National Academies Press: OpenBook

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

Chapter: Accuracy Improvements by Incorporating Satellite Ranging Data into Ground Solution

« Previous: Planned Block IIR Operation
Suggested Citation:"Accuracy Improvements by Incorporating Satellite Ranging Data into Ground Solution." National Research Council. 1995. The Global Positioning System: A Shared National Asset. Washington, DC: The National Academies Press. doi: 10.17226/4920.
Page 109

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

PERFORMANCE IMPROVEMENTS TO THE EXISTING GPS CONFIGURATION 109 exchanging clock and ephemeris information every 15 minutes via UHF communications crosslinks, which will connect each satellite in the constellation to all of the other satellites in view, each satellite will have knowledge of the ephemeris and clock information of all the satellites in the constellation. Based on the 15-minute ranging data exchanged, the Block IIR satellites can autonomously update the navigation message being broadcast to users. The current plan for testing the autonomous ranging capability is initially to download the 15-minute ranging data from each satellite's Kalman Filter once per day to the OCS so that it can be compared with the ground-based data derived from the MCS's Kalman Filter. After successful testing of autonomous satellite ranging capability is completed, clock and ephemeris corrections will be determined with the on-board Kalman Filter, and the satellites will automatically update the navigation message every hour. However, even with autonomous generation of clock and ephemeris corrections, the Air Force plans to continue daily uploads of the satellites' clock offset relative to UTC.49 After 24 hours, the combined clock and ephemeris error for the Block IIR satellite constellation is expected to be 1.9 meters (ls).50 Suggested Improvements Using the Autonomous Ranging and Crosslink Communication Capability Current plans call for the use of the Block IIR satellite crosslink capability only for specific commands related to SA and autonomous navigation. Further improvements in accuracy, system reliability, and integrity could be obtained by exploiting the satellite ranging data obtained during the 15-minute autonomous ranging cycles and by more effectively utilizing the communication crosslinks. These improvements are discussed below. Accuracy Improvements by Incorporating Satellite Ranging Data into Ground Solution Since the satellite ranging data will initially be sent to the OCS for comparison with the ground-based data, the space-based measurements also could be incorporated into the MCS's Kalman Filter. By uploading these integrated corrections to the satellites, an incremental improvement in accuracy can be achieved over the initial planned Block IIR operational procedure, where the satellites will be uploaded with only ground-based clock and ephemeris corrections. When autonomous satellite ranging capability has been activated, further accuracy improvements could be achieved if the integrated corrections were sent to satellites at least once per day. Ideally, one satellite could be sent the corrected data every hour and the crosslinks could be used to relay the information to all the other satellites. These integrated 49 Source: Input provided to the NRC committee by Capt. Christopher Shank and Capt. Earl Pilloud, Air Force Space Command, January and February 1995. 50 Response from Martin Marietta Astro Space Division of Lockheed-Martin, 6 February 1995.

Next: Ground-Based Integrity Improvements »
The Global Positioning System: A Shared National Asset Get This Book
Buy Paperback | $61.00 Buy Ebook | $48.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

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.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook,'s online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!