an overall error of less than five feet in the mine 

survey used to locate the horizontal sensor positions, but survey 

errors in the vertical direction may be greater. The eyeball 

assumption, for example, that sensor B is at -3 feet depth (relative 

to sensor C at zero depth) and that sensor A is at -6 feet depth may 

well be off by several feet. If there is a systematic error in 

the suwey, it would produce a consistent offset in the results. In 

addition to errors in the location results introduced by noise and by 

survey errors, there are position and orientation errors made when 

installing the sensors. 
The location calculation results appear better than would be 

sugyested by the conditions and trends in the SNR values in 

Table 5-6. The elapsed time given is the approximate time since the 

last reset of the long-term block averayiny after the siynal had been 

acquired (measurements could not be made simultaneously, but were 

within several minutes of the event and each other). The short-term 

SNR is measured at the output of the SDU lowpass filter, which has a 

time constant of 15 seconds and a noise bandwidth of 0.01 Hz 

(second-order filter). In most cases, it is in rough agreement with 

the expected SNH based on calculations usiny the estimated transmitter 

moment and an assumed atmospheric noise level of -126 dBHo with the 

same bandwidth. This suggests that system operation is at or near the 

atmospheric noi se 1 i mi t . 

Project Elapsed Sensor A SNR Sensor t) SNK Sensor C SNR 

Name Time (m) L-term/S-term L-term/S-term L-term/S-term 

KM02 0 48/44 461 54 381 39 

10 341 39 41/50 34/30 

2 0 32/43 41/46 351 36 

30 32 / 42 41 / 51 35/47 

expected --I43 --I47 --I46 

KM03 0 32/36 25/34 20130 

10 25/40 25/34 20131 

expected --I36 --I34 --I28 

KM04 0 

15 

35 

60 

65 

80 

95 

expected 

1) Approximate, i .e., within a few minutes. 

Table 5-6. System Si ynal -to-Noise Ratio vs. time. 

All values in dB except as noted. 

The long-term SNR is measured at the output of the SOU blockaveraying process that operates continuously since the time of the 

last reset. For yaussian noize, averayiny snould increase the SNK by 

10 dB for every ten-fold increase in the averaging time. If there is 

any deterministic change in the transmitted signal amplitude, it will 

be interpreted as a variance and included in the SNK calculation. The 

decrease in transmitter moment amplitude caused by the decay of the 
cap-lamp battery voltage (Section 2.4) or transmitter current ri pple 

are examples of why the long-term SNR's might appear somewhat lower 

than the short-term and not improve significantly with time. In this 

case, the gaussian noise would be averaged and the correct relative 

mean signal amplitudes will be obtained even though the displayed SNR 

value is low. A correct geometrical location answer will result but 

the calculated transmitter moment will be in error. The reason why the 

displayed long-term SNR values appear to be about 10 dB lower than the 

short-term values, as well as inconsistent with the good location 

results, is not understood at this time. 

In reviewing the long-term SNR data in detail, it was observed that 

anomalously high noise conditions existed on the Y-channel of sensor A 

and the Z-channel of sensor C for project l02, as well as the Y- and 

Z-channels of sensor A for Project KM04. These spurious levels 

appeared to be on the order of 6-10 dB higher than the level on a 

normal horizontal channel. The heavy impact of the last case on the 

system SNR is shown clearly in Table 5-6. In addition, an 

intermittent noise problem on the vertical (2) channel of sensor C was 

observed in the field before and after project KM04. This was later 

identified as a ground lead problem in the sensor preamplifier and 

corrected. Ground connections in the other sensor units were also 

inspected and secured. Other possible causes of the spurious noise 

levels in the other cases are problems from the cable damage, other 

grounding problems, or condensation. These noise problems did not 

seem to seriously affect the location results, possibly because the 

levels were still relatively low and only two of nine channels were 

involved in each of the affected tests. 

The question of whether long-term averaging provides improvement of 

the location results is answered by observing the trend in the 

location results from data sets 14-20 (Figures 5-6, 5-9). There is a 

marked advance toward the center of the loop, starting with the first 

data following a reset (set 14) and ending with the data that were 

averaged for up to an hour and a half. 

Overall, the location results show good consistency and accuracy. 

The low scatter in the results from project KM02 shows the precision 

that can be expected from a source with a fairly large moment or high 

SNR. Results from Project KM03 show the greater scatter expected from 

noisier measurements (from a smaller loop) made over a short time. 

Project KM04 again showed low scatter, due in part to the longer 

block-averaging time. 
6.U CONCLUSIONS AND RECOMMEhDUTIONS 

The basic goal of Phase I1 of this proyram was to test the key features 

that would be needed in an electromagnetic system that uses 3-4 stationary 

3-axis sensors on the surface to-locate a magnetic loop antenna of limited 

size deployed by a miner trapped in a deep mine (1,000m). The major 

objectives were to verify: 

a) sensor senstivity 

b) noi se cancel l ati on feasi bi 1 i ty (in a separate test ) 

c) location method operation 

Practical, relatively compact 3-axis search coil sensors with an intrinsic noise level approximately 3 orders of magnitude lower than nominal 

atmospheric noise levels have been built and tested. These sensors have 

been used to demonstrate the expected properties of remote noise cancellation. Tni s 1 imited experiment achieved adequate noise level s for location 

of d trapped miner at a depth of 1 km throuyh an overburden with an 

an averaye conductivity of 0.01 S/m. The experiment did not take 

advantage of phase corrections, axis alignment corrections, or impulse 

noise processing after cancel 1 ation. Each of these refinements can 

potentially lead to further noise reduction. 

A breadboard location system was supplied to this proyram in order 

to evaluate the proposed location method in shallower mines prior to 

building an operational prototype for use in deep mines (1,000m). In 

addition to the sensors, the system consists of 3 Sensor Data Units, 

which serve as receivers, and a Location Analysis Unit, which is a 

portable computer with unique software for location calculation. The 

location method developed by Develco has proven effective over a variety 

of sensor array confiyurations and conditions in computer simulations, 

scaled lab-array tests, and the in-mine test. The in-mine test without 

noise cancellation conducted on this proyram demonstrated that an accuracy 

ot less than 1% of depth could be achieved in a 380111 deep mine with a 

col i near array. 

It is recommenaed that the Bureau of Mines conduct additional tests with 

the breadboard location system. At first, these should be under 

control 1 ed, nominal ci rcumstances at a shal low research mine to fully 

evaluate the basic procedures and functions. The emphasis should be on 

the methods and reproduci bi I ity of the surveying and sensor emplacement in 

the field. Then tests should be conducted at a variety of deep mines, 

including some greater tnan 4OUm, to gain experience with effects such 

as electrical interference and scattering in different environments. 

Additional investigations into noise cancellation should emphasize 

alyorithm development and testing with noise data obtained under a 

variety ot conditions . 
It should then be possible to fully determine the requirements for a 

complete prototype operational deep-mi ne 1 ocation system using noise 

cancel lation. This version might incorporate the following general 

features : 

1) A fourth sensor for noise cancellation which can be installed 

at a large distance (10-15 km) from the other three sensors 

to measure noise only for remote cancel 1 ation. 

2) Compact, low power signal acquisition/digi tizing equipment. 

3) RF data links to transmit signal information from the sensors 

and eliminate the need for long cables. 

4) Wideband, ful ly adaptive noise cancel lation and narrowband 

impulsive noise processing in software. 

5) A direct serial digital data link between the signal acquisition equipment and the computer used to make the location 

calcualtions. This would speed the collection of measured 

data and reduce the chance of recording errors. 

6) High-eff i ciency , constant 1 eve1 s'i ne wave transmitters for 

miners would eliminate harmonic interference and signal 

decay, and extend battery life. 
Appendix I. Sumnary of method used to determine power spectral density 

for cancellation tests. 

Proyram used for the sumnation of FFTs on the Data 6000 Wave Analyzer (Data 

Precision, Anal ogic Corp .) : 

10 MAGCAl = FFT (Buf A1,,0,0,0,3) 

20 SQ.A1 = SQ (MAGCAl) 

30 ADD.Al = ADD.Al + SQ.Al 

Calculating the power spectral density: 

R = reading on display (cursor 'ONn) 

At = sampling interval (5 ms in this analysis) 

N = number of samples (512 in this analysis) 

N, = number of squared FFTs summed. 

G = channel gain, including recorder, in V/(A/m). 
Appendix 11. Location Test Data Sheets. 

The following abbreviations are used in the Sensor Data of the Sensor 

Data Unit data tables, in order: 

CHAN - the channel (X,Y, or Z) corresponding to the following 

three entries. 

