Applications
The NASA GDGPS System was designed to support the most demanding real-time GPS applications, on a global scale, and in space. Below is a partial list of application areas where the GDGPS System has been used operationally.
Data Management for High Performance GPS Tracking Networks
The GDGPS System is being used to operate and control real-time GNSS data streaming from a vast global GPS tracking network, including the NASA GGN. Efficient real-time data transfer is enabled through remote data editing and data compression. Strong authentication schemes provide security against data tampering. Local copies of the collected measurements can be left in-situ to ensure full recovery of precision geodetic data. The data collected from the GDGPS network is shared with the scientific community through the archival services of the NASA CDDIS facility.
Precise Real-time Positioning and Orbit Determination
Mobile, airborne, and space users can be positioned in real-time with unparalleled accuracy with the User Module of the RTGx software, using the precise real-time GPS orbit and clock products of the GDGPS System. The GDGPS System has been used to provide operational positioning and orbit determination services to the following NASA and non-NASA missions and projects:
- NASA Shuttle Radar Topography Mission (SRTM) - Rapid orbit determination
- NASA Jason-1 - Rapid orbit determination for generation of near-real-time sea surface products
- NASA AirSAR - Real-time onboard positioning for DC-8 payload checkout and calibrations
- NASA UAV-SAR - Real-time onboard positioning for G-3 airplane autonomous repeat path control
- NASA Sentinel-6 - Real-time orbit determination and ground data processing system
- AFRL NTS-3 - Real-time orbit determination
GPS Performance Monitoring and Situational Assessment
Since the GDGPS System determines the real-time state of the GNSS constellations with unparalleled accuracy, we can assess the performance of the system, in absolute terms, and relative to its broadcast navigation message. From monitoring the integrity of the GPS constellation, to situational awareness for theaters of operations, to the support of critical operations world-wide, GDGPS has the unrivalled ability to assess the performance of the GPS navigation signals in real-time.
Real-time Environmental Monitoring
The GDGPS System provides centimeter-accurate real-time positioning of ground receivers, enabling the accurate detection of co-seismic ground motion and the timely determination of earthquake magnitude and the potential ensuing tsunamis. The System is also being used for the real-time sensing of global ionospheric total electron content (TEC) maps for the Air Force Weather Agency (AFWA). This capability is also being explored as a means to detect ongoing tsunamis through their induced perturbation on the state of the ionosphere.
Commercial Differential Systems
The GDGPS System produces differential corrections to the GPS broadcast ephemeris with very high accuracy and seamless global validity. Various GDGPS technology components and data products are being used by several commercial providers of premium global differential corrections. The legacy RTG software and algorithms are being used by the FAA's Wide Area Augmentation System (WAAS), its Japanese counterpart, MSAS, and the Indian GAGAN.
Assisted GPS Data Services
A complete set of A-GNSS data are available from the GDGPS System in support of the E911 mandate and various other telecommunications and positioning applications. Complete global coverage, and extremely high reliability resulting from the high level of system redundancy, provide unparalleled value for wireless carriers and GPS chip makers seeking high-performance A-GPS services in support of their mobile devices.