"@(#)dsdata.txt	1.12 - 2003/09/11 15:12:57"
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*                        dsdata.txt                                  *
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OVERVIEW:

Information about survey monuments on record with the National Geodetic
Survey (NGS) is published in a Digital Survey DATA (DSDATA) format.
The format consists of fixed field records in an 80 column ASCII text file.
The authoritative source for digital survey data format is the NGS bluebook.
This document is an extract of the bluebook for public convenience.

An individual DSDATA record of a monument is called a datasheet.  Datasheets
are sorted alphanumerically by station designation within a DSDATA file. 

The last line of a correctly retrieved DSDATA file is:
***retrieval complete.

The first line of each datasheet is:
1        NATIONAL GEODETIC SURVEY,   Retrieval Date =
followed by the date the data was extracted from the NGS database.

The second line of each datasheet begins with the PID in column 2,
then is followed by a row of asterisks that begins in column 9.

Most other data items are identified by the data identifier text in cc 10-22.
Data identifier text text is characterised by a hyphen(-) in column 22.

The following data items are exceptions that require the use of cc 10-22,
and are identified by the following codes, all which start in column 8.
Note that projection data items are identified by codes in cc 8-11:

  Identifier     Data Item
       
      *          Current Survey Control

      .          Data Determination Text

      ;SPC       SPC Coordinate Data

      ;UTM       UTM Coordinate Data
      
      !SPC       SPC Combined Factor Data

      !UTM       UTM Combined Factor Data

      :          Primary Azimuth Object

      |          Box Score (Reference Objects)

      _          Mark Setting Information

      +          Mark Setting Information Continued












SUMMARY OF DATA ITEMS:

                                ***
 DATA ITEM: Special Control Station Header
 DISPLAYED: Only when station is one of those types listed under EXAMPLES.
 COMMENTS :
 EXAMPLES :________________________________________________________________
 AA3495  CORS        -  This is a GPS Continuously Operating Reference Station.
 HV8128  FBN         -  This is a Federal Base Network Control Station.
 HV9260  CBN         -  This is a Cooperative Base Network Control Station.
 RF0849  PACS        -  This is a Primary Airport Control Station.
 RF0850  SACS        -  This is a Secondary Airport Control Station.
 CJ0500  TIDAL BM    -  This is a Tidal Bench Mark

                                ***
 DATA ITEM: Designation
 DISPLAYED: Always
 COMMENTS : Usually the DESIGNATION does not match exactly with the STAMPING.
 EXAMPLES :________________________________________________________________
 AA3495  DESIGNATION -  GAITHERSBURG CORS L1 PHASE CENTER
 RF0849  DESIGNATION -  CARIPORT
 CA0570  DESIGNATION -  MP 77-5015
 AA8531  DESIGNATION -  66-26

                                ***
 DATA ITEM: CORS Identifier
 DISPLAYED: When Station is a Continuously Operational Reference Station
 COMMENTS :
 EXAMPLES :________________________________________________________________
 AW5607  CORS_ID     -  HOUS
 ER0702  CORS_ID     -  PIE1
 AA3495  CORS_ID     -  GAIT

                                ***
 DATA ITEM: Station Permanent Identifier (PID)
 DISPLAYED: Always
 COMMENTS : The PID is also found on the left side of each datasheet record.
            The PID is always 2 upper case letters followed by 4 numbers.
 EXAMPLES :________________________________________________________________
 AA3495  PID         -  AA3495
 RF0849  PID         -  RF0849
 TV0007  PID         -  TV0007

                                ***
 DATA ITEM: STATE/COUNTY
 DISPLAYED: Always, but County may be blank.
 COMMENTS : Bououghs may be used for Alaska; Parishes are used for Louisiana
 EXAMPLES :________________________________________________________________
 FV1057  STATE/COUNTY-  CA/SAN LUIS OBISPO
 BW0029  STATE/COUNTY-  LA/POINTE COUPEE
 TT0026  STATE/COUNTY-  AK/
 TT4608  STATE/COUNTY-  AK/MATANUSKA-SUSITNA

                                ***
 DATA ITEM: USGS Quad
 DISPLAYED: Always, but may be blank
 COMMENTS : This is the name of the USGS 7.5 minute series map sheet which
            shows the area of the station.  The station may or may not appear
            as a map feature.  NGS sometimes publishes data according to the
            USGS quadrangle (quad) system, for which the USGS quad sheet
            name is used as a reference.
 EXAMPLES :________________________________________________________________
 AA3495  USGS QUAD   -  GAITHERSBURG (1986)
 FA3038  USGS QUAD   -  ELLENDALE (1973)
 TV1290  USGS QUAD   -  
 FV1057  USGS QUAD   -  CYPRESS MOUNTAIN (1979)

                                ***
 DATA ITEM: Current Survey Control
 DISPLAYED: Always, but the HEIGHT may be blank if the station
            is a horizontal control station only.
 COMMENTS : Current Survey Control is identified by a '*' in cc8
            and comes under the heading "*CURRENT SURVEY CONTROL"

            The horizontal datum in use is the North American Datum of 1983
            (NAD 83).  This datum also defines ellipsoid vertical height.
            The orthometric vertical datum in use is the North American
            Vertical Datum of 1988 (NAVD 88).

            NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums.
            Care should be taken not to "mix" current datum(s) with
            past datum(s) within a project. 

            NAD83 (1986) indicates positions on the NAD83 datum for the
            North American Adjustment, completed in 1986.
            NAD83 (nnnn) indicates positions on the NAD83 datum for the
            North American Adjustment, but readjusted to a State High
            Accuracy Reference Network (HARN) on the date shown in (nnnn).
            NAD83 (CORS) indicates positions which are part of the CORS
            network.

            There are various Horizontal Control sources, as specified below:

            ADJUSTED = Least squares adjustment.
                       (Rounded to 5 decimal places.)

            HD_HELD1 = Differentially corrected hand held GPS observations.
                       (Rounded to 2 decimal places.)