Amp1 - the displayed signal amplitude in pictoteslas. 

P - the displayed phase in degrees. For a reference channel 

(see below), phase is relative to the SDU clock. For a 

non-reference channel , phase is re1 ati ve to reference 

channel. 

SNR - the long-term signal-to-noise ratio in decibels of the 

individual channel. 

REF - the reference channel of the SDU. This is selected 

automatically according to the strongest signal. 

SNRS - the long-term system signal-to-noise ratio in decibels. 

T - the elapsed time in seconds since system reset. 

PM - the phase difference in degrees between the SDU's 

reference channel and the primary SDU's reference channel. 

SNRS - the short-term system signal -to-noise ratio in decibels. 

T - the low-pass filter time constant in seconds. 
; ==--- ---===a ; 

------ PROJECT NCIME <4 CHAR) I 

: KM02 I I 

DATE & TIME (25 CHAR) 

I-=p----~=~===3,s==r:s=r:===X=========---~t~I 

: OCTOBER 10, 1984 Wednesday P . M. I a 

:,----.----,,,,-------------------------: 

MINE LOCATION (25 CHeR) 

;----------------------===:3:======c==----a - ---------- 

I K-M, HOBBS, NEW MEXICO 8 I 

I 1 

I,-,,-,,,,-,,,,--,----------------------I 

COMMENTS (25 CHAR) I------------------------------------- ,- ------- ---------------------------: 

POSITION 1 - 1000' LOOP 

COORDINFITE SYSTEM BFISIS (225 CHAR) 

;=====E=====I=============3:X:II=I=r=r=====: 

I I 

TRANSLATED MINE COORDINATES • :-------------,-,,,-------------------' 

COORDINATE BFISELINE SIGNCIL PR X MFIRV 

X--AZIMUTH UNITS FREQUENCY SDU 

:==r======: : ====- : : ===a== : : =a=== : I I I a I a I a I I I 

I 9 0 I I F a 10.6 a • B • '--------I ----- ' I ------ I I ----- ' 

(0-360 I)=> <F/M) <HZ) <A/B/C) 

EQUIPMENT SERIAL NUMBERS 

;IIIZ========~=I==:=e======~===========: 

I SDU CS= 1 I SENSOR Flr I 

1 :----------------:--------------------: 

I SDU B: I SENSOR BZ I 4 4 s 

;----------------;--------------------; 

I SDU C= 3 I SENSOR Ct I 

3 a 

;----------------;--------------------: 

SENSOR PLACEMENT DCITfi 

I----3m-----'--I-----j=-,:-------:==l====.; , ---- ,-------I----- 

: SEN X-LOC : Y-LOC : 2-LOC X-AZM : 

:-----;=======;.====~=.==;====4=3;I~=====

a I I 

I A -576.75 50.88 -6.0 144.2 *a 

:-----;-------;-------:-------;-------: 
: ====== : : ====== : 

TIME <HHtMM> : 12~33 I PROJECT : ~~02 I 

I I 

I ------ I 

------ : 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES AREA EQUALS MOMENT 

,; \ I :=======: : ------- --- : I : -:- * I 

4916 --- I 

I ------- : I :-------: ------- : 

< AMPS > <SGI-METERS) < AMPx Mx M) 

SENSOR DATA UNIT A 

*------*----------- I,-----m-----------:--p------;I=------I 

: CHAN : Camp1 <pT> : P <DEE> : SNR I 

:------L:'-----------~---------:---=5----I 

m X : 0.3706 E01 : -172 : 36 I 

:------;-----------:---------:--------: 

I Y : 0.5211 E01 : -171 : 30 m 

I I I . I 

I Z : 0.4616 E01 : 168 : 39 I 

;------:-----------;---------:--------: 

: REF SNRS T PM SNRS T i l I --- I I -- I I -- I a I --- : : ==== : I -- I m -- I I I -,--- I I 

SENSOR DATA UNIT B :=====2::======3====;========3=:========; 

: CHAN : Amp1 <pT> : P <DEG> : SNR m 

:======;====

: REF, SNRS T PM SNRS T: 

: === : I -- 8 I -- I I 8 --- I I I ---- I I I -- I I -- m I --- I I I 

SENSOR DATA UNIT C ------I----------- I-,,,--I-----------D---------:--------D I--------- 

: CHAN : amp1 <pT> : P (DEE) : SNR I 

;======;======a====:=========;======

I X : 0.5000E01 : 178 : 33 I 

:------:-----------:---------:--------: 

I Y : 0.3742 E01 : 111 : 37 I 

;------:-----------;---------;--------: 

I Z : 0.9429 E01 : -6 : 35 8 

. . . I 

: REF SNRS T PM SNRS T: 

: === : I -- I I -- I : === : I I ---- I I -- I I -- I I --- I I I 
I ------ 8 8 I : =====a : 

TIME CHH=MM) : 12:45 8 PROJECT KM02 I 

I I 

I ------ I ------ : 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES ARE& EG2UAl-S MOMENT 

:-------: \ / I-------: 

8 ------- --- : ======= I 

I : -:- : 8 I 8 --- 8 I 4200 I - - - - - - - : :-------: I ---,

: 

CAMPS) C Sm-METERS) CAMPxMxM) 

SENSOR DATA UNIT , 

I --,-,------ :$==========:=========:==----

: CHAN 3 Amp1 CpT) : P CDEG) : SNR I 

I------I-----------I--------- 

, ------ I-----------8---------:--------: ---,-

I Y 1 0.5238 E01 I 

- 173 I 2 8 I 

:------:-----------:---------:----------I 

I Z : 0.4644 E01 I 

- 180 I 44 I 

: ------ ' -----------:---------:--------I 

: REF SNRS T PM SNRS T : 

: === : I 

I -- -- 8 

8 I 

I --- I 

8 : ==== : I I -- I I : === : 

SENSOR D&T& UNIT B :======:===========:=========:====a===

: CHAN Amp1 CpT) : P CDEG) : SNR 8 

I I ------ I-----------:---------:--------: ---,------,,

I X : 0.5566 E01 I -175 I 3 9 8 

: REF. SNRS T PM SNRS T: I --- 8 I 8 I -- I I -- 8 I --,-- 8 I ---- I I ----I I -- I I -- I I I --- 8 

SENSOR DATA UNIT C :------:-----------:---------I--------I I--------* 

: CHAN : Amp1 CpT) : P CDEG) : SNR I 

:------:-----------:---------8--------8 I--------a 

I X : 0.5001 E01 a 179 m 35 I 

: REF SNRS T PM SNRS T : 

: === : 8 -- I I -- 8 : === : I ---- I ----a I -- I I -- 8 I --- 8 8 8 
: ====== : I------: 0 ---

TIME <HH=MM) : 13:00 0 PROJECT i KM02 o 

0 0 

0 ------ 0 0 ------ 0 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES AREA EGZUALS MOMENT ====a== : \ '-------: 0 ------- --- : =I==

: I : -:- 0 I 0 0 --- I : 4900 - - - - - - - : :-------: ' -------: 

< AMPS < SQ-METERS) <CIMPxMxM> 

SENSOR DATFI UNIT A '-=====:===========:=========:========: 8- 

: CHAN : Amp1 <pT) : P <DEB) : SNR o 

:====a=:===========:=========;=======

: REF SNRS T PM SNRS T : 

1 === : l -- 8 8 -- # I --- l 0 0 ----I 0 ---- 8 0 

0 -- -- : : === : 

SENSOR DATA UNIT B :======:===========:====X=====:========: 

: CHAN 1 Amp1 <pT> : P <DEG) : SNR l 

:-----=o-----------o---------o--------: 

I X I 0.5544 E01 0 -175 0 43 I 

:------:-----------:---------:--------o 

I Y 8 0.2814 E01 0 -177 : 38 0 

:------:-----------:---------:--------* 

0 z 8 0.1015 E02 0 159 0 67 I 

:------:-----------:---------:--------' 

: REF, SNRS T PM SNRS T: 

: a==: : I -- 0 0 -- 0 0 --- I l 8 0 ---- 0 0 0 ' -- I l -- 0 : === : 

SENSOR DATA UNIT C , 

0=-----8-----------0---------0--------0 -----I- --------- o---------o--------o 

: CHAN : Amp1 <pT) ! P <DEG) : SNR I 

m------o-----------o--------- --------a 0 ------ 8-----------o---------:--------o 

: REF SNRS T PM SNRS T : 

