Realtime Position Accuracy to Within 10 Centimeters

The Global Differential GPS (GDGPS) System is a real-time GNSS monitoring and augmentation system that provides location information to about 3-inch position accuracy.

They use a large ground network of real-time reference receivers, innovative network architecture, and real-time data processing software, the GDGPS System provides sub-decimeter (less than 10 cm) positioning accuracy and sub-nanosecond time transfer accuracy anywhere in the world, on the ground, in the air, and in space, independent of local infrastructure.

Comtech provides emergency locator information using GDGPS for about half of cell phone owners in the United States, as well as millions of others around the world.

Comtech computes more than 10 billion locations per month around the world.

They provided the basis for the Federal Aviation Administration’s Wide Area Augmentation System (WAAS), used by tens of thousands of planes for navigation and guided landing in North America. WAAS and its implementations in Japan and India are based on the Real Time GIPSY software JPL enhanced with support from Raytheon and the FAA.

GDGPS has also enabled modern automated precision agriculture.

The core of the GDGPS tracking network is a JPL-owned and operated network of 75+ geodetic-quality, tripple frequency receivers, distributed globally. Additional real-time sites are contributed by a variety of U.S. and international partner organizations. The result is the world’s largest real-time GPS tracking network, with more than 200 global sites. All these sites stream their GPS measurements at 1 Hz to the GDGPS Operation Centers (GOCs), where it is processed and analyzed in real-time.

Employing the largest global real-time tracking network, the Global Differential GPS (GDGPS) System tracks the GNSS civil signals on the L1, L2, and L5 frequencies. Highly redundant satellite coverage (25 fold for GPS, 18 fold for GLONASS, on average) ensures seamless and robust global coverage. The raw measurements are streamed via redundant communication paths to three geographically-separate GDGPS Operation Centers (GOC).

In the US, GBAS (Ground-based GPS Augmentation) comes with the following costs. An installed Cat. 1 GBAS costs $3-4 million; and $700,000 more for Cat. 2.

Future NASA plans include using the Tracking and Data Relay Satellite System (TDRSS) to disseminate via satellite a real-time differential correction message. This system is referred to as the TDRSS Augmentation Service Satellites (TASS).

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