            HD_HELD2 = Autonomous hand held GPS observations.
                       (Rounded to 1 decimal places.)

            SCALED   = Scaled from a topographic map.
                       (Rounded to 0 decimal places.)


            NAVD 88 orthometric heights are displayed where available.
            If there was a height for the station on the National Geodetic
            Vertical Datum of 1929 (NGVD 29), then that height will be
            displayed under SUPERSEDED SURVEY CONTROL.

            There are various Vertical Control sources, as specified below:

            ADJUSTED = Direct Digital Output from Least Squares Adjustment
                       of Precise Leveling.
                       (Rounded to 3 decimal places.)

            ADJ UNCH = Manually Entered (and NOT verified) Output of
                       Least Squares Adjustment of Precise Leveling.
                       (Rounded to 3 decimal places.)

            POSTED   = Pre-1991 Precise Leveling Adjusted to 
                       the NAVD 88 Network After Completion of
                       the NAVD 88 General Adjustment of 1991.
                       (Rounded to 3 decimal places.)

            READJUST = Precise Leveling Readjusted as Required
                       by Crustal Motion or Other Cause.
                       (Rounded to 2 decimal places.)

            N HEIGHT = Computed from Precise Leveling Connected
                       at Only One Published Bench Mark.
                       (Rounded to 2 decimal places.)

            RESET    = Reset Computation of Precise Leveling.
                       (Rounded to 2 decimal places.)

            COMPUTED = Computed from Precise Leveling Using
                       Non-rigorous Adjustment Technique.
                         (Rounded to 2 decimal places.)

            LEVELING = Precise Leveling Performed by Horizontal
                       Field Party.
                        (Rounded to 2 decimal places.)

            H LEVEL  = Level between control points not connected
                       to bench mark.
                        (Rounded to 1 decimal places.)

            GPS OBS  = Computed from GPS Observations.
                       (Rounded to 1 decimal places.)

            VERT ANG = Computed from Vertical Angle Observations.
                       (Rounded to 1 decimal place;
                        If No Check, to 0 decimal places.)

            SCALED   = Scaled from a Topographic Map.
                       (Rounded to 0 decimal places.)

            U HEIGHT = Unvalidated height from precise leveling
                       connected at only one NSRS point.
                       (Rounded to 2 decimal places.)

            VERTCON  = The NAVD 88 height was computed by applying the
                       VERTCON shift value to the NGVD 29 height. 
                       (Rounded to 0 decimal places.)


            NOTE:    NAVD 88 and NGVD 29 heights in meters are
                     converted to U.S. Survey Feet by using the
                     conversion factor:
                       U.S. Survey Feet = (39.37 / 12.00) x meters
                     Height in feet is rounded to 1 less decimal
                     place than the corresponding height in meters.


 EXAMPLES :________________________________________________________________
 AA0000                         *CURRENT SURVEY CONTROL
 AA0000 
__________________________________________________________________
 AA3495* NAD 83(CORS)-  39 08 02.34060(N)    077 13 15.51927(W)     ADJUSTED  
 RF0849* NAD 83(1992)-  46 52 08.05211(N)    068 00 53.02360(W)     ADJUSTED  
 TA0047* NAD 83(1986)-  48 04 54.20   (N)    090 45 48.42   (W)     HD_HELD1  
 AC3384* NAD 83(1986)-  25 57 14.7    (N)    081 43 29.2    (W)     HD_HELD2  
 HV0454* NAD 83(1986)-  38 20 52.     (N)    076 13 38.     (W)     SCALED    
 DX3756* NAVD 88     -       462.113  (meters)    1516.12   (feet)  ADJUSTED
 FQ0856* NAVD 88     -      2012.200  (meters)    6601.69   (feet)  POSTED    
 DB0356* NAVD 88     -       -11.886  (meters)     -39.00   (feet)  READJUSTED
 DC2131* NAVD 88     -      1096.93   (meters)    3598.8    (feet)  N HEIGHT  
 AI5086* NAVD 88     -       123.68   (meters)     405.8    (feet)  U HEIGHT
 GP0162* NAVD 88     -      1456.97   (meters)    4780.1    (feet)  RESET     
 DE3069* NAVD 88     -        38.28   (meters)     125.6    (feet)  LEVELING  
 GP0641* NAVD 88     -      1831.8    (meters)    6010.     (feet)   GPS OBS   
 BW0768* NAVD 88     -        59.70   (+/-2cm)     195.9    (feet)  VERTCON   
 BW2469* NAVD 88     -       125.     (meters)     410.     (feet)  SCALED    
 FG1799* NAVD 88     -                                                        
 TV0377* LOCAL TIDAL -         7.2    (meters)      24.     (feet)  VERT ANG


                                ***
 DATA ITEM: Datum Tag
 DISPLAYED: Displayed for horizontal NAD 83 Latitude,Longitudes only.
 COMMENTS : Shown in parentheses immediately following NAD 83.

            NAD 83 (1986) indicates positions on the NAD83 datum for the
            North American Adjustment, completed in 1986.

            NAD 83 (nnnn) indicates positions on the NAD83 datum for the
            North American Adjustment, but readjusted to a State High
            Accuracy Reference Network (HARN) on the date shown in (nnnn).
            NAD 83 (CORS) indicates positions which are part of the CORS

            NAD 83 (CORS) is an obsolete Tag which has been replaced
            by (CORS96), (PACP00), (MARP00)

            NAD 83 (CORS96) indicates a CORS position referenced to
            the North American tectonic plate.

            NAD 83 (PACP00) indicates a CORS position referenced to
            the Pacific tectonic plate.