: === : 0 -- 0 0 -- 0 : === : : E=== : # -- 8 0 0 : === : 
: =I===== : I 

, ----------, I 

TIME <HHtMM) : 13~10 I PROJECT i KM02 I 

I I ' ------ ' I ' ------ 8 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES EIRECI EQUEILS MOMENT 

:-------: \ / :-------' ------ --- : ===a=-,= : 

SENSOR DCSTA UNIT R I------@--------,--I--------, ,,,,,,,,I 

: CHAN : Amp1 <pT> : P <DEG) : SNR I 

I-,----I---,,---,-- # ------ #-----------:---------'--------: --------

I -------- I X # 0.3708 El # -171 I 3 4 I 

;------:-----------:---------:--------I 

w w a a I 

: REF SNRS T PM SNRS T: I ---I --- I I -- I I -- I : === : I ---- # I I I -- I I -- I : === : 

SENSOR DCSTCI UNIT B :======:====

: CHAN : Amp1 <pT) : P <DEG> : SNR I 

........................................ 

m X : 0.5549 El I -175 I 38 I 

:------:-----------:---------:--------: 

# Y : 0.2836 El I -175 a 3 1 I 

:------:-----------:---------:--------; 

l Z : 0.1014E2 I -168 I 57 I 

. . . . : REF SNRS T PM SNRS T: 

SENSOR DATA UNIT C 

: CHEIN : amp1 <pT) : P <DEG) 1 SNR I 

: REF SNRS T PM SNRS T : I --- I I I # -- I I -- I : === : : ===I : I -- I I -- I : ==

: 
TIME CHHzMM) : 13~20 a PROJECT f KM02 8 

I I ------ ------ : 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES AREA EQUALS MOMENT 

;-------; \ / ;=======: --- : ======= : I ; -;- ; I I I --- : 5000 I 

I ------- : : ----: I -,,----: 

CAMPS) CSQ-METERS) (FSMPxMxM) 

SENSOR DATA UNIT A :-----=:;----3---5=--:---------I--,,,-,, I--------; 

: CHAN : Amp1 <pT> : P CDEG) : SNR I 

I------I-,--------,I---------;--a-----l m------,-----------a--------- 

: Z : 0.4635El I -161 I 46 I 

: ------ I-----------:---------:--------' 

: REF SNRS T PM SNRS T : 

: === : I -- I I -- I : === : ; ==== : I -- I I -- I : ==e= : 

:Z: : 32 : : 1170 : : 17 : 43 : : 15 : I 

:---:--:--:--:---:--:----:--:--:--:---: 

SENSOR DATCS UNIT B .......................

: CHAN : emp1 CpT) P CDEG) : SNR 8 

I------1--------,--I--------- I------r-----------l---------:--------I --------I 

I X : 0.5553 El I -175 I 38 I 

:------;-----------;---------;--------; 

I Y : 0.2824 El I -178 I 3 1 I 

;,------;-----------;---------;--------; 

a Z : 0.1013 E2 I -133 I 5 8 I 

I 

;,---.---;-----------:---------:--------; 

: REF, SNRS T PM SNRS T: I --- I I ---a I -- I I -- I a --- I I I I I ---- I I I -- I I -- I I --- I 

SENSOR DATA UNIT C :======:====

: CHAN : Amp1 CpT) P CDEG) : SNR I 

....................................... 

I X : 0.4978 El I 177 I 3 4 I 

I -- m I - --- I 

I Y : 0.3694 El I 6 I 35 I 

I ;:----------;---------;--------: 

I Z : 0.9398~1~ I - 7 I 35 I 

;,------,;-----------;---------;--------: 

: REF SNRS T PM SNRS T : I --- a a -- a I I --- I ; ==== ; I -- I I -- I I --- I I -- I I --- I 
: ==3===3 : : ====== ; 

TIME <HH=MM> :13:30 I PROJECT i KM02 1 

I I 

I ------ I I 

I ------ I 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES AREA EaUAl-S MOMENT 

: ====5=== : \ / :====I==

--- : ------- : I : -:- ; I I I --- rn 4913 I ------- : \ :-------: ' ------- : 

CAMPS > CSGZ-METERS) C GMPx Mx M > 

SENSOR DFITFI UNIT A ------I-----------I---,----- I ------ I-----------I---------:---- ----- : 

: CHAN : Amp1 CpT) : P CDEG> : SNR I 

m------ I------:-----------:---------:--------: --------,-, ----,-----,,,,,

I X : 0.3715 El I -172 I 34 I 

:------'-----------;---------:--------' 

8 . . . : REF SNRS T PM SNRS T : I 

, --- I I -- I I -- I I --- 1 I I I I ---- ----I I a -- a I -- I : === : 

SENSOR DATA UNIT B ....................................... 

: CHAN 1 Amp1 <pT> : P CDEG) : SNR I 

;------;-----------I----,----I-----,,-I 1--------- I--------, 

I X : 0.5547El I -175 I 3 9 I 

;------:-----------:---------:--------: 

I Y : 0.2816 El D -177 a 3 1 I 

I I . . -- m 

I Z : 0.1012 E2 1 - 106 I 56 I 

:------:-----------;---------'--------I 

: REF SNRS T PM SNRS T: I I --- ---, I I -- I I -- I I --- I I I I I ---- I I I -- I I -- I : === ; 

:Z: : 41 : : 1688 : : 0 I : 51 : : 15 : I I '---:--:--:--:---:--:----'--:--:--:---: 

SENSOR DFITA UNIT C ................

: CHCIN 1 Amp1 CpT) : P CDEG) : SNR I 

....................................... 

I X : 0.4976El I 177 I 3 4 • 

: REF SNRS T PM SNRS T: 

: === : m -- I 1 -- s : ===: ; ; ==== : I -- I I I : =3= : 
: =========: a 

------ PROJECT NAME C4 CHAR3 : a 

1 KMBC m-,--,-,,-: 

DATE St TIME (25 CHAR) .................................. 

OCTOBER 10, 1984 Wednesday P.M. 

MINE LOCATION (25 CHAR3 :=============================------==a 

I K-M, HOBBS, NEW MEXICO a 

I I 

'-------------------------------------I 

COMMENTS C25 CHAR) 

;=======

. . i I 

I SENSORS B AND C ONLY I 

'-------------------------------------I 

COORDINATE SYSTEM BASIS (25 CHAR) :=====================E========l=======: 

a TRANSLATED MINE COORDINATES I 

COORDINATE BASELINE SIGNeL PR I MARY 

X-- CIZ IMUTH UNITS FREGIUENCY SDU I--------* 

*--------I ; ===== ; ; ====== : ; ===== : 

EQUIPMENT SERIAL NUMBERS ;================:===I==========

I SDU 43: 4 • SENSOR AS I 

4 :----------------:--------------------: 

I SDU B= 3 I SENSOR B: I 

3 ;----------------:--------------------: 

a SDU C: 4 I SENSOR C: I 

4 ;----------------:--------------------: 

SENSOR PLACEMENT DATA 

I-----I-------I-------:-------a-------l , ------- 

: SEN X-LOC Y-LOC : Z-LOC : X-AZM : I----- -------I--,---- ------- -------I 

I a -128.57 308.62 I I I -3.0 : 151.0 

:-----:-------:-------:-------:-------: 

I a I rn 295.67 : 552.18 0.0 : 147.5 

;--.---.;-------;-------:-------:-------: 

I C I : -128.57 I : 308.62 I : 151.0 -3.0 :-----;-------:-------:-------:-------: 
: ====I= : : ===-,I= : 

TIME <HH:MM) 1~~45 a PROJECT KMBC a 

I I 

I ------ a --L--- : 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES ARECI EQUALS MOMENT I-------: I ------- \ / :------- : --- : ======= ; 

SENSOR DCITA UNIT A ....................................... 

: CHAN : emp1 <pT> ! P <DEG> : SNR I 

I------*-----------;---------;--------I I------#----------- 

I X a 0.5566 El ! -175 a 3 9 I 

:------'-----------;---------;--------: 

a Y I 0.2836 El a - 178 a 3 3 I 

;------:-----------;---------;--------; 

I z I 0.1016 E2 a 105 a 5 3 I 

I 

: -:-----------;---------;--------: 

: REF SNRS T PM SNRS T : 

; === ; I -- I a -- I I --- a : ==== ; I -- a I -- a : === ; 

:Z: : 42 : : 710 : a -0 : : 53 : : 15 : I a a I a a I I a :---:--s--@--'---'--'----@--a--'--m---' I 

SENSOR DATCS UNIT B ....................................... 

