Proposal for Geospatial Positioning Accuracy Standards

Project Title

Geospatial Positioning Accuracy Standards

Submitting Organization

Methodology Work Group, Federal Geodetic Control Subcommittee


To provide consistency in reporting the accuracy of point geospatial data collected by different activities (e.g., geodetic surveying, topographic mapping, bathymetric mapping, facilities management mapping, cadastral surveying, etc.) and develop a FGDC document with a single methodology that defines how to report the positional accuracy for all point geospatial data collected, produced, or disseminated by the Federal government and the Nation.

Scope of Project

This project only pertains to developing a reporting methodology for the accuracy of point spatial data. It does not involve other standards aspects of point spatial data, e.g., data transfer, data collection, etc. This project involves all FGDC subcommittees and/or work groups since all spatial data will contain a statement describing the accuracy of these point data. While all of FGDC will be involved in developing the specifics of their individual data accuracy, a single overriding methodology is desired. This standard applies to point-specific data only, not other types of accuracy such as for area, lines, attributes, and raster data.


As stated in Executive Order 12906, dated April 13, 1994, FGDC shall coordinate the Federal Government's development of the National Spatial Data Infrastructure (NSDI). The Executive Order is intended to strengthen and enhance the general policies described in OMB Circular No. A-16.

This standard supports the development of the NSDI in a consistent manner by providing a means to directly compare the reported positional accuracy of spatial data obtained by one method (e.g., a cartographically-derived value) with the reported positional accuracy of spatial data obtained by another method (e.g., a GPS geodetic network survey) for the same point. Therefore, there must be consistency between parts of this document.

This standard also meets the general FGDC responsibility stated in OMB Circular No. A-119 for developing standards for implementing the NSDI, in consultation and cooperation with State, local, and tribal governments, private and academic sectors, and, where feasible, the international community. It also meets the responsibilities stated in OMB Circular No. A-16 to develop standards through FGDC to ensure that the spatial data produced by all agencies are compatible.

A single classification scheme will not fit the diverse types of point data collected or produced by every geospatial activity. Each point data activity listed in this document will describe how its application uses the same general accuracy standard to develop a reporting classification scheme for the particular type of point data. This will permit using the same general accuracy standard to describe all point data types.

The FGDC Standards Working Group is responsible for coordinating standards development; a single general accuracy standard and a single document describing the accuracy standards for each type of spatial data will ensure that there is consistency within the reported accuracy of these data.

Methodology Description: FGCS will develop the following sections of this document:


FGCS will also incorporate "parts" from other FGDC subcommittees and work groups and maintain the overall document. FGCS will provide assistance to other subcommittees and work groups developing their "parts" of the standard and review the overall document to ensure that it maintains consistency.

Each FGDC subcommittee or work group that collects point spatial data is responsible for developing their "part" and submitting it to FGCS through the FGDC Standards Working Group (SWG). The FGDC subcommittee or work group that developed their "part" is responsible for maintaining it.

SWG is responsible for coordinating development of other "parts" with FGDC subcommittees and work groups and the review of each new "part." Each new "part" must be approved by SWG before FGCS will incorporate it into the overall document.

Guidance for the contents of each "part" is provided in the INTRODUCTION AND REPORTING METHODOLOGY section.


A consistent method for reporting the accuracy of point spatial data as directed by Executive Order 12906 and OMB Circular No. A-16.

Potential Participants

Currently, the following FGDC subcommittees and work group have indicated their willingness to submit "parts":

    Geodetic Subcommittee
    Base Cartography Subcommittee
    Bathymetric Subcommittee
    Facilities Work Group
    Cadastral Subcommittee

Other subcommittees and work groups should be encouraged to submit their "parts."

Each subcommittee or work group is encouraged to utilize other groups external to FGDC (e.g., ACSM, URISA, ASPRS, ASCE, etc.) during the development of their "part." These groups may participate in the initial development and/or provide comments on draft versions. It is important to include these groups during the development stages and initial reviews to gain their support and minimize the number of changes resulting from the formal external review process.

Development and Completion Schedule

The following sections have been developed and approved by the Federal Geodetic Control Subcommittee:


These sections need review and approval by FGDC SWG.

The other "parts" that have been already agreed upon need to be drafted and approved by their respective subcommittees or work groups. Completion dates are dependent on these subcommittees or work groups who have provided the following target dates:

    (target date: __/9_)
    (target date: __/9_)
    (target date: __/9_)

When the other "parts" are completed, they can be issued as additions to the original document.

It is recommended that the document be initially issued with:



Existing resources were adequate for FGCS to develop the following sections: INTRODUCTION AND REPORTING METHODOLOGY and 1 GEODETIC NETWORKS. Existing resources are adequate for FGCS to maintain these two "parts" and maintain the overall document. It is unknown if resources are available to the other participating FGDC subcommittees and working groups to see the timely completion of this standard (with all its parts) through all 15 FGDC standards process steps.

Relationship to Other Standards

Coordinated Federal geospatial positioning accuracy standards for all levels of accuracy do not currently exist. The standards developed under this proposal will provide consistency in reporting the accuracy of point geospatial data collected using diverse methodologies.

There are existing FGCS standards that deal with geodetic positioning accuracy. However, they need to be revised because they do not fully describe current positioning technology, i.e., GPS. These accuracy standards will supersede existing FGCS accuracy standards (e.g., B-order, first-order, second-order, etc.).

FGCS developed this standard in conjunction with our counterparts at the Geodetic Survey of Canada. Both accuracy standards for geodetic networks are consistent.

FGCS developed this standard prior to having the ISO accuracy standard for geodetic networks. A subsequent comparison between the two standards revealed consistency in some areas (e.g., local accuracy versus relative accuracy) but differences in other areas (e.g., network accuracy versus absolute accuracy).