            NAD 83 (MARP00) indicates a CORS position referenced to
            the Mariana tectonic plate.
 EXAMPLES :________________________________________________________________
 HV0454* NAD 83(1986)   38 20 52.     (N)    076 13 39.     (W)     SCALED    
 AI6225* NAD 83(1997)   43 11 35.60539(N)    088 13 52.98928(W)     ADJUSTED  
 AB6382* NAD 83(CORS96) 31 52 26.11241(N)    102 18 54.55652(W)     ADJUSTED  
 AJ8466* NAD 83(PACP00) 19 43 09.03079(N)    155 03 09.62007(W)     ADJUSTED  
 AF9627* NAD 83(MARP00) 13 35 21.55629(N)    215 07 53.87321(W)     ADJUSTED  

                                ***
 DATA ITEM: Epoch Date
 DISPLAYED: When Horizontal Position Requires
 COMMENTS : The epoch date is used for stations in regions of episodic and/or
            continuous horizontal crustal motion where the position changes
            in time.  The epoch date indicates the time the published
            horizontal coordinates are valid.

            All stations with an adjusted horizontal position that falls within
            a designated crustal motion region will have an epoch date displayed
            on the datasheet.  Stations outside of these regions will not have
            an epoch date.  As the crustal motion effect tapers to zero before
            reaching a region's boundary, stations immediately inside that
            boundary and having an epoch date will normally have consistant
            positions with stations outside that boundary with no epoch date.

            To aid users with changing coordinates through epochs, NGS has
            developed software package HTDP to model changes in California
            and parts of Alaska.  HTDP is available from the NGS Information
            Services Branch.
 EXAMPLES :________________________________________________________________
 AA3495  EPOCH DATE  -        1996.00
 EV3471  EPOCH DATE  -        1991.35

                                ***
 DATA ITEM: X, Y, Z 
 DISPLAYED: When adjusted Horizontal Position and Ellipsoid Height are available.
 COMMENTS : These values represent earth-centered earth-fixed coordinates,
            where the X axis follows zero degrees longitude, the Z axis follows
            positive 90 degrees latitude and the Y axis completes a right hand
            system.
 EXAMPLES :________________________________________________________________
 AA3495  X           -   1,095,790.787 (meters)                     COMP
 AA3495  Y           -  -4,831,328.133 (meters)                     COMP
 AA3495  Z           -   4,003,934.481 (meters)                     COMP

                                ***
 DATA ITEM: Laplace Correction
 DISPLAYED: For adjusted positions in area covered by the 'DEFLEC' Software.
 COMMENTS : The Laplace correction is the quantity which, when added to an
            astronomic azimuth, yields a geodetic azimuth.

            The simplified Laplace equation, which assumes horizontal lines
            of sight (cotangent of zenith angle ~ zero) and which assumes a
            clockwise reference frame during model development is:

            LAPLACE CORR = (a - A)
                         = (eta) * tan(geodetic latitude)
            where:
            a    =  Geodetic azimuth
            A    =  Astronomic azimuth
            eta  =  Deflection of the vertical in the prime-vertical plane,
                    an east-west component.

            The reader is cautioned that the Laplace equation has also been
            derived by others using a counterclockwise reference frame,
            which leads to subtracting the Laplace correction from the
            astronomic azimuth to yield a geodetic azimuth:
                  Laplace corr = (A - a).
            However, NGS uses a clockwise reference frame.
 EXAMPLES :________________________________________________________________
 RF0849  LAPLACE CORR-           3.39  (seconds)                    DEFLECT
 EV3471  LAPLACE CORR-           0.79  (seconds)                    DEFLECT
 TV1290  LAPLACE CORR-          -0.02  (seconds)                    DEFLECT
 EZ4149  LAPLACE CORR-          -3.44  (seconds)                    DEFLECT

                                ***
 DATA ITEM: Ellipsoid Height
 DISPLAYED: When available
 COMMENTS : The ellipsoid height is the elevation of the station above the 
            reference ellipsoid for horizontal datum, currently the NAD83
            ellipsoid.  The ellipsoid is a reference surface for how the
            world appears, with respect to physical location.
            As a very close approximation:

                     h = H + N
            where
               h  =  ellipsoid height
               H  =  orthometric height
               N  =  geoid height

            In theory this equation is not exact because the ellipsoid height
            is normal to the ellipsoid, orthometric height is normal to the
            geoid, and these two surfaces are not necessarily parallel.
            In practice these three data item quantities will not usually
            satisfy the above equation since they were derived from seperate
            sources.  The above equation assumes a model where the geoid
            is above the ellipsoid, and terrain above the geoid.
            The date (mm/dd/yy) attached to the ellipsoid height is the date
            when the ellipsoid height was adjusted.  If the day is unknown
            then it is filled with "??".
 EXAMPLES :________________________________________________________________
 AA3495  ELLIP HEIGHT-         109.047 (meters)           (03/??/02) GPS OBS
 HV8128  ELLIP HEIGHT-         -24.700 (meters)           (02/12/02) GPS OBS
 FT1606  ELLIP HEIGHT-         974.023 (meters)           (03/??/02) GPS OBS

                                ***
 DATA ITEM: Geoid Height
 DISPLAYED: For areas covered by the 'GEOID' software.
 COMMENTS : The geoid height is the elevation of the geoid above the horizontal
            datum's reference ellipsoid.  The geoid is a specific equi-
            geopotential surface (geop), that best fits global mean sea level.
            The geoid is a reference surface for how the world acts,
            with respect to the geopotential force of gravity.
            The majority of the conterminous United States shows a negative
            geoid height, indicating that the geoid is below the ellipsoid.
 EXAMPLES :________________________________________________________________
 RF0849  GEOID HEIGHT-         -23.39  (meters)                     GEOID96
 TU0165  GEOID HEIGHT-         -28.00  (meters)                     GEOID96
 TV0007  GEOID HEIGHT-         -40.70  (meters)                     GEOID96

                                ***

 DATA ITEM: Dynamic Height
 DISPLAYED: For stations with an NAVD88 height and Modeled Gravity.
 COMMENTS : The dynamic height of a benchmark is the height at
            a reference latitude of the geopotential surface through the
            benchmark.  This value is of interest because two stations with
            different orthometric heights may have similar geopotential,
            due to undulations of the geopotential reference surface (geoid).
            The source of a dynamic height is always computed.
            The reference latitude for the United States is North 45 degrees.