: CHAN : Amp1 <pT> 8 P <DEG> : SNR a 

I-,----#----------, I------I-----------:---------:--------: --------- ----

I X • 0.5001 El a 179 a 35 I 

;------:-----------;---------:--------; 

I Y a 0.3726 El a 157 a 38 I 

:------;-----------;---------;--------: 

a Z : 0.9430El a - 5 a 37 I 

:------:-----------;---------;--------: 

: REF SNRS T PM SNRS T : a --- a I a I -- I I -- I a --- a I a a 

, ---- ----I a I -- I a -- a : === : 

SENSOR DATA UNIT C 

#------ I----- :----------- -----------:---------:--------a --------- --------I 

: CHAN Amp1 <pT> : P CDEG> : SNR I 

:------;-----------:---------@--------a 

: REF SNRS T PM SNRS T : I I --- ---, a I -- I a -- I : === : : =3== : I -- I I -- a : === : 
:=========I 

------ PR03ECT NAME (4 CHAR) : KMCA I 

I 

I---,,-,--: 

DFITE & TIME (25 CHAR) ;=======-======================-------I 

I OCTOBER 10, 1984 Wednesday P.M. I 

m I '-------------------------------------' 

MINE LOCATION (25 CHfiR) ................................................. 

I K-M, HOBBS, NEW MEXICO m 

m I 

m-------------@ 

COMMENTS 2 CHAR) ;====================5=--=================; 

m I 

l SENSORS A & C a 

@-------------------------------------I 

..

COORDINATE SYSTEM BASIS (25 CHAR) 

I I 

m TRANSLATED MINE COORDINATES - m 

'------------------------------------L' 

COORDINATE BASELINE SIGNCIL PR I MCIRY 

X--AZIMUTH UNITS FREGIUENCY SDU #--------I 

, -------- ; ====--, ; : ====== : I ----- I I -----I 

EQUIPMENT SERIFIL NUMBERS ---------------- I----------------:--------------------I --------------------I 

I SDU A: 1 l SENSOR fir 1 I 

;----------------:--------------------' 

l SDUB: 3 I SENSOR Br 3 8 

m SDU Cm 3 I SENSOR Cr 3 I 

SENSOR PLACEMENT DATA ....................................... 

: SEN : X-LOC Y-LOC Z-LOC X-AZM : ....................................... 

m CI : -576.8 : 50.88 I -6.0 I 90 l 

;-----:-------;-------:-------;-------; 

m B 295.7 : 552.20 I 0.0 I 9 0 m 

m-----;-------;-------:-------:-------: 

l C : 295.7 : 552.20 I 0.0 I 90 I 

;------,;-------:-------;-------;-------; 
; =a==== : : ====== ; 

TIME <HH=MM) : 12:45 1 PROJECT KMCA 1 

1 1 

I ------ -,,,,- : 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES ARECI EGZUFILS MOMENT ,,,

------- \ / I-------I 1 -------a --- : ===

; 

SENSOR DATA UNIT CS I-,,---l-----------l---------;==---,-,; #------I-----------*--------- 

: CHeN : Amp1 <pT) : P <DEG> : SNR I 

:------~===========::=====Z====:========; 

a z I 5.434 1 0 I 44 1 

I------:-----------;---------:--------: 

: REF SNRS T PM SNRS TI : 

: === : 1 -- 1 1 --- 1 1 -- I I -- 1 1 --- : a=== : 1 -- 1 : === : 

:Z: : 31 : : 590 : a 0 : : 44 : : 15 : I I I 1 I I I I 1 

:---:--I--~--a---l--m----I--I--a--l--- - : 

SENSOR DfiTCS UNIT B l-,-l-l 1---------#-------- 

: CHFIN : FImp1 <pT) : P CI1)EG) : SNR I 1 

l---,--I-----------l---------l--------l ------ 1-----------1---------*--------1 

I X 1 0.5520 I 0 I 3 5 1 

1 

:------:-----------:---------;--------: 

I Y a 7.546 1 0 1 38 I 

: REF, SNRS T PM SNRS T: I 1 --- I 1 -- I 1 -- 1 I --- 1 1 1 1 ---- 1 1 1 -- I 1 -- I : === : 

;Y: : 36 : : 819 : : 0 : : 45 : : 15 : 1 a 1 s 1 1 1 1 I 1 1 

l---:--l--*--m---l--*----m--a--l--l---l - - 

SENSOR DCSTFI UNIT C ;----,-,-,1,--,-,-,1 :3=X=I==:=========== --------- l--------l 

: CHAN : Amp1 <pT) : P CDEG> : SNR 1 

: REF SNRS T PM SNRS T : I I --- 1 1 1 -- 1 : --- I I ---- 1 1 I 1 -- 1 1 -- I 1 -- I : === : 
------ PROJECT NAME <4 CHAR) : 

! KMAB 

DATE S TIME <25 CHfSR) :=~=a================r=============-----a 

a a 

a I OCTOBER 10, 1984 Wednesday P.M. I 

a--_----------------------------------a 

MINE LOCATION (225 CHAR) :=====================================a 

I a a K-My HOBBS, NEW MEXICO -------------------------------------: 

COMMENTS (25 CHAR) a,-----,--

-------------------------------------: 

a a 

a a SENSORS A & B ONLY a a-------------------* 

COORDINCSTE SYSTEM BASIS (25 CHAR) :=========================r======-----: 

a 

a TRANSLATED MINE COORDINATES 

COORDINATE BFISELINE SIGNAL PR I MARY 

X-- AZIMUTH UNITS FRE1;7UENCV a ----,,,- a ------ a 

SDU #--------; : ===== ; ------ : ===--,=, :

EmUIPMENT SERIAL NUMBERS 

:---------------- -=.--=-------------==:a 

a SDU A: 1 a SENSOR A: 1 a 

a SDU Bs- 4 a SENSOR B: 4 a 

a SDU Cr 4 a SENSOR C: 4 a 

SENSOR PLACEMENT DATA a-----a-------a,,-,,--a-

----- a-------a-------a-------'-------; ------- 

: SEN : X-LOC : Y-LOC : Z-LOC : X-AZW : 

:=====;=====
; ====== ; : ====== a 

TIME <HH=MM) : 12:41j I PROJECT I KwB I 

I I I ' ------ I I ---,

: 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES AREA EaUALS MOMENT 

;-------; \ / ;=======; --- : ======= I 

I : -;- : I I a --- a I 4800 I ------- : :-------: I --,-

: 

< RMPS ) CSQ-METERS) CAMPxMxM) 

SENSOR DATA UNIT A I------.-----------I,-,------I---- '------I----------- I---------I--------; 

: CHAN : Amp1 CpT) i P CDEG) : SNR I 

a------I-----------;---------;----2-3-: I ------ I----------- 

I Y a -0.0262 a 0 I 28 I 

;------;-----------;---------;--------I 

I z I 5.434 I 0 I 4 4 8 

:------;-----------;---------;--------I 

: REF SNRS T PM SNRS T-: I --- I I -- I I -- I : === ; ; ==== ; I -- 0 I -- I I -,- I I --- I 

SENSOR DCSTCS UNIT B ....................................... 

: CHAN : CSmp1 CpT) : P CDEG) : SNR a 

I I-----------:---------:--------; ,--,----,-,

8 X I -6.212 I 0 I 3 9 I 

I 

;------;-----------;---------;--------* 

I Y I 4.207 I 0 I 33 I 

8 

;------;-----------;---------;--------I 

I z : 12.20 I 0 I 53 I 

:------;-----------'---------;--------I 

: REF, SNRS T PM SNRS T : a --- I I I I -- I I -- 1 : === : : ==== ; I -- I I -- I I --- I I I 

I I I I I I I I I : Z : 42 : 710 ! a 0 : :53 : : 15 : 

'---'--'--'--'---'--a----'--m--'--'---8 

SENSOR DATA UNIT C 

:===-==;==I==

: CHFIN : Amp1 CpT) P (DEB) : SNR I 

;------;-----------;---------;--------; 

: REF SNRS T PM SNRS T : 

: === ; I -- * I -- I I --- a I ---I I I ---- ----I I I -- I I -- I : === : 
:=====I==

------ PROJECT NAME (4 CHAR) : a 

a KMN R 

'---------a a 

DATE Sz TIME (25 CHAR) 

:===========,========I-=============-------: 

a OCTOBER 10, 1984 Wednesday P.M. a 

I a '----,---------------------------------a 

MINE LOCATION (25 CHCIR) :==================================---a 

I a 

a K-M, HOBBS, NEW MEXICO I 

I-------------------------------------' 

