Official U.S. government information about the
Global Positioning System (GPS) and related topics
Augmentation Systems
A GPS augmentation is any system that aids GPS by providing accuracy, integrity, availability, or any other improvement to positioning, navigation, and timing that is not inherently part of GPS itself.
A wide range of different augmentation systems have been developed by both the public and private sectors.
To meet specific requirements, the U.S. government has fielded a number of publicly available GPS augmentation systems, including (but not limited to) the following systems.
Wide Area Augmentation System (WAAS)
WAAS, a regional space-based augmentation system (SBAS) operated by the Federal Aviation Administration (FAA), supports aircraft navigation across North America.
Although designed primarily for aviation users, WAAS is widely available in receivers used by other positioning, navigation, and timing communities.
FAA is committed to providing WAAS service at the performance levels specified in the GPS WAAS Performance Standard. FAA is improving WAAS to take advantage of the future GPS safety-of-life signal to provide even better performance.
The WAAS service is interoperable with other regional SBAS services, including those operated by Japan (MSAS), Europe (EGNOS), and India (GAGAN).
More Information:
- WAAS Page (faa.gov)
- WAAS Performance Data (faa.gov) -- live coverage maps, etc.
- GPS WAAS Performance Standard
Return to top of pageContinuously Operating Reference Stations (CORS)
The U.S. CORS network, managed by the National Oceanic and Atmospheric Administration, archives and distributes GPS data for precise positioning tied to the National Spatial Reference System.
Over 200 private, public, and academic organizations contribute data from almost 2,000 GPS tracking stations to CORS.
The Online Positioning User Service (OPUS) offers free post-processing of GPS data sets to the centimeter level using CORS information. CORS is also being modernized to support real-time users.
More Information:
Global Differential GPS (GDGPS)
GDGPS is a high accuracy GPS augmentation system developed by the NASA Jet Propulsion Laboratory (JPL) to support the real-time positioning, timing, and determination requirements of NASA science missions.
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).
More Information:
International GNSS Service (IGS)
IGS is a network of over 350 GPS monitoring stations from 200 contributing organizations in 80 countries.
Its mission is to provide the highest quality data and products as the standard for global navigation satellite systems (GNSS) in support of Earth science research, multidisciplinary applications, and education, as well as to facilitate other applications benefiting society.
Approximately 100 IGS stations transmit their tracking data within one hour of collection.
More Information:
Nationwide Differential GPS System (NDGPS)
NDGPS was a ground-based augmentation system that provided increased accuracy and integrity of GPS information to users on U.S. waterways.
As of June 30, 2020, all NDGPS service has been discontinued in accordance with the NDGPS Federal Register Notice USCG-2018-0133. With the rollout of the new GPS III satellites combined with the permanent termination of Selective Availability, DGPS is no longer deemed a necessary augmentation for close harbor approach.
More Information:
- DGPS Discontinuance (uscg.gov)
- Mar 2018: Public Notice on Discontinuance of NDGPS (federalregister.gov)
- Jul 2016 Public Notice on NDGPS Downsizing (federalregister.gov)
- Sept 2015 Presentation on Future of NDGPS (700 KB PDF)
- Aug 2015 Request for Public Comments on NDGPS Downsizing (federalregister.gov)
- Sept 2013 Presentation on Future of NDGPS (500 KB PDF)
- Apr 2013 Request for Public Comments on the Future of NDGPS (regulations.gov)
Other Augmentations
There are many other GPS augmentation systems available worldwide, both government and commercial. These systems use differential, static, or real-time techniques.
There are also systems that augment other global navigation satellite systems. The United States is cooperating with many other nations to ensure the interoperability of international augmentation systems with GPS and U.S. GPS augmentations.