            Dynamic heights were computed from geopotential heights
            (geopotential numbers) which were obtained for all bench marks
            in the general adjustment of the North American Vertical
            Datum of 1988 (NAVD88).  A dynamic height referenced to the
            International Great Lakes Datum of 1985 is then obtained by
            dividing the adjusted NAVD88 geopotential height of a 
            bench mark by the normal gravity value (G) computed on the
            Geodetic Reference System of 1980 (GRS 80) ellipsoid
            at 45 degrees latitude (G = 980.6199 gal). 

            A related unit for measuring geopotential is the geopotential
            number (C), which was adopted by the IAG in 1955.  
            The geopotential number equals the dynamic height multiplied by
            the normal gravity at the reference latitude:
                          C = H(dynamic) * gamma(ref).
            The geopotential number (C) is measured in geopotential units
            (g.p.u.), where:
                  1 g.p.u. = 1 kgal meter = 1000 gal meter.

            Since local gravity near sea level is approximately 0.98 kgal,
            the magnitude of geopotential numbers (C) are approximately
            that of orthometric height in meters, which leads to better
            intuitive understanding.
 EXAMPLES :________________________________________________________________
 DB0356  DYNAMIC HT  -         -11.870 (meters)    -38.94   (feet)  COMP
 HV0454  DYNAMIC HT  -           1.026 (meters)      3.37   (feet)  COMP
 DC0409  DYNAMIC HT  -        1055.66  (meters)   3463.4    (feet)  COMP

                                ***
 DATA ITEM: Modeled Gravity
 DISPLAYED: When available.
 COMMENTS : The interpolated gravity value which was used in the NAVD 88
            general adjustment.
 EXAMPLES :________________________________________________________________
 HV8128  MODELED GRAV-     980,028.4   (mgal)                       NAVD 88
 EV3471  MODELED GRAV-     979,412.1   (mgal)                       NAVD 88
 CA0570  MODELED GRAV-     979,272.6   (mgal)                       NAVD 88

                                ***
 DATA ITEM: Survey Control Order and Class
 DISPLAYED: For Adjusted Control Only
 COMMENTS : The Order will be 'HORZ ORDER', 'VERT ORDER' or 'ELLIP ORDER'
            depending on whether it refers to Horizontal control,
            Vertical Orthometric control or Vertical Ellipsoid control.

            ORDER AND CLASS: HORIZONTAL
            ***************************
            Horizontal station order and class for first-, second-, and
            third-order stations are defined in the Federal Geodetic Control
            Committee publication "Standards and Specifications for Geodetic
            Control Networks".  In addition:

            Horizontal A-order stations have a relative accuracy of
            5 mm +/- 1:10,000,000 relative to other A-order stations.

            Horizontal B-order stations have a relative accuracy of
            8 mm +/- 1: 1,000,000 relative to other A- and B-order stations.

            Most concurrently published NAD 83 positions have consistent
            coordinate accuracy, regardless of the date appended to the datum.
            This means the relative accuracy of most stations will continue to
            meet their published standard (A- and B-order, as well as first-,
            second- and third-orders) even when the datum tags are different.

            There is one important exception to the last paragraph.  High
            accuracy stations (A- and B-order) are routinely published prior
            to the readjustment of the remaining horizontal control stations
            in the region.  These remaining stations that do not have a 
            corresponding adjustment date suffix will may not have consistent
            horizontal coordinate values with the A- and B-order stations in
            that region until the regional adjustment has been completed.
            Until that time, the high accuracy stations in that region are
            flagged as special-status positions.  The following text
            applies to them:

     SPECIAL STATUS - The horizontal position of this high accuracy station is
     hereby published prior to the readjustment of the remaining lower-order
     (first-, second-, and third-order) stations in the region.  The lower-
     order non-suffixed stations in this region will not have consistant
     horizontal coordinate values with this station until the regional
     readjustment has been completed.


            ORDER AND CLASS: ORTHOMETRIC VERTICAL
            *************************************
            Vertical station order and class for first-, second-, and
            third-order stations are defined in the Federal Geodetic Control
            Committee publication "Standards and Specifications for Geodetic
            Control Networks".  In addition:

            Normal bench marks with unknown order will display a '?'.
            Vertical control which were determined only for the purpose of
            supplying a height for Horizontal Distance Reductions are
            assigned an order of 'THIRD'.  If these types of heights do
            not have supporting observations then the Order is displayed
            as 'THIRD ?'.  

            Class 0 is used for special cases of
            orthometric vertical control as follows:

               Vertical Order/Class               Tolerance Factor
               --------------------               ----------------
                FIRST    CLASS 0                   2.0 mm or less
                SECOND   CLASS 0                   8.4 mm or less
                THIRD    CLASS 0                  12.0 mm or less

            "Posted bench marks" are vertical control points in the NGS data 
            base which were excluded from the NAVD 88 general adjustment.
            Some of the bench marks were excluded due to large adjustment
            residuals, possibly caused by vertical movement of the bench marks
            during the time interval between different leveling epochs.
            Adjusted NAVD 88 are computed for posted bench marks by
            supplemental adjustments.

            A range of mean distribution rate corrections is listed for each
            posted bench mark in the data portion of the publication.
            A summary table of the mean distribution rates and their codes is
            listed below.  The mean distribution rate corrections which were
            applied to the original leveling observations is a good
            indication of the usefulness of the posted bench marks' adjusted
            NAVD 88 heights.

                 Distribution                     Distribution
                  Rate Code                      Rate Correction
                 ------------                    ---------------
                    "a"                        0.0 thru 1.0 mm/km
                    "b"                        1.1 thru 2.0   "
                    "c"                        2.1 thru 3.0   "
                    "d"                        3.1 thru 4.0   "
                    "e"                        4.1 thru 8.0   "
                    "f"                        greater than 8.0 mm/km

            POSTED BENCH MARKS SHOULD BE USED WITH CAUTION.  As is the case for
            all leveling projects, the manditory FGCS check leveling two-mark or
            three-mark tie procedure will usually detect any isolated movement
            (or other problem) at an individual bench mark.  Of course, regional
            movement affecting all the marks equally is not detected by the two-
            or three-mark tie procedure.