COMMENTS (25 CHAR) 

a 

a NO ROTATIONS FROM BASELINE a 

a-------------------------------------a 

COORDINATE SYSTEM BASIS (25 CHAR) 

;=-===================================: 

a a 

a TRANSLATED MINE COORDINATES - I 

a-------------------------------------a 

COORDINCSTE BASELINE SIGNCSL PR I MARY 

X--AZIMUTH UNITS FREQUENCY SDU 

:========: : ===== ; ; ====== : : ===== 

EQUIPMENT SERICIL NUMBERS 

:================;====================; 

a SDU A: 1 SENSOR A: 1 a a 

:----------------:--------------------I 

a SDU B: 4 SENSOR B: 4 a a 

-. ;----------------:--------------------a 

a SDU Cr 3 SENSOR C: 3 a 

SENSOR PLACEMENT DATA a-----a-------a-------a------- -------a I-------,------- 

: SEN 1 X-LOC : Y-LOC : Z-LOC : X-AZM : m-----a-------a------- a-----a-------,a-------:-------:-------a ------- -------I 

a A : -576.75 -6.0 : 150.1 a 50.88 a I 

;-----;-------:-------:-------:-------: 

a B : -128.57 : 308.62 -3.0 : 150.1 a I 

;-----:-------:-------:-------:-------; 

a C : 295.67 : 552.18 0.0 : 150.1 a a 

:-----a-------;-------:-------:-------; 
I I ------ ------I I : ====== I 

TIME <HH=MM> : 12:45 I PROJECT i KMNR 8 

I I 

I ------ I --,,,: 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES AREA EmUAl-S MOMENT 

; ======= : \ / ;=======: --- : =a===.== I - 

: ; -;- : I 

--- I I 

• I 4200 ' ------- : 0 :-------: I ----

: 

C AMPS > < SQ-METERS > CAMPxMxM) 

SENSOR DCITA UNIT A 

:=====C==;=======r====;=========:==------m 

: CHAN : Amp1 <pT> : P CDEG) : SNR I 

....................................... 

: REF SNRS T PM SNRS T : I 

, --- I I -- I I --- I I -, I a -- I I ---I : ==== : I -- I I ,-, --- 

SENSOR DATA UNIT B I------ I------;-----------:---------:--------; ----------- -- ----

: CHAN : Amp1 <pT) : P <DEG> : SNR I 

I------.----------- --------- ---,--,I 

I X 0.5566 E01 I -175 I 39 I 

:------;-----------:---------:--------a 

I Y I 0.2836 E01 I -178 I 3 3 I 

:------:-----------;---------;--------I 

I Z : 0.1016 E02 I 105 I 53 I 

m rn I I I 

: REF, SNRS T PM SNRS T: I --, I I --- I -- l I -- I I ---I 

I --- I I ---- I I ----I : == : : === : 

:Z : : 42 : ! 710 : -0 : : 53 : : 15 : I 

I I I I I I I I I I I 

'---'--m--'--a---'--'----'--'--'--'---: - 

- SENSOR DATA UNIT C 

:======:====

: CHAN : Amp1 <pT> : P CDEG) : SNR I 

I---,--I,-,-------- --------- --------I 

I X : 0.5001 E01 I 179 I 35 • 

: REF SNRS T PM SNRS T : 

: === : I -- -- I 

a : ==a ; : ==== : a I -- I I I I --- --- , 8 
------ PROJECT NAME <4 CHAR) : m 

1 KMC R I----,----: 

DCITE St TIME <25 CHCIR) m----------r------------------m .................................. 

OCTOBER 10, 1984 Wednesday P.M. 

MINE LOCATION (25 CHaR) 

;-------==s=====E====3=====5=======---m 

I K-M, HOBBS, NEW MEXICO 1 

l ~,--,,,---,---------------------------: 

COMMENTS <25i CHFIR) 

COMPASS READING FOR AZIM 

COORDINCITE SYSTEM BASIS (25 CHAR) - 

........................

TRANSLATED MINE COORDINATES 

COORDINATE BCISELINE SIGNCIL PRIMARY 

X--FIZIMUTH UNITS FREGtUENCY SDU :=======a: : ===E= : : ====== : I ---

---- I 

EQUIPMENT SERICIL NUMBERS 

I SDU Cb: 1 1 SENSOR CI: I 

I -- -- -- 

I SDU BP 4 

m - 

I SENSOR Bz A 

. - . . I SDU Cr 3 SENSOR C: 3 I I 

:----------------;--------------------; 

SENSOR PLACEMENT DCITA 

:-----:-------:-------:====-,==: 

: SEN X-LOC : Y-LOC : Z-LOC : :-----;-------.-------l-------m -----#-------I 

-,--

--c---- m 

X-AZM 

------- l 
I ------ 

--c--- I 1 : ------ I 

TIME <HH=MM) : 12~45 a PROJECT i KMCR a 

I I 

I ------ I ------ : 

EXPECTED EXPECTED EXPECTED 

CURRENT TIIMES CIRECI EG!UALS MOMENT :------3: \ / :=======:: --- : ======= : 

SENSOR DCITA UNIT G :====E=:==s=e===s=e=:=======~=;=====--==I 

: CHCIN : amp1 < : P CDEG) : SNR I 

I------I----------- ------ ,-- --------:---------:--------I --------- --------I 

I X I 0.3750 E01 I -170 I 

I 34 I 

;------:-----------:---------:--------m 

I -- I I . : REF SNRS T PM SNRS T- : 

: === : I -- . I --- I * ---I : ==== : I ,- I I -- I I -- I : === : 

SENSOR DeTA UNIT B ....................................... 

: CHAN : 6mp1 <pT> : P <DEG> : SNR I 

:====E=:========CL==:========E=:I==E====: 

I X I 0.5566 E01 I -175 I 3 9 I 

: ------ -----------:---------:--------: ' I Y rn 0.2836 E01 1 -178 I 33 I 

:------:-----------:---------:--------I 

I I I I • Z s 0.1016 €02 I 105 a 53 I :------:-----------:-------&-:--------' 

: REF SNRS T PM SNRS T : 

: === : I -- I : === : : ==== : I -- I I -- I I -- I : === ; 

:z: : 42 : : 710 : : -0 : : 53 : : 15 I 

I I I I I I I I 

I---:--:--:--:---'--.----'--'--'--.---a - 8 - 

SENSOR DATA UNIT C :======:===========:=========:===s

: CHAN : Amp1 <pT> : P <DEG) I SNR I 

:.====E.=:===========:=========:========: 

I I I I I • X 0.5001 E01 179 35 

:------:-----------:---------:--------: 

I Y I 0.3726 E01 I 157 I 38 I 

I 

:------:-----------:---------:--------: 

I I I I I I Z I 0.9430 E01 I - 5 37 

:------:-----------:---------;--------: 

: REF SNRS T PM SNRS T : I 

, ---a --- I -- I I --- I I ---- I I ---- I I -- 

I -- I I --- I I -- I I --- I I --- I 

: Y I 36 : 819 : -43 : : 45 : : 15 I 

I I I I I I I 

'---:--'--:--8---m--*--_-I--8-_'--a---' 
I---------, 

'---------I 

------ PROJECT NAME (4 CHAR) : 1 

a KM03 s---------: 

DeTE St TIME (25 CHAR) :S=P======~===5~========:============----I 

I I 

a 

I OCTOBER 10, 1984 Wednesday P.M. I 

I ---------------------------------@ 

MINE LOCATION (25 CHCtR) :----=====s==I==============I 

I I 

I K-M, HOBBS, NEW MEXICO rn 

'-------------------------------------l 

COMMENTS (25 CHAR) ;=================L-==S==========; 

I I 

I 

I POSITION 2- 480' LOOP I 

,-----,-,-----,,-,---

COORDINCSTE SYSTEM BCISIS (25 CHAR) 

;=========s================C-=====-========

m I 

I TRANSLATED MINE COORDINATES - 8 '-------------------------------------' 

COORDINCSTE BASELINE SIGNFIL PR I MARY 

X-- FIZ XMUTH UNITS FREQUENCY SDU 

;======a=: : ===== I I ------ ------I I I ----- I a I 

EGlUIPMENT SERICIL NUMBERS 

:=========s==I==E;=========l=====E====: 

SDU FI: 1 a SENSOR A: 1 I 

:----------------:--------------------I 

I SDU B: 4 I SENSOR B: 4 I 

I - ;----------------;--------------------: 

s SDU Cr 3 I SENSOR C: 3 I 

SENSOR PLACEMENT DCSTA 

;----=:;-------;=------:===----:==~====: 

: SEN X-LOC Y-LOC : Z-LOC : X-AZM : 

;-----:-------;-------:------=I=======: 

I A I -576.75 I 50.88 : -6.0 144.2 I 

:-,---,-;-------;-------:-------:-------: 

I B I : -128.57 308.62 : -3.0 : 151.0 I 

:.----.-;-------:-------:-------;--------: 

I C I 295.67 I 552.18 : 0 : 147.5 I 

:.------'-------:-------;-------;-------: 
; ====== : ; ------ I 

TIME <HH=MM) : 13:45 I PROJECT : ~~03 m 

I m I I ------ I I ------ 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES AREA EGlUALS MOMENT 

:-----==; \ 1 ;=======: --- I I -,,,,,, ------- : 

SENSOR DATFI UNIT CI :------~=====3====1==;=========;=-------; 

: CHAN : Amp1 <pT) : P <DEG) : SNR I 

:------:=I=====

I Z : 0.3030 El -65 : 46 I 

;------:-----------;---------:--------a 

: REF SNRS T PM SNRS T .: 

: ==3: : m -- I m -- m --- m 

m : =a== : I -- m m -- m : === ; 

SENSOR DATA UNIT B ....................................... 

