Geodetic Control Information on Passive Marks: Horizontal and Vertical Geodetic Control Data for the United States - National Geospatial Data Asset (NGDA) Geodetic Control Information on Passive Marks

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.

Provide a base of reference for latitude, longitude and height throughout the United States.

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Questions concerning this data may be addressed to the NGS Information Center (ngs.infocenter@noaa.gov)

For more information about the datasheet, see this PDF: https://www.ngs.noaa.gov/DATASHEET/dsdata.pdf

All values were obtained from the NGA Datasheetavailable at <https://www.ngs.noaa.gov/datasheets/>

The distributor does not assume liability

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These data can be downloaded via several different search methods listed below:

PIDs (Permanent IDentifier) - http://www.ngs.noaa.gov/FORMS/help_pid.html

CORS SiteID - 4-character identification for a CORS site.

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Project Identfier

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Geodetic Data are in the public domain, not restricted from access or distribution.

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.

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The data was extracted from NGS datasheets which are available at https://www.ngs.noaa.gov/datasheets/ The NGS datasheet is a text document which summarizes key geodetic information stored in the NGS database.

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 attributesHD_HELD1, HD_HELD2, or SCALED.These lesser quality positions are described at:http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=SCALEDVertical 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,COMPUTEDLesser quality Orthometric Heights may also be preset in the dataset.These are identified by a ELEV_SRCE attributesGPS_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=SCALEDIMPORTANT - 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=SCALEDfor a description of the various type of methods used in determiningthe 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 moredetailed 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 Value: 95 percent confidence level for geodetic quality data. | Quantitative Test Explanation: 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.

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.; Quantitative Value: .05 meters, Test that produced the value: 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 Horizontal Positional Accuracy Value: .05 meters for highest order of accuracy

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).; Quantitative Value: .05 meters, Test that produced the value: 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%20ORDEREllipsoid 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 Vertical Positional Accuracy Value: .05 meter for highest order of accuracy

This dataset DOESN' T include destroyed marks. All other non-publishable marks are NOT included. Non-publishable criteria is available athttp://www.ngs.noaa.gov/cgi-bin/craigs_lib.prl?HELP_NONPUB=1

FGCS sponsored testing in cooperation with equipment manufacturers and National Institutes of Standards and Technology, Gaithersburg, MD 20850