            ORDER AND CLASS: ELLIPSOID VERTICAL
            ***********************************
            The following ellipsoid height order and class relative accuracy.

                Ellipsoid Height                    Maximum Height
                 Classification                   Difference Accuracy
               ------------------                 -------------------
               FIRST      CLASS 1                  0.5 (mm)/sqrt(km)
               FIRST      CLASS 2                  0.7
               SECOND     CLASS 1                  1.0
               SECOND     CLASS 2                  1.3
               THIRD      CLASS 1                  2.0
               THIRD      CLASS 2                  3.0
               FOURTH     CLASS 1                  6.0
               FOURTH     CLASS 2                 15.0
               FIFTH      CLASS 1                 30.0
               FIFTH      CLASS 2                 60.0

           The ellipsoid height difference accuracy (b) is computed from a
           a minimally constrained correctly weighted least squares adjustment
           by:
                b = s / sqrt(d)

           where
                b = height difference accuracy 
                s = propagated standard deviation of ellipsoid height
                    difference in millimeters between control points
                    obtained from the least squares adjustment.
                d = horizontal distance between control points in kilometers

 EXAMPLES :________________________________________________________________
 AA3495  HORZ ORDER  -  SPECIAL (CORS)
 HV8128  HORZ ORDER  -  A
 HV9260  HORZ ORDER  -  B
 AA0169  HORZ ORDER  -  FIRST
 FG1796  HORZ ORDER  -  SECOND
 FG1797  HORZ ORDER  -  THIRD

 HV8128  VERT ORDER  -  FIRST     CLASS II
 HU0680  VERT ORDER  -  SECOND    CLASS 0
 FG0846  VERT ORDER  -  THIRD (See Below)
 GP0162  VERT ORDER  -  THIRD
 HH0701  VERT ORDER  -  THIRD     CLASS 0
 LX7164  VERT ORDER  -  THIRD ?
 FG0744  VERT ORDER  -  ? 
 FQ0849  VERT ORDER  -  * POSTED, Code a , SEE BELOW
 GP0241  VERT ORDER  -  * POSTED, Code b , SEE BELOW
 FR0070  VERT ORDER  -  * POSTED, Code c , SEE BELOW
 TF1074  VERT ORDER  -  * POSTED, Code d , SEE BELOW
 TF1144  VERT ORDER  -  * POSTED, Code e , SEE BELOW
 TF0916  VERT ORDER  -  * POSTED, Code f , SEE BELOW
 FR0371  VERT ORDER  -  * POSTED, Code NC , SEE BELOW
 EV3471  VERT ORDER  -  * READJUSTED, Code A , SEE BELOW
 AA3495  ELLP ORDER  -  SPECIAL (CORS)

 TV1290  ELLP ORDER  -  FIRST     CLASS II
 RF0849  ELLP ORDER  -  THIRD     CLASS I
 HV8128  ELLP ORDER  -  FOURTH    CLASS I

                                ***
 DATA ITEM: Text regarding Horizontal Control
 DISPLAYED: As required when explaining source of data values.
 COMMENTS :  
 EXAMPLES :________________________________________________________________
AA0000.The horizontal coordinates were established by classical geodetic methods
AA0000.and adjusted by the National Geodetic Survey in June, 1995.

AA0000.The horizontal coordinates were established by classical geodetic methods
AA0000.and adjusted by the National Geodetic Survey.

AA0000.The horizontal coordinates were established by GPS observations
AA0000.and adjusted by the National Geodetic Survey in June, 1995.

AA0000.The horizontal coordinates were established by GPS observations
AA0000.and adjusted by the National Geodetic Survey.

AA0000.The horizontal coordinates were established by VLBI observations
AA0000.and local terrestrial surveys and adjusted by the National Geodetic
AA0000.Survey in June, 1995.

AA0000.The horizontal coordinates were established by VLBI observations
AA0000.and local terrestrial surveys and adjusted by the National Geodetic
AA0000.Survey.

AA0000.The horizontal coordinates were scaled from a topographic map and have 
AA0000.an estimated accuracy of +/- 6 seconds.

AA0000.No horizontal observational check was made to the station.

AA0000.This is a SPECIAL STATUS position.  See SPECIAL STATUS under the 
AA0000.DATUM ITEM on the data sheet items page.

AA0000.The horizontal coordinates are valid at the epoch date displayed above.
AA0000.The epoch date for horizontal control is a decimal equivalence
AA0000.of Year/Month/Day.

                                ***
 DATA ITEM: Text regarding Vertical Control
 DISPLAYED: As required when explaining source of data values.
 COMMENTS : 
 EXAMPLES :________________________________________________________________
AA0000.The orthometric height was determined by differential leveling 
AA0000.and adjusted by the National Geodetic Survey in June, 1990.

AA0000.The orthometric height was determined by differential leveling
AA0000.and adjusted by the National Geodetic Survey.

AA0000.The orthometric height was computed from unverified reset data.

AA0000.The orthometric height was key entered from printed documents
AA0000.and not key verified.

AA0000.The approximate orthometric height was determined by applying 
AA0000.unadjusted height differences to other nearby adjusted values.

AA0000.The orthometric height was determined by differential leveling.
AA0000.The vertical network tie was performed by a horz. field party for horz. 
AA0000.obs reductions. Reset procedures were used to establish the elevation.

AA0000.The orthometric height was determined by vertical angle observations.

AA0000.The orthometric height was determined by GPS observations.

AA0000.The orthometric height was scaled from a topographic map.
AA0000.The NAVD 88 height was computed by applying the VERTCON shift value to
AA0000.the NGVD 29 height (displayed under SUPERSEDED SURVEY CONTROL.)

AA0000.No vertical observational check was made to the station.

AA0000.* This is a POSTED BENCH MARK height.  Code A indicates a distribution
AA0000.rate of 0.0 thru 1.0 mm/km.

AA0000.* This is a READJUSTED BENCH MARK height.  Code NC indicates the bench 
AA0000.mark was located on a no-check spur therefore a value was not computed.