: CHAN : Amp1 CpT) P CDEG) : SNR I 

........................................ 

I X 0.1142 EO : -155 : 12 ;------:-----------m---------:--------m 

m Y : 0.1197 El : 6 : 20 a 

. . . I 

m Z : 0.1742 El : 40 : 54 

;------;-----------:---------:--------; 

: REF, SNRS T PM SNRS T: 

: === ; I -- I m -- ; === : : ==== : I -- m I -- I : === : 

:Z : : 25 : :I25 : : -0 : 34 : : 15 : 

:---:--:---:--:---:--f----:--:--:--:---: - 

SENSOR DATCI UNIT C 

;=====3: ;,---,---,--I----,---,.,--,,-,,. -----------,---------,--------I 

: CHeN : amp1 CpT) : P CDEG) : SNR m 

.......................

X : 0.1457 E-1 : -133 : ** 

;------;-----------;---------:--------; 

I Y : 0.9325 EO : -98 : 21 8 -- 

-- - - I I -- 8 

m Z : 0.5173EO : -16 : 33 I 

;------:-----------:---------'--------; 

: REF SNRS T PM SNRS T : 

; === : -- m I -- m : ==I : I I ---- m m -- I I -- I ; === : 

:Y : : 20 : :I71 : : 142 : 33 : : 15 I 

I I m m I I I I m I I I 

m-_-m--'--m--'---'--m----m--'_-*--'---m 
; ====== : I --,-

TIME CHH:MM> : 13:55 I PROJECT : ~03 8 

I I I 

I ------ I 

I 

I ------ I 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES AREFI I ----,-- 

EG!UCSLS MOMENT 

I ------- ; \ / ;=======: --- : ======= ; I ; -;- * I : 900 I --- I 

I ------- : \ :-------: a -------: 

C FIMPS > C SQ-METERS > C AMPx Mx M 

SENSOR DATFI UNIT A 

:======:===========:=========:========; 

: CHAN : Amp1 CpT> : P CDEG) : SNR I 

:======:===========:=========:========:. 

8 X : 2280 EO : -171 : 9 I 

;------:-----------;---------:--------I 

8 Y : 6969E-1 -132 : -7 I 

:------;-----------:---------;--------I 

8 Z : 3004El : -57 : 40 . I :------'-----------;---------;--------' 

: REF SNRS T PM SNRS I -- 8 I --- I 

T : 

: === : 8 -- I I --- I : ==== : : =a : I --- 8 

:z : : 25 : : 624 : : 136 : 40 : : 15 I I 

:---:--:--:--:---:--:----:--:--:--:---: 

SENSOR DATA UNIT B :------:-----------I---------;-------,=.I 

: CHAN ! Amp1 <pT> : P CDEG) : SNR • ------.----------- ---,----

,--

8 X : 1569 ED : 172 6 I 

:------:-----------;---------;--------I 

s Y : 1201 El : 7 : 22 I 

:------:-----------;---------;--------I 

: REF SNRS I --- 8 

T I I -- l 8 -- I I --- I s I 

PM SNRS T: I I ------ , I I -- I I -- I I 

, --- ---I I 

SENSOR DATA UNIT C 8 8-----------:---------:--------8 --------- ,--,I 

: CHAN : Amp1 <pT> : P CDEG) : SNR I 

I------8----------- I-----I-----------:---------:--------, -------- ------,-I 

: REF SNRS T PM SNRS T : 

: === 8 -- I 8 -- I I I --- I : ==== : I -- I I -- I I --- I I I 
:=====--==: 

------ PROJECT NAME <4 CHAR) : KM04 I 

a 

I------___a I 

DATE TIME (25 CHAR) I-------------------------------------. I------------------------------------, 

a I 

I OCTOBER 11, 1984 Thursday A.M. I---------------------------------- I 

I 

MINE LOCATION <25 CHAR) ....................................... 

I I 

I K-M, HOBBS, NEW MEXICO a m-------------------------------------. 

COMMENTS C25 CHAR) ....................................... 

I I 

• PCSITION 3 - SMALL 400' LOOP m '-,,,-,----------,,-------------------. 

COORDINATE SYSTEM BASIS C25 CHAR) :===================5==================: 

I I I 

I TRANSLATED MINE COORDINATES a I-------------------------------------' 

COORDINATE BASELINE SIGNFIL PR I MARY 

X--AZIMUTH UNITS FREGIUENCY SDU 

:========: : ===== : I ------ I : ===== : 

EQUIPMENT SERIAL NUMBERS ....................................... 

I SDU A: 1 SENSOR A: 1 I a 

:----------------:--------------------I 

I SDU B:- 4 SENSOR B: 4 I I 

:----------------;--------------------* 

I SDU C: 3 SENSOR C: 3 I 

SENSOR PLACEMENT DATA I-----*------ a:-------'------- -------I 

: SEN : X-LOC 1 Y-LOC : Z-LOC : X-AZM : :-----;---=---;-------a-------1-------a n-------m-------a 

I A : -576.8 a 50.88 I -6.0 a 144.2 * 

:-----;-------:-------:-------I-------: 

I B : -128.6 * 380.60 I -3.0 I 151.0 a 

I 

:-----:-------:-------:-------:------- : a C 295.7 I 552.2 I 0.0 I 147.5 a 

I 

:-----;-------:-------:-------:-------: 
TIME <HH=MM> :10:50 I PROJECT : ~~04 I 

I 8 I ------ ------ : 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES AREA EGZUALS MOMENT 

\ / ;=======: --- I ---,

------- I 

I : -:- : I : 700 --- I 

I 

1 ------- : 1 :-------: ------- : 

CAMPS > < Sa-METERS) ( AMPxMxM) 

SENSOR DATA UNIT A I------ ----:-----------;--------- ----------- ---------I--,.-,,,,I I--------* 

: CHAN : Amp1 <pT> : P CDEG) : SNR 1 I

;======;===========:;=========;========: 

I X : 0.4353 EO : -123 : 23 I 

:------;-----------:---------;--------a 

I Y : 0.9589 EO : -1 : 17 I 

;------;-----------:---------;--------; 

I Z : 0.1073 El : 163 : 15 I 

;------:-----------:---------:--------' 

: REF SNRS T PM SNRS T -: 

: === I -- a I -- I : === : I ,-,, I I ---- I I -- I I -- I I --- I I I 

:X: : 15 : :I19 : : 176 : 19 : : 15 I I 

I I I I 

:---:--:--'--m---'--I----@--I--a--~--_' 

, I I I I 

SENSOR DATA UNIT B ;------:-----------;---------I--------I I--------# 

: CHfiN : Amp1 <pT> i P CDEG) : SNR I 

l------I-----------I---------I--------I 

, ------ ,-----------I--------- #--------I 

, X : 0.5946. EO : -175 1 LL • ;------;-----------'---------:--------' 

I Y : 0.2020 EO : -174 : 14 I ;------;-----------'---------:--------' 

I Z : 0.1956 El : -134 : 55 I 

I I I rn w 

: REF SNRS T PM SNRS T: 

; === : 1 -- I I I --, ---, I I ---- I I 1 I -- I I -- I I --- I I -- I I --- I 

:Z: : 29 : :I70 : : 0 0 : 43 : : 15 I 

I I I I I I 8 I I 

:,---,:--:--'--I---.--'----'--n--a-_a-_-m 

SENSOR DATA UNIT C :------;-----------I---------I--------I ,---------'--------I 

: CHCSN : CSmp1 <pT> : P <DEG> : SNR I 

I------~-----------I--------- --------I 

I 8 1 X : 0.4431 EO : -177 : 13 

;------:-----------;---------;--------: 

