[LEAPSECS] GPS certified for navigation?

Jonathan E. Hardis jhardis at tcs.wap.org
Thu Sep 23 20:45:45 EDT 2010

On Sep 23, 2010, at 3:35 PM, Steve Allen wrote:

> for robustness against the ionosphere (mostly for surveying) see WAAS

> http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System

As the link makes clear, WAAS is funded by the FAA "for aircraft," not
"for surveying."

Aircraft and surveying have opposite needs in GPS augmentation
systems. For aircraft, the primary issue is prompt warning if
something went flakey on the GPS signal. For surveying, the primary
issue is achieving cm-level horizontal resolution. To do that,
surveyors use "real-time networks" of monitoring stations at fixed
locations. Many of these are local and cooperatively organized, like
the ones in Washington State (http://www.prsn.org/) and Oregon (http://www.theorgn.org/
). With a communications channel from the network to the surveying
site, cm-level resolution can be obtained in real time. Otherwise,
the surveying data can be post-processed. Compared to the needs of
aircraft (collision avoidance), surveying is much more fault-tolerant.

- Jonathan

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