AA0000.The height was derived from older observations constrained to new
AA0000.heights in a crustal motion area.  The height is approximate in 
AA0000.relation to other heights in its vicinity.

AA0000.The height was determined by precise leveling from only one NGRS
AA0000.bench mark.  This was not adequate "tie leveling" to NGRS and was
AA0000.allowed ONLY to validate the GPS-derived height.

AA0000.WARNING-GPS observations at this control monument resulted in a GPS 
AA0000.derived orthometric height which differed from the leveled height by
AA0000.more than one decimeter (0.1 meter).

AA0000.WARNING-Repeat measurements at this control monument indicate possible
AA0000.vertical movement.

CJ0500.This mark is designated as VM 4064 in the Oceanographic Products
CJ0500.and Services Division Tidal Bench Mark database.
       NOTE: If a web browser is used to retrieve an NGS bench mark that is
       also a tidal bench mark, the words "Oceanographic Products" will be
       highlighted and will provide a link to the series of descriptions and
       tide height references in the Oceanographic Products and Services
       Division (OPSD) Tidal Bench Mark database that includes the bench mark.
       The specific bench mark is uniquely identified by a corresponding
       tide station number and state, which are provided at an intermediate
       web page, where a link to the OPSD Home Page is also available
       for further tidal bench mark information.

                                ***
 DATA ITEM: Text regarding Other Data Control
 DISPLAYED: As required when explaining source of data values.
 COMMENTS : 
 EXAMPLES :________________________________________________________________
 AA0000.The XYZ, and position/ellipsoidal ht. are equivalent.
 AA0000.The X, Y, and Z were computed from the position and the ellipsoidal ht.
 AA0000.The Laplace correction was computed from DEFLEC93 derived deflections.
 AA0000.The ellipsoidal height was determined by GPS observations
 AA0000.and is referenced to NAD 83.
 AA0000.The geoid height was determined by GEOID93.
 AA0000.The dynamic height is computed by dividing the NAVD 88
 AA0000.geopotential number by the normal gravity value computed on the
 AA0000.Geodetic Reference System of 1980 (GRS 80) ellipsoid at 45
 AA0000.degrees latitude (G = 980.6199 gals).
 AA0000.The modeled gravity was interpolated from observed gravity values.
 AA3495.No superseded survey control is available for this station.
 AA0000.NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums.
 AA0000.See file format.dat to determine how the superseded data were derived.
 AA0170.The vertical order pertains to the superseded datum.

                                ***
 DATA ITEM: Grid Coordinate Systems:
            State Plane Coordinate System of 1983 (SPC)
            Universal Transverse Mercator (UTM)
 DISPLAYED: SPC coordinates are shown where zones where available.
            UTM zones are available worldwide, but coordinates are shown only
            for those stations with horizontal control.
 COMMENTS : UTM units are always in meters(MT).  In addition to meters,
            SPC units may also be expressed in U.S. Survey Foot(sFT), or
            International Foot(iFT), where:

            U.S. Survey Foot   :=  39.37 inches = 1 meter, exactly
            International Foot :=        1 inch = 2.54 centimeters, exactly

            All azimuths are referenced clockwise from north.
            Stations near zone limits may report positions for each zone.
            Scale Factor multiplied by ellipsoid distance equals grid distance.
            Convergence is also known as the mapping angle.
            Convergence plus grid azimuth yields geodetic azimuth.
            The second-term correction known as the Arc-to-Chord correction
            has not been included in the convergence.

            Scaled SPC values that are provided for stations which do not
            have adjusted horizontal control have no digits to the right
            of the decimal.  Scaled SPC do not report a Scale Factor or
            Convergence, but report an Estimated Accuracy.

            A Grid Coordinate record contains:
             Zone, Northing, Easting, Units, Scale Factor, Convergence(d mm ss.s)
 EXAMPLES :________________________________________________________________
 RF0849;                    North         East     Units Scale Factor Converg.
 RF0849;SPC ME E     -   355,965.765   336,994.237   MT  0.99991682   +0 21 14.9

 HV8128;SPC MD       -   257,462.59  1,245,959.54   sFT  0.99998804   -0 08 43.1
 CK3919;SPC SC       -   342,482.46  2,008,965.76   iFT  0.99991459   +0 00 58.2
 FB2124;SPC TN       -   186,810.      805,260.      MT  (+/- 180 meters Scaled)
 RF0849;UTM  19      - 5,191,067.183   575,088.596   MT  0.99966930   +0 43 08.7

 FT1606;UTM  11      - 3,919,831.845   510,241.833   MT  0.99960129   +0 03 55.4
 FV1057;UTM  10      - 3,937,617.155   689,693.779   MT  1.00004345   +1 13 03.9


                                ***
 DATA ITEM: Combined Factor:
            for State Plane Coordinate System of 1983 (SPC)
            and/or Universal Transverse Mercator (UTM)
 DISPLAYED: Combined Factors are displayed for those horizontal control stations
            which have an SPC or UTM Scale Factor.
 COMMENTS : 
            As discusssed on p. 49 in NOAA Manual NOS NGS 5, 
                "State Plane Coordinate System of 1983";
            which is available at:
                http://www.ngs.noaa.gov/PUBS_LIB/pub_index.html
           The elevation factor is often combined with the grid scale factor of
           a line to form a single multiplier that reduces an observed horizontal
           distance at an average elevation directly to the SPCS grid. These two factors
           are quickly combined by obtaining the product of the factors. This product
           is approximated by subtracting "1" from the sum of the two factors. Identified
           as the "combined factor," when multiplied by the horizontal distance it
           has the same effect as each factor multiplied separately, yielding the
           grid distance.
  
