Sunday, March 18, 2012

What is WAAS, and Do You Need it?

GPS Block IIIA satellite

The Wide Area Augmentation System, also called WAAS, is one of those things that gets tacked on to the side of the GPS box or bullet-pointed under the specifications of some GPS units. Most people don’t really pay it much mind as it tends to just look like yet another marketing ploy. Kind of like boasting tons of megapixels on phones–does it actually mean what you think it means?

What is WAAS?

I’m going to assume that you have a basic knowledge of how GPS works. For a brief refresher, the GPS system involves satellites and satellite gound stations which interpret the signals. However, due to atmospheric interference in the ionosphere and various other factors, the signals can become slightly degraded and incorrect. The WAAS system is intended to fix this.

WAAS is made up of a series of ground reference stations which act as an intermediary between your WAAS-enabled GPS and the actual satellite signal. It checks the signals based on other known information and corrects for error.

Who can use WAAS?

WAAS is basically a regional corrective system and only covers North America. However, many other countries actually have their own versions of WAAS and regional GPS correction such as Japan’s Multi-Functional Satellite Augmentation System (MSAS) and Europe’s Euro Geostationary Navigation Overlay Service (EGNOS).

Do you need WAAS?

Image courtesy of Garmin

Image courtesy of Garmin

Well, if you can get WAAS on your GPS device, then you definitely should. A lot of units actually come with WAAS enabled already so you likely won’t have to go out of your way to get this feature.

According to Garmin’s informational page and the fancy graphic to the right (which looks a little older so take it with a grain of salt), WAAS-enabled GPS devices will have around five times the accuracy of non-WAAS signals. Personally, I’d say that’s definitely worth your time, even if it is slightly less than five times.

Alternatively, units that can also use GLONASS, while not common, also will have improved accuracy over units without either.

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