Global Positioning System (GPS)

The Global Positioning System (GPS) is a constellation of 24 satellites operated and maintained by the U.S. Department of Defense. Each satellite contains a high precision atomic clock and several transmitters that constantly send radio signals back to Earth.

These signals communicate the satellite's unique identification code, health, and position in space. GPS rover and base station units in the field receive these satellite signals and use them to calculate position, velocity, and time data for features on Earth.

Comparing GPS Tools

This guidance document helps DNR program staff who are considering the use of GPS tools to collect feature location data. It presents several major issues and characteristics for staff to consider when comparing, and ultimately selecting, an appropriate GPS tool:

• Comparing Global Positioning System (GPS) Tools [PDF 177KB]

GPS Accuracy Report

This document summarizes the results of a statistical analysis of the positional accuracy of data collected with several recreational and mapping/resource grade GPS receivers widely used by DNR programs. The primary goal of this study was to provide DNR program staff with general guidance about many of their most frequently asked GPS accuracy questions:

• Global Positioning System (GPS) Accuracy Report [PDF 1.2MB]

Selective Availability Discontinued

As of midnight, 5/1/2000, the U.S. Department of Defense discontinued its intentional degradation of Global Positioning System (GPS) signals, a process known as selective availability (SA). Information about SA and implications of its discontinuation for GPS data collection is provided in the following report, prepared by staff in the DNR Enterprise Data Management Section:

• Selective Availability (SA) Discontinued [PDF]

Contact

For more information:

DNR Bureau of Technology Services.