          
 EXAMPLES :________________________________________________________________
 RF0849!             -  Elev Factor  x  Scale Factor =   Combined Factor
 RF0849!SPC ME E     -   0.99997420  x   0.99991682  =   0.99989102
 RF0849!UTM  19      -   0.99997420  x   0.99966930  =   0.99964351


                                ***
                                 
 DATA ITEM: Grid Azimuth for Primary Reference Object
 DISPLAYED: When Box Score is available.
 COMMENTS : The grid azimuth applies to the specified map projection only.
 EXAMPLES :________________________________________________________________
 RF0849:SPC ME E     -   CARIPORT AZ MK                           338 16 51.1
 RF0849:UTM  19      -   CARIPORT AZ MK                           337 54 57.3

                                ***
 DATA ITEM: Box Score
 DISPLAYED: When available for Old Horizontal Control marks.
 COMMENTS : Distance may be blank;  PID may be blank.
            There may be unadjusted marks not shown that are
            in the vicinity of the Old Horizontal Control mark.
            Contact NGS regarding their information.
 EXAMPLES :________________________________________________________________
 MC0588|---------------------------------------------------------------------|
 MC0588| PID    Reference Object                     Distance      Geod. Az  |
 MC0588|                                                           dddmmss.s |
 MC0588| MC1379 WESTON MUNICIPAL TANK               APPROX.14.8 KM 0024913.8 |
 MC0588| MC0587 FRANK RM 1                           36.576 METERS 10109     |
 MC0588|        HOYTVILLE N BALT GRAIN ELEV         APPROX. 3.0 KM 1400111.8 |
 MC0588| MC1373 MC COMB MUNICIPAL TANK              APPROX.11.7 KM 1753525.4 |
 MC0588| MC0586 FRANK AZ MK                                        1800257.9 |
 MC0588| MC0592 FRANK AZ MK 2                                      2563259.8 |
 MC0588| MC1376 DESHLER MUNICIPAL TANK              APPROX. 7.9 KM 2694631.8 |
 MC0588| MC0589 FRANK RM 2                           34.759 METERS 34452     |
 MC0588|---------------------------------------------------------------------| 

                                ***
 DATA ITEM: Superseded Survey Control
 DISPLAYED: When available.
 COMMENTS : Superceded control are previously published data control values
            that are obsolete but reprinted for continuity of records.  
            Format is similar to 'Current Survey Control',
            but is not marked with '*' in cc 8.
            AD means ADJUSTED, referring to horizontal position.
            GP means GPS_OBS,  referring to GPS derived ellipsoidal height.
            This is followed by an epoch date (if available).
            This is followed by Order (if available, Horizontal or Vertical),
            then is followed by Class (if available, Vertical only).

            A horizontal Order of 'c' is used for CORS stations.
            Superseded elevations have no epoch date but the
            Order and Class are displayed for bench mark heights.
            The determination text used for superseded elevations
            is identical to that used for the current survey control.
 EXAMPLES :___________________________________________________________________
 AA0000                          SUPERSEDED SURVEY CONTROL
 AA0000
 AB6382  NAD 83(CORS)-  31 52 26.11223(N)   102 18 54.55641(W) AD(1996.00) c  
 FV1057  NAD 83(1992)-  35 33 50.72286(N)   120 54 24.79262(W) AD(1991.35) 1  
 HW3152  NAD 83(1986)-  38 26 14.08939(N)   079 49 54.57180(W) AD(       ) 3  
 HW3152  NAD 27      -  38 26 13.66570(N)   079 49 55.35309(W) AD(       ) 3  
 TV1290  PR          -  18 28 33.07855(N)   066 48 04.76640(W) AD(       ) 2  
 TU3368  OLD HI      -  21 12 45.75000(N)   156 58 20.86500(W) AD(       ) 3  
 RF0849  ELLIP HT    -       164.56   (m)           (04/19/96) GP(1995.00) 3 1
 HV9260  ELLIP HT    -       131.19   (m)           (06/29/94) GP(       ) 4 1
 HV0454  NGVD 29     -         1.266  (m)           4.15   (f) ADJUSTED    1 2
 GW1440  NGVD 29     -       304.876  (m)        1000.25   (f) ADJ UNCH    2 0
 AA4380  NGVD 29     -       175.86   (m)         577.0    (f) LEVELING    3  
 FE2754  NGVD 29     -        84.07   (m)         275.8    (f) N HEIGHT    3  
 FV1057  NGVD 29     -       564.37   (m)        1851.6    (f) RESET       3  
 CA0570  NGVD 29     -       545.10   (m)        1788.4    (f) COMPUTED    1 2
 AA8531  NGVD 29     -        75.8    (m)         249.     (f) GPS OBS        
 UV2087  NGVD 29     -         6.8    (m)          22.     (f) VERT ANG       
 LX3119.No superseded survey control is available for this station.

                                ***
 DATA ITEM: U.S. NATIONAL GRID SPATIAL ADDRESS
 DISPLAYED: When available.
 COMMENTS : The U.S. National Grid System is an alpha-numeric reference  
            system that overlays the UTM coordinate system. It is a
            Federal Geographic Data Committee (FGDC) standard
            developed to improve public safety, commerce,
            as well as aid the casual GPS user.
            The USNG provides an easy to use geoaddress system for
            identifying and determining locations with the help of a
            USNG gridded map and/or a USNG enabled GPS system.

            To learn how to read USNG coordinates see:
            http://www.xyproject.org/
            and follow the link "US National Grid (USNG)"
            in the second paragraph.
              