, Y : 0.8140 EO : 7 : 22 I 

:------;-----------'---------;--------; 

I I I Z : 0.1428 El 1 34 : 40 0 

;------;-----------I---------:--------: 

: REF SNRS T PM SNRS T : 

: ; I -- I I I --,-- I I ---- I I I I ,- I I -- @ I --- I I -- I I --- I 

:Z: : 23 : :207 : : -1 70 : 40 : : 15 I I 

I I :---:--:--:--m---:--:----~--:--:--:---: 
; ====== : : ===a== : 

TIME <HH:MM> : 11:~~ I PROJECT : ~04 I 

I I I 

I ------ I --,-: 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES AREFI EQUALS MOMENT 

: ======= ; \ 1 ;=======I I ----

I --- , ------- I 

: ; -:- 1 I : 700 --- I 

I I ------- : 1 :-------: ------- I 

I 

<AMPS > < SQ-METERS > < AMPxMxM) 

SENSOR DeTFI UNIT G+ I------I-----------:---------:--------I I ------ I----------- I 

: CHAN : Amp1 <pT> : P <DEG> : SNR I 

:======:===========:=========:========; 

I X : 0.4795 EO : -148 : 17 1 

;------;-----------'---------:--------I 

I Y : 0.8883 EO : 23 : 13 I 

;------I-----------:---------:--------; 

I Z : 0.1060 El -172 : 15 

:------:-----------;---------:--------; 

: REF SNRS T PM SNRS T : 

; === : I -- I I -- I I I --- I I I ---- I I I -- I I -- I : === : 

:X : : 14 : : 933 : : -146 I : LO : : 15 : I 

I I I I I I I I I 

:---I--'--'--'---I--'----'--I--'--'---m 

I 

SENSOR DATFI UNIT B ....................................... 

: CHAN : Amp1 <pT> P <DEG> : SNR I 

;------:------=----I---------I--------* I--------- I--------I 

: REF SNRS T PM SNRS T: 

: === : I -- a I -- I I * --- I I ---- I 1 I I -- I I -- I I --- I I I 

z I :26 : 977 : :O : 40 : : 15 I I 

I 

:---I--'I--'---'--*----8--a--n--a---n 

I I 

SENSOR DATFI UNIT C 

:====== :,-----,,--,I-,,,,,,,-l--------I ----------- #---------#--------I 

: CHFIN : Amp1 CpT) P <DEG> : SNR I 

I------:-----------;---------;--------; 

I ------ 

I Y : 0.7974 EO : 7 : 22 

;------;-----------;---------;--------: 

I Z : 0.1432 El : 99 : 44 I 

:------:-----------:---------:--------: 

: REF SNRS T PM SNRS T : I --- I 1 I -- I I --- I ; ==== : I -- I I --- I I -- I I --- I I -- I I --- I 

: z I : 24 ! :lo13 : : 157 : 40 : : 15 I I 

I I I I I I I I I I I I 

I--_~--'--~--'---'--I----a-_I--I--a---m 
; ==ex== : : ==

; 

TIME <HH:MM> : 11~25 I PROJECT : ma4 I 

I I I 

I ------ I ------ : 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES AREll EG!UAI-S MOMENT 

: ====-== : \ f '-------: a ------- --- : ==

; I ; I I : 700 --- I 

I I ' - - - - - - - : :-------: a ------- I 

< fiMPS) C SQ-METERS > CAMPxMxM) 

SENSOR DllTA UNIT A 

a-3----a-----------I---------I--,-,,-,, I- ----I-----------,--------- I--------: 

: CHAN Amp1 <pT> : P <DEG> : SNR I 

I------*-----------;---------;--------. ,------I----------- I 

a X : 0.4876 EO : -159 : 18 I :------'-----------;---------:--------' 

I Y : 0.8893 EO 10 : 13 I 

:------.-----------:---------;--------I 

a Z : 0.1065 El : -170 : 16 I 

;------:-----------;---------:--------I 

: REF SNRS T PM SNRS T : I ---I 

I --- m I -- I a -- I I --- I I a I ---- I I I I -, I a -- a : === : 

: X I : 15 : : 2156 : : -87 a : 19 : : 15 : a I I I a I a s I 

~---:--'--'--'---'--:----'--'--a--'---: 

SENSOR DATA UNIT B 

;======:===========:=e========;========; 

: CHeN : Amp1 <pT> : P <DEG> : SNR I 

................

I X : 0.6283. EO : -179 : 19 • :------:-----------'---------:--------' 

a Y : 0.2017 EO : -178 : 10 I 

:------:-----------:---------:--------; 

a Z : 0.1946 El : -57 : 49 I 

m a a s I 

: REF, SNRS T PM SNRS -r: 

: === : a -- I I I --- I ---- I I -- I I -- I : IF--- I I -- a : === : 

:z : : 27 : : 2196 : : 38 ; ; 15 ; I I a I I I a a I a a 

a---'--'--'--'---'--'----a--a--a--'---~ - 

SENSOR DllTA UNIT C ....................................... 

: CHAN : Amp1 <pT> : P CDEG) SNR I 

:------;-----------;---------*--------a #--------I 

: REF SNRS T PM SNRS T 1 

: === ; a -- a I -- s : === : a I ---- ----I I s -- I I -- I : === : 

:Z : : 25 : : 2237 : : 107 : 37 : : 15 I a 

a I I a I I I I I I '---'--'--'--~---.--:----'--'--~--'---: 
TIME <HH:MM) : 11:40 I PROJECT : ~~04 I 

I I I 

l ------ I l --,-: 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES AREA EQUALS MOMENT 

;-------: \ / .-------I 

I ------- 8 I ------- I --- I 

c AMPS > c ~~-METERS > CCIMPXMXM) 

SENSOR DeTA UNIT FI , I------.-----------'---------:--------,-, -----,-----------,--------- I 

: CHAN : Amp1 CpT) : P (DEG) : SNR 8 

:=-----;-----------I---------#--------. ----------em--------- 

I X : 0.4898 EO : -171 : 19 • 

:------:-----------:---------:--------I 

I Y : 0.8891 EO : -7 : 13 a :------:-----------:---------;--------' 

I Z : 0.1063 El : -173 : 16 I 8 

I--- - 8 8 8 8 

: REF SNRS T PM SNRS T : I --- I 8 I I -- I I -- I I --- a 8 I a ---- ----a I -- a I -- I ; ==i= : 

SENSOR DATe UNIT B ......................................... 

: CHAN : Amp1 CpT) : P CDEG) : SNR I 

......................................... 

I X : 0.6286 EO $ 175 : 19 I 

------;-----------:---------;--------: 

8 Y : 0.1984EO : -179 : 10 I ;------:-----------' *---------:--------' I Z : 0.1944 El : -23 : 47 I 

8 8 8 # 8 

: REF. SNRS T f=M SNRS T 1 I ---a ---, I -- I I -- . I I --- ---I I I I ----I-- I I -- I I -- I I --- I 8 # 

SENSOR DATA UNIT C 

:======:===========:=========:======== : 

: CHeN : Amp1 CpT) : P CDEG) : SNR a 

:------:-----------:---------I--------' I--------@ 

: REF SNRS T PM SNRS T : 

: =1= : I -- I I -- I I --- I I I I I ---- I 8 a -- a I -- # I ---,

I 

:Z: : 25 : : 3125 : : 70 I : 40 : : 15 : a a I a I I I I I I a I 

'---8--'--I--'---'--'----'--'--'--'---' 
: =====I : ; ==------ I 

TIME <HH:MM> : 11:55 I PROJECT : KM04 I 

I I 

I ------ I 

I 

------ : 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES AREA EQUALS MOMENT 

:====--,=a: \ / :====i==

--- : ------- -------, I 

I : -:- : I --- I I 

a m 700 I ------- : I :-------: I ------- : 

< AMPS > <SQ-METERS) CFSMPxMxM> 

SENSOR DATA UNIT A 

. -- 

: CHAN : Amp1 <pT> : P <DEB> : SNR I 

I----rc-I-----------I-----,---;------I-I I---- -I----------- I--------- I 

w I • X : 0.4908 EO 2 -174 : 19 w --- - w . 

