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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.
SP_SET is 'specific setting'
EXAMPLES :________________________________________________________________
AC3384_MARKER: DB = BENCH MARK DISK
AC3384_SETTING: 31 = SET IN A PAVEMENT SUCH AS STREET, SIDEWALK, CURB, ETC.
AC3384_SP_SET: DROP INLET APRON
AC3384_STAMPING: COL 15 1984 BSM
AC3384_MARK LOGO: FLDNR
AC3384_MAGNETIC: N = NO MAGNETIC MATERIAL
AC3384_STABILITY: D = MARK OF QUESTIONABLE OR UNKNOWN STABILITY
AC3384_SATELLITE: THE SITE LOCATION WAS REPORTED AS SUITABLE FOR
AC3384+SATELLITE: SATELLITE OBSERVATIONS - March 18, 2002
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.
***
