National Geodetic Survey (NGS) Geodetic Control Stations, (Horizontal and/or Vertical Control), March 2009
Dataset Identification:
Resource Abstract:
This data contains a set of geodetic control stations maintained by the National Geodetic Survey. Each geodetic control station
in this dataset has either a precise Latitude/Longitude used for horizontal control or a precise Orthometric Height used for
vertical control, or both. The National Geodetic Survey (NGS) serves as the Nation's depository for geodetic data. The NGS
distributes geodetic data worldwide to a variety of users. These geodetic data include the final results of geodetic surveys,
software programs to format, compute, verify, and adjust original survey observations or to convert values from one geodetic
datum to another, and publications that describe how to obtain and use Geodetic Data products and services.
Citation
Title National Geodetic Survey (NGS) Geodetic Control Stations, (Horizontal and/or Vertical Control), March 2009
The geographic limits of USA including trust Territories
thesaurus name >
Title None
purpose:
Provide a base of reference for latitude, longitude and height throughout the United States.
Resource language:
eng; USA
Resource progress code:
complete
Resource Maintenance Information
maintenance or update frequency:
unknown
Constraints on resource usage:
Legal Constraints
Access Constraints
otherRestrictions
use constraint:
otherRestrictions
Other constraints
Access Constraints: Geodetic Data are in the public domain, not restricted from access or distribution. . Use Constraints:
Not restricted; Geodetic Data, including software were developed and compiled with U.S. Government funding; no proprietary
rights may be attached to them nor may they be sold to the U.S. Government as part of any procurement of ADP products or services.
Spatial representation type code:
vector
Processing environment:
Microsoft Windows 2000 Version 5.2 (Build 3790) Service Pack 2; ESRI ArcCatalog 9.3.1.1850
Resource extent
Geographic Extent
Geographic Bounding Box
westBoundLongitude
-109.056738
eastBoundLongitude
-103.002383
northBoundLatitude
37.0
southBoundLatitude
31.332258
Temporal Extent
retrieval date
2009-02-12
Credits:
NOAA, National Geodetic Survey and cooperating organizations
point of contact
-
pointOfContact
position Name IT Specialist
Contact information
Telephone
Voice 301-713-3257x152
Fax 301-713-4172
Address
SSMC2/9152 1315 East-west Highway, Silver Spring, MD, 20910
Country USA
description The National Geodetic Survey produces geodetic data. Geodetic data comprise the results of geodetic surveys to determine,
among other things, latitude, longitude, height, scale, and orientation control. The National Geodetic Survey original field
survey project observations and final reports are accessioned into records system of the National Archives and Records Administration
of the U.S.A. These surveys provide information valuable for a variety of uses in the mapping, charting and surveying community.
The NGS' final product is the geodetic data sheet. Geodetic data sheets are comprehensive summaries of all published information
for a given geodetic reference point, including: the geographic position and/or height based on the current reference datum,
condition of the survey mark when it was last visited, a description of where the point is located and how to reach it, and
an explanation of the terms used in the data sheet. In support of these geodetic data, the NGS provides software, publications,
and various user services, including geodetic advisor program, instrument calibration, surveying standards, and technical
workshops. This dataset contains certain information extracted from the above mentioned data sheet.
processing agent contact
-
processor
position Name IT Specialist
Contact information
Telephone
Voice 301-713-3257x152
Fax 301-713-4172
Address
SSMC2/9152 1315 East-west Highway, Silver Spring, MD, 20910
Country USA
source description
The geodetic data must be submitted in the digital formats specified in the FGCS (formally FGCC) publication "Input Formats
and Specifications of the National Geodetic Survey Data Base" which describes the formats and procedures for submission of
data for adjustment and assimilation into the National Geodetic Survey Data Base. Separate volumes of this publication refer
to horizontal (volume 1), vertical (volume 2), and gravity (volume 3) control, and are available from NOAA, National Geodetic
Survey, 1315 East-West Hwy, Code N/CGS1, Silver Spring, MD, 20910 (1-301-713-3242). Note guidelines for submission of three-dimensional
Global Positioning System (GPS) relative positioning data are contained in annex L to volume 1.
representative resolution scale:
Scale denominator:
source citation
Title "Input Formats and Specifications of the National Geodetic Survey Data Base" published by FGCS (formally FGCC)
alternateTitle
Blue Book
publication Date
2009-02-12T00:00:00
cited responsible party
-
resourceProvider
organisation Name
NOAA, National Geodetic Survey
Resource extent
Temporal Extent
publication date
1994-01-01
AbsoluteExternalPositionalAccuracy
name Of Measure Horizontal Positional Accuracy
measure Description
Horizontal positional accuracy statements pertain to horizontal control stations only. i.e. Those with geodetic quality Latitude,
Longitudes. Positional Accuracy explanation contained in "Geometric Geodetic Accuracy Standards and Specifications For Using
GPS Relative Positioning Techniques," FGCS (formally FGCC) publication version 5.0, 1989, (See table 1, p6). with the exception
of Order A and Order B which have an accuracy of as described at: http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=HORZ%20ORDER
evaluation Method Description
The description of tests are explained in "Geometric Geodetic Accuracy Standards and Specifications For Using GPS Relative
Positioning Techniques," FGCS (formally FGCC) publication version 5.0, 1989. .05 meters for highest order of accuracy.