            For further information about the U.S. National Grid System,
            see the Federal Geographic Data Committee's Standard
            for the United States Nation Grid at:
            http://www.fgdc.gov/standards/documents/standards/xy_proj/
            and select paper fgdc_std_011_2001_usng.pdf
 EXAMPLES :________________________________________________________________
 KF0798_U.S. NATIONAL GRID SPATIAL ADDRESS: 14SPJ8660324404(NAD 83)
 HV0454_U.S. NATIONAL GRID SPATIAL ADDRESS: 18SUH927451(NAD 83)

                                ***
 DATA ITEM: Mark Setting Information
 DISPLAYED: When available.
 COMMENTS : _ is used as an identifier for the data record.
            + is used as an identifier for a record continuation.
 EXAMPLES :________________________________________________________________
 RF0849_MARKER: DH = HORIZONTAL CONTROL DISK
 RF0849_SETTING: 7 = SET IN TOP OF CONCRETE MONUMENT (ROUND)
 RF0849_STAMPING: CARIPORT 1985
 RF0849_STABILITY: C = MAY HOLD, BUT OF TYPE COMMONLY SUBJECT TO
 RF0849+STABILITY: SURFACE MOTION

 RF0849_SATELLITE: THE SITE LOCATION WAS REPORTED AS SUITABLE FOR
 RF0849+SATELLITE: SATELLITE OBSERVATIONS - October 15, 1995

 PU1648_SATELLITE: THE SITE LOCATION WAS REPORTED AS NOT SUITABLE FOR
 PU1648+SATELLITE: SATELLITE OBSERVATIONS - August 19, 1991

                                ***
 DATA ITEM: Recovery History Records
 DISPLAYED: Always.
 COMMENTS : Landmarks will say 'FIRST OBSERVERED' rather than 'MONUMENTED'
            The Month/Day are displayed if available.
            Refer to the bluebook for recovery agency acronyms.
 EXAMPLES :________________________________________________________________
 MC0588  HISTORY     - Date     Condition        Recov. By
 MC0588  HISTORY     - 1943     MONUMENTED       CGS
 MC0588  HISTORY     - 1968     GOOD             NGS
 MC0588  HISTORY     - 1968     GOOD             CGS
 MC0588  HISTORY     - 1984     MARK NOT FOUND   USPSQD
 MC0588  HISTORY     - 19940826 GOOD             OH-063

                                ***
 DATA ITEM: Description and Recovery text
 DISPLAYED: When available.
 COMMENTS : Displayed chronologically.  The description format has evolved
            through time.  The authoritative reference for descriptions is
            the NGS bluebook, chapter three.  A current format is as follows.
            The phrases "DESCRIBED BY... " and "RECOVERY BY..." are inserted
            by NGS during processing.
            The first paragraph gives the general location of the station and
            the landowner and/or the person to contact for station access.
            The second paragraph gives a "to-reach". The to-reach begins at a
            well-known location that will remain through time, such as the
            junction of state, federal or interstate highways.   Legs along the
            the route are given as right or left turn, compass direction
            followed, road name if any, distance traveled in kilometers (miles),
            and leg terminating feature. The to-reach ends with the phrase,
            "TO THE STATION ON THE RIGHT/LEFT."
            The third paragraph first details the survey mark that is observed,
            then the monument in which the mark is set, then ties are given
            FROM features in the vicinity of the station TO the station, with
            horizontal distances reported to the closest 0.1 m (0.1 ft).
            A vertical tie is encouraged to assist with recovery of stations
            that may become buried.
            A fourth paragraph may be added to include notes, such as
            obstructions to GPS visibility or hazards of station occupation. 
 EXAMPLES :________________________________________________________________
 HU0680                          STATION DESCRIPTION
 HU0680
 HU0680 DESCRIBED BY COAST AND GEODETIC SURVEY 1942
 HU0680 1.5 MI SE FROM SALEM.
 HU0680 THIS MARK IS ABOUT 1.5 MILES SOUTHEAST OF THE JUNCTION WITH
 HU0680 HIGHWAY U.S. 50 ALONG A GRAVEL ROAD FROM SALEM, DORCHESTER COUNTY,
 HU0680 0.25 MILE NORTHEAST ALONG A DIRT ROAD TO THE FARM HOUSE, ABOUT
 HU0680 100 FEET NORTH OF THE STATION, 20 FEET NORTHEAST OF THE NORTHEAST
 HU0680 CORNER OF THE HOUSE, 1 FOOT WEST OF A WIRE FENCE ROW, AND IS A
 HU0680 STANDARD REFERENCE DISK SET IN THE TOP OF A CONCRETE POST.
 HU0680
 HU0680                          STATION RECOVERY (1988)
 HU0680
 HU0680 RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 1988
 HU0680 THE MARK IS LOCATED ABOUT 1.9 KM (1.20 MI) SOUTH OF THE SMALL COMUNITY
 HU0680 OF SALEM.  OWNERSHIP--EDGAR S. GORE, RD 1 BOX 85, VIENNA, MD. 21869.
 HU0680 PHONE (301) 228-2862.
 HU0680 TO REACH THE STATION FROM THE POST OFFICE IN LINKWOOD, GO SOUTHEAST ON
 HU0680 U.S. HIGHWAY 50 FOR 3.55 KM (2.20 MI) TO A SIDE ROAD RIGHT.  TURN
 HU0680 RIGHT AND GO SOUTHEAST ON SALEM ROAD FOR 0.85 KM (0.55 MI) TO A SIDE
 HU0680 ROAD RIGHT.  TURN RIGHT AND GO SOUTH ON RAVENWOOD ROAD FOR 1.90 KM
 HU0680 (1.20 MI) TO A SIDE ROAD LEFT.  TURN LEFT AND GO EAST ON A DIRT
 HU0680 DRIVEWAY FOR 0.42 KM (0.25 MI) TO THE MARK ON THE LEFT.
 HU0680 THE MARK IS A CGS TRIANGULATION DISK SET IN THE TOP OF A 0.3 M (1.0 FT)
 HU0680 SQUARE CONCRETE POST PROJECTING 0.13 M (0.4 FT) ABOVE THE GROUND.  THE
 HU0680 STATION IS LOCATED 15.7 M (51.5 FT) SOUTHWEST FROM THE SOUTHWEST EDGE
 HU0690 OF A CULTIVATED FIELD, 8.1 M (26.6 FT) SOUTH-SOUTHEAST FROM A 0.25 M
 HU0690 (0.8 FT) CHERRY TREE, 7.7 M (25.3 FT) NORTHEAST FROM THE NORTHEAST
 HU0690 CORNER OF A TWO STORY HOUSE AND 7.0 M (23.0 FT) NORTH FROM THE NORTH
 HU0690 CORNER OF A BLOCK BUILDING.

                                ***