I I Y : 0.8860 EO 1 -3 : 14 I ;------;-----------:---------:--------' 

I Z : 0.1061 El : 175 : 16 I 

;------:-----------;---------:--------u 

: REF SNRS T PM SNRS T : I --- I I -- I ; === ; I 

, ---- I I -- I 

I --- I w -- I I -- I : ==e= : 

;X : : 15 ; : 4082 : : 10 I : 21 : 15 : W I I I I I I I I 8 I '---'--'--'--'---'--'----'--'--'--'--- : 

SENSOR DATA UNIT B ....................................... 

: CHAN emp1 <pT> : P <DEG> : SNR I 

I------I-----------I-----,---I------,-I ,------I----------- I--------- I--------, 

a I I X : 0.6261. EO : 175 : 19 

:------;-----------;---------:--------: 

: REF, SNRS T PM SNRS T: I --- I I -- I : === : , 

I ---- ----I I I -- I a -- I I --- I 

I --- I I -- I I --- I 

SENSOR DATA UNIT C 

;======:==a=====--,==:=========:=======

: CHllN : Amp1 <pT> : P CDEG) : SNR I 

........................................... 

I Y : 0.7929 EO : 8 : 23 I 

:------:-----------;---------:--------: 

I Z : 0.1425 El : -3 1 43 I 

:------:-----------:---------:--------: 

: REF SNRS T PM SNRS T : 

: ===r : I -- e : === ;- I ---- I I I I -- I I -- * I --- I I -- a I --- I 

: z I : 26 : : 4281 : m : 39 : : 15 I 

I : 20 I 

I I I I I I I I I 

'---:--'--:--:---.--.----'--'--'--'---a 
I ------ I I 1 : ====== : 

TIME <HH:MM) : 12:10 1 PROJECT : KM04 8 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES 6REA EQUALS MOMENT I-------* I------ I \ / ;=======: a ------.- I --- I ------- I 

a ; -:- : I I a --- 7nn 

SENSOR DATA UNIT A 

;=====~,;~==========;========I:====----a 

: CHAN : Amp1 <pT> : P CDEG) : SNR I 

:======:;===========:=========:=====---a 

I 

1 X : 0.4900 EO : 179 : 19 I 

*,----.--;-----------;---------;--------I 

a Y : 0.8861 EO : -7 : 15 I 1 

I -- 8 8 I 

a Z : 0.1060 El 169 : 17 I 

:------;-----------;---------:--------* 

: REF SNRS T PM SNRS T $ 

; ====; : I -- a I -- 1 ; === ; I 1 ---- I I -- I I -- I I --- I I I 

:X: : 16 : 4898 : 52 27 : 1 15 : I 

I I :---:--:--:--:---:--:----n--m--m--m---: I I 

SENSOR DATA UNIT B I------I----------- --------- ----

: CHAN : Amp1 <pT> : P <DEG) : SNR a 

.................

a X : 0.6247 EO : 179 : 20 a 1 

------;-----------;---------;--------I 

I Y : 0.2005 EO : -167 : 11 1 

8 S 8 . 8 

I Z : 0.1937El : 48 : 44 I 

; ------ ' -----------:---------;--------a 

: REF SNRS T PM SNRS T : 

: --,=a : I -- a I -- I ; === ; I I ---- I I -- I I -- a I ---

I I 

:Z: : 27 : : 4946 : : 0 1 : 41 : : 15 : I I I I I a I I I I I m---~--*--'--.---@--.----'--'--~--~---: - 

SENSOR DATA UNIT C 

;------a-----------I-------,-I----,,--. I-------.---- I---------#--------I 

: CHAN : Amp1 <pT> : P <DEG) : SNR I 

....................................... 

I I a X : 0.4455 EO : -178 : 17 

8 . . m 

: REF SNRS T PM SNRS T : 

=== ; I I -- I I : === : : ==I= : I -- I I -- I a --- I I I 

:Z: : 26 : : 4980 : : -10 : 37 : : 15 : I 

I I I I I I a I I I I I 

I---l--m--I--m---a--*----m--*--n--'---m 
I -,--------- I I I I --,,

---- 

TIME <HH:MM) : 12:23 I PROJECT 1 ~04 I 

I I a 

------ a a --,,: 

EXPECTED EXPECTED EXPECTED 

CURRENT TIMES ARE44 EGTU44LS MOMENT 

;-------; \ / ;=======: I ---,

I --- I ------- I 

: 1 -:- : I 

300 --- a 

I 

I ------- : I :-------: -,,-: 

<AMPS > CSQ-METERS) <FIMPxMxM> 

SENSOR DeTR UNIT A :------;-----------;---------l--------I I--------* 

: CHAN : Amp1 <pT> : P <DEG) : SNR I 

1 1------1-----------:---------:--------8 ------ I----------- l 

a X : .4897 EO : 167 : 19 I 

;------;-----------;---------;--------I 

• . 8 • I 

: REF SNRS T PM SNRS T: 

: ==3 : I -- I I -- I I -,- I I --- I ; I=== : I ,- a I -- I ; === ; 

SENSOR DATe UNIT B ;------I----------- I-----------:--------- -,------#--------I I--------I 

: CHAN : Amp1 <pT) : P <DEG> : SNR • 

....................................... 

I x : .6230 EO -176 : 20 8 I 

:------:-----------:---------:--------I 

, Y : .ZOO5 EO : -154 : 11 I 

I 

. 8 1- I - 

I Z : .I935 El : 80 : 43 a 

I 

:------:-----------;---------;--------a 

: REF SNRS T PM SNRS T: I --- I I I I -- I I -- I I --- I I I I ---- I 1 1 I -- I I -- I I --- I I a 

SENSOR DATFI UNIT C I 

, --- ,-,-,--,--- ,,-,-,- -------I -:-----------:---------:--------a 

: CHAN Amp1 <pT) : P <DEG> : SNR I 

I--,---l--,----,,--I,,------- --------I 

I X : ,4446 EO : -177 : 17 I 

;------:-----------;---------:--------: 

: REF SNRS T PM SNRS T : 

: === : I -- I I -- I I --- I I I. ; I==--, ; I -- a I -- I I --- I I I 
REFERENCES 

1. Sacks, H. Kenneth, "Trapped Miner Location and Communication Systems," 

Underground Mine Communications (Part 4), Bureau of Mines Information 

Circular #8745, U.S. Uepartment of the Interior, 1977, pp. 31-43. 

2. Durkin, John, "Performance Evaluation of Electromagnetic Techniques for 

the Location of Trapped Miners," Bureau of Mines Report of Investi gat i ons 

#8711, U.S. Department of the Interior, 1982. 

3. Rorden, L .H., et . a1 . , "Phase 1 - Development of System Concept for 

Location of Trapped Miners in Deep Mines by an Electromagnetic Method," 

Phase 1 Report, U.S. Department of the Interior Bureau of Mines Contract 

50199009, Develco, Inc., October 1979. 

4. Rorden, L.H., et. a1 ., "Methods and Apparatus Employing an Alternating 

Magnetic Field for Determining Location," (Patent applied for). 

5. Morrison, H.F., et . a1 . , "Experience with the EM-60 Electromagnetic 

System for Geothermal Exploration in Nevada," Geophysics, Vol. 48, No. 8 

(August 1983), p. 1093. 

6. Moore, T.C., et. a1 ., "Borehole Location System Concept Demonstration 

Tests," Final Report (1132-780505), U.S. Department of the Interior Bureau 

of Mines Contract 50177074, Develco, Inc., May 1978. 

7. Simmons, C.H., "Uevelopment and Prototype Production of a Trapped Miner 

Signal 1 i ng TransmitterITranscei ver ," U.S. Department of the Interior 

gureau of Mines Contract 303950017, NTIS #PB82-24426U, June 1981. 

8 Iufer, E.J., "20 Ft. Helmholtz Coi 1 Cali bration Report ," Contract No. 

LA28H9450F, E.J. Iufer & Associates Inc., Los Altos, CA, January 5, 1984. 

9. Raab, F.H., "Adapti ve-Noise-Cancel lation Techniques for 

Through-the-Earth Electromagnetics, Volume 111," U.S. Department of the 

Interior, Bureau of Mines Contract J0318070, Green Mountain Radio Research 

Company, February 1984. 5 

- 

10. Evans, J.E., et . a1 . , "Design of a Sanguine Noise Processor Based Upon 

Worldwide Extremely Low Frequency (ELF) Recordings," IEEE Transactions on 

Communications, Vol. Com-22, No. 4, pp. 528-539, April 1974. 

11. Maxwell, E. and Stone, D., "Natural Fields from 1 cps to 100 kc," IEEE 

Tran'sactions on Antennas and Propagation, Vol. AP11, No. 3, pp. 339-343, 

May 1963.