Geospatial Positioning Accuracy Standards, Part 3: National Standard for Spatial Data Accuracy

Document number


Maintenance authority

U.S. Geological Survey


The objective is to facilitate sharing and interoperability of geospatial data by providing a flexible and inclusive standard for testing and reporting accuracy of maps and geospatial data. 


The National Standard for Spatial Data Accuracy (NSSDA) implements a well-defined statistic and testing methodology for positional accuracy of maps and geospatial data derived from sources such as aerial photographs, satellite imagery, or maps. Accuracy is reported in ground units. The testing methodology is comparison of data set coordinate values with coordinate values from a higher accuracy source for points that represent features readily visible or recoverable from the ground. While this standard evaluates positional accuracy at points, it applies to geospatial data sets that contain point, vector, or raster spatial objects. Data content standards, such as FGDC Standards for Digital Orthoimagery and Digital Elevation Data, will adapt the NSSDA for particular spatial object representations. 

The standard insures flexibility and inclusiveness by omitting accuracy metrics, or threshold values, that data must achieve. However, agencies are encouraged to establish "pass-fail" criteria for their product standards and applications and for contracting purposes. Ultimately, users must identify acceptable accuracies for their applications. 

Ground coordinates of points established according to Federal Geodetic Control Subcommittee (FGCS) draft Standards for Geodetic Control Networks and process specifications are used in the National Spatial Reference System (NSRS) control network. NSRS ground control may be used to reference project control surveys to a common georeference system. The accuracy of spatial data derived from control surveys is expressed using the NSSDA. The NSSDA may also be related to FGCS Standards for Geodetic Networks by using NSRS points to test the accuracy of geospatial data. Both the NSSDA and Standards for Geodetic Networks will be integrated into a multipart FGDC Geospatial Positioning Accuracy Standard.

Sponsored by

Subcommittee for Base Cartographic Data (retired)

Project history

Proposal     FGDC Standards Working Group
Draft     1996-12 FGDC Standards Working Group 
Comment adjudication log     1998-04 FGDC Steering Committee 
FGDC-endorsed standard    1998 FGDC Steering Committee 
Proposal for revision     2003-11-17 FGDC Standards Working Group 


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