Comparison of Signal Levels from GPS and WAAS
Posted: Sat Feb 06, 2016 10:57 pm
The signal levels provided to users' receivers from the Global Positioning System (GPS) and the Wide Area Augmentation System (WAAS) are specified in formal documents from each system provider, the U.S. Air Force (USAF) and the U.S. Federal Aeronautics Administration (FAA), respectively
For GPS, the interface specification document lists the minimum signal levels delivered as -158.5dBW for the L1 Coarse/Acquisition signal from Group II R/M/F satellites. See Chart 3-Va in http://www.gps.gov/technical/icwg/IS-GPS-200H.pdf
For WAAS, the FAA specifies the user signal level to be the same, -158.5dBW. See section 3.3.1.6 User-Received Signal Levels in http://www.gps.gov/technical/ps/2008-WAAS-performance-standard.pdf
This suggests that reception of the WAAS space-based augmentation signal (SBAS) will be at a level equivalent to the GPS L1 C/A signal. This only makes sense. For purposes of obtaining an augmented precision position fix, the WAAS signal is of little value if the GPS signal cannot be received, and vice-versa. This also suggests that if your GPS with WAAS receiver can receive signals from GPS satellites, it should also be able to receive signals from WAAS satellites.
There is one very significant difference in coverage: GPS coverage is global; WAAS coverage is only for North America (including Alaska and Hawaii).
For GPS, the interface specification document lists the minimum signal levels delivered as -158.5dBW for the L1 Coarse/Acquisition signal from Group II R/M/F satellites. See Chart 3-Va in http://www.gps.gov/technical/icwg/IS-GPS-200H.pdf
For WAAS, the FAA specifies the user signal level to be the same, -158.5dBW. See section 3.3.1.6 User-Received Signal Levels in http://www.gps.gov/technical/ps/2008-WAAS-performance-standard.pdf
This suggests that reception of the WAAS space-based augmentation signal (SBAS) will be at a level equivalent to the GPS L1 C/A signal. This only makes sense. For purposes of obtaining an augmented precision position fix, the WAAS signal is of little value if the GPS signal cannot be received, and vice-versa. This also suggests that if your GPS with WAAS receiver can receive signals from GPS satellites, it should also be able to receive signals from WAAS satellites.
There is one very significant difference in coverage: GPS coverage is global; WAAS coverage is only for North America (including Alaska and Hawaii).