Editing Wide Area Augmentation System (section)

==Drawbacks and limitations==
For all its benefits, WAAS is not without drawbacks and critical limitations:

* [[Space weather]]. All man-made satellite systems are subject to space weather and space debris threats. For example, a solar super-storm event composed of an extremely large and fast earthbound [[coronal mass ejection]] (CME) could disable the geosynchronous or GPS satellite elements of WAAS.
* The broadcasting satellites are geostationary, which causes them to be less than 10° above the horizon for locations north of 71.4° latitude. This means aircraft in areas of [[Alaska]] or [[northern Canada]] may have difficulty maintaining a lock on the WAAS signal.<ref>Department of Aeronautics and Astronautics, Stanford University. [http://waas.stanford.edu/~wwu/papers/gps/PDF/LoPLANS02.pdf WAAS Performance in the 2001 Alaska Flight Trials of the High Speed Loran Data Channel] {{webarchive|url=https://web.archive.org/web/20060427104555/http://waas.stanford.edu/~wwu/papers/gps/PDF/LoPLANS02.pdf |date=2006-04-27 }}. Accessed June 12, 2006.</ref>
* To calculate an ionospheric grid point's delay, that point must be located between a satellite and a reference station. The low number of satellites and ground stations limit the number of points which can be calculated.
* Aircraft conducting WAAS approaches use certified GPS receivers, which are much more expensive than non-certified units. In 2024, Garmin's least expensive certified receiver, the GPS 175, had a suggested retail price of US$5,895.
* WAAS is not capable of the accuracies required for Category II or III ILS approaches. Thus, WAAS is not a sole-solution and either existing ILS equipment must be maintained or it must be replaced by new systems, such as the [[local-area augmentation system]] (LAAS).<ref>Federal Aviation Administration. [http://gps.faa.gov/FAQ/faq-waas.htm WAAS FAQ] {{webarchive|url=https://web.archive.org/web/20060517035105/http://gps.faa.gov/FAQ/faq-waas.htm |date=2006-05-17 }}. Accessed June 12, 2006.</ref>
* WAAS Localizer Performance with Vertical guidance (LPV) approaches with 200-foot minimums (LPV-200) will not be published for airports without medium intensity lighting, precision runway markings and a parallel taxiway. Smaller airports, which currently may not have these features, would have to upgrade their facilities or require pilots to use higher minimums.<ref name="AOPA_welcomes_WAAS" />
* As precision increases and error approaches zero, the [[navigation paradox]] states that there is an increased collision risk, as the likelihood of two craft occupying the same space on the shortest distance line between two navigational points has increased.