National Academies Press: OpenBook

The Global Positioning System: A Shared National Asset (1995)

Chapter: Challenges to Full GPS Utilization

« Previous: Current and Future Applications and Requirements
Suggested Citation:"Challenges to Full GPS Utilization." National Research Council. 1995. The Global Positioning System: A Shared National Asset. Washington, DC: The National Academies Press. doi: 10.17226/4920.
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Page 45

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GPS APPLICATIONS AND REQUIREMENTS 45 Table 2-7 Current and Future GPS Requirements for GIS, Mapping, Surveying, and Geodesya Application Accuracy (2 drms) Integrity Availability Coverage Time to Alarmb Geographic Information 1.0-10.0 m Minutes 98% Worldwide Systems (GIS) Photogrammetry 0.02-0.05 m Minutes 98% Worldwide Remote Sensing 0.1-20.0 m Not specified 98% Worldwide Geodesy 0.01-0.05 m Hoursc 98% Sites Worldwide Mapping 0.1-10 m Hoursc 98% Sites Worldwide Surveying Hydrographic 0.05-10.0 m Hoursc 98% Sites Worldwide Topographic 0.01-0.5 m Hoursc 98% Sites Worldwide Boundary 0.01-0.05 m Hoursc 98% Sites Worldwide a. Integrity (1 minus PHE times PMD), continuity of service, and resistance to RF interference requirements are not defined for mapping, survey, and geodetic applications. Source of other requirements, unless otherwise annotated: The Ohio State University, Center for Mapping. b. Source of time-to-alarm requirements: A Technical Report to the Secretary of Transportation on a National Approach to Augmented GPS Services, p. 13. c. The integrity of the positioning data for each of these applications is validated in post-processing. Challenges to Full GPS Utilization It is important to understand that nearly all accuracy requirements presently can be met using DGPS. However, the cost of meeting these requirements would decrease if various enhancements to the basic GPS itself were implemented. In particular, eliminating SA and/or A-S would drive down the costs of new applications. GIS applications would benefit most from the elimination of SA because many GIS requirements could potentially be satisfied by the accuracies obtained from stand-alone GPS with SA set to zero and with other potential accuracy improvements. All real-time, dynamic surveying and mapping applications would benefit from improved signal acquisition. Faster integer ambiguity resolution, important to real-time kinematic survey and mapping applications, would be achievable with a second frequency unencrypted by A-S. As discussed in Appendix G, access to the wider bandwidth of the P-code, which is approximately 20 MHz (versus 2 MHz for the C/A-code), also would increase resistance to RF interference and reduce vulnerability

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The Global Positioning System (GPS) is a satellite-based navigation system that was originally designed for the U.S. military. However, the number of civilian GPS users now exceeds the military users, and many commercial markets have emerged. This book identifies technical improvements that would enhance military, civilian, and commercial use of the GPS. Several technical improvements are recommended that could be made to enhance the overall system performance.

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