Quantitative Result
result value .05
value Units
AbsoluteExternalPositionalAccuracy
name Of Measure Vertical Positional Accuracy
measure Description
Vertical positional accuracy statements pertain to vertical control stations only. i.e. Those with geodetic quality Orthometric
Heights. Orthometric Height accuracy explanation is contained in FGDC publication "Standards and Specifications for Geodetic
Control Networks" with the exception of vertical control of class 0 POSTED and READJUSTED Heights which are described at:
http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=VERT%20ORDER Ellipsoid height accuracy explanation contained in "Geometric
Geodetic Accuracy Standards and Specifications for Using GPS Relative Positioning Techniques," FGCS (formally FGCC) publication
version 5.0, 1989. (see table 1, p6). The accuracies for ellipsoid heights are described at: http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=ELLP%20ORDER
evaluation Method Description
The description of tests are explained in "Geometric Geodetic Accuracy Standards and Specifications for Using GPS Relative
Positioning Techniques," FGCS (formally FGCC) publication version 5.0, 1989, (See table 1, p6). .05 meters for highest order
of accuracy
Quantitative Result
result value .05
value Units
Completeness Commission
ConceptualConsistency
measure Description
FGCS sponsored testing in cooperation with equipment manufacturers and National Institutes of Standards and Technology, Gaithersburg,
MD 20850
QuantitativeAttributeAccuracy
name Of Measure Quantitative Attribute Accuracy Assessment
measure Description
Geodetic Data are continuously being processed; their standards and specifications are being reviewed for next publication
release. "Standards and Specifications for Geodetic Control Networks", 1984 and "Geometric Geodetic Accuracy Standards and
Specifications for Using GPS Relative Positioning Techniques," FGCS (formally FGCC) publication version 5.0 1989, are most
current published documents.
evaluation Method Description
Horizontal control stations (those with precise Latitude, Longitude) were established in accordance with FGDC publications
"Standards and Specifications for Geodetic Accuracy Standards" and "Geometric Geodetic Accuracy Standards and Specifications
for Using GPS Relative Positioning Techniques" The final Latitude, Longitude of these stations were determined by a least
squares adjustments of the horizontal observations. Horizontal control station have Latitude, Longitudes displayed to 5 places
and are identified by attribute POS_SRCE = 'ADJUSTED' Lesser quality Latitude, Longitudes may also be preset in the dataset.
These are identified by a POS_SRCE attributes HD_HELD1, HD_HELD2, or SCALED. These lesser quality positions are described
at: http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=SCALED Vertical control stations (those with precise Orthometric Heights)
were established in accordance with FGDC publications "Standards and Specifications for Geodetic Accuracy Standards" The final
Orthometric Height of these stations were in most cases determined by a least squares adjustments of the vertical observations
but in some cases may have been keyed from old survey documents. Vertical control stations have Orthometric Heights displayed
to 2 or 3 places and are identified by attribute ELEV_SRCE of ADJUSTED, ADJ UNCH, POSTED,READJUST,N HEIGHT,RESET,COMPUTED
Lesser quality Orthometric Heights may also be preset in the dataset. These are identified by a ELEV_SRCE attributes GPS_OBS,
VERT_ANG, H_LEVEL, VERTCON, SCALED. These lesser quality orthometric heights are described at: http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=SCALED
IMPORTANT - Control stations do not always have both precise Latitude, Longitude AND precise Orthometric Height. A horizontal
control station may have a orthometric height associated with it which is of non geodetic quality. These types of heights
are displayed to 0, 1, or 2 decimal places. Worst case being off by +/- 1 meter. LIKEWISE - A Vertical control station may
have a Latitude, Longitude associated with it which is of non geodetic quality. These types of Latitude, Longitudes are displayed
to 0, 1 or 2 decimal places. Worst case being off by +/- 180 meter. Refer to http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=SCALED
for a description of the various type of methods used in determining the Latitude, Longitude, and Orthometric Height. Attribute
POS_CHECK and ELEV_CHECK indicate whether or not an observational check was made to the position and/or orthometric height.
Care should be taken when using "No Check" coordinates. If attribute ELEV_SRCE = 'VERTCON' then the Orthometric Height was
determined by applying NGS program VERTCON to an Old NGVD 29 height. In most areas VERTCON gives results to +/- 2 cm. See
http://www.ngs.noaa.gov/TOOLS/Vertcon/vertcon.html for a more detailed explanation of VERTCON accuracy. Ellipsoid Heights
are also present in the dataset. The ellipsoid heights consist of those determined using a precise geoid model, which are
displayed to 2 decimal places and are considered good to +/- .005 meters, and those displayed to 1 decimal place and are considered
only good to +/- .5 meters
Quantitative Result
result value 95 percent confidence level for geodetic quality data.