SBAS (WAAS) and NDGPS Accuracy and Statistics

SBAS (WAAS) and NDGPS Accuracy and Statistics

October 20, 2010 By: Eric Gakstatter

There's something I've been wanting to write about since the ION-GNSS
conference a few weeks ago. However, a nasty cold, a 10-day trip to
Europe (INTERGEO conference), and some jet lag have kept me from it
until now.

Here goes.

First of all, most of the presentations from the CGSIC meeting are
available on the USCG Navigation Center website. You can view them by
clicking here. There's some very good reading and most of it is pretty
light-weight and in PDF format.

One of the presentations at the CGSIC (Civil GPS Service Interface
Committee) meeting during the ION-GNSS conference was "Integrating NDGPS
and SBAS —
An Optimal Real-time GPS Mapping Solution," presented by Jean-Yves
Lauture of Geneq, Inc.

I'm publishing two of the slides from his presentation in order to:

Show the accuracy potential of WAAS and NDGPS given a high performance
L1 receiver.
Discuss the statistical names/values used to express GPS accuracy.
First of all, each of the slides below are at the same scale. Each
ellipse is 20 cm with the outside limit (radius) being one meter.

I've known for quite sometime that SBAS (WAAS in this case) is capable
of sub-meter precision with a single-frequency GPS receiver. These
results are a bit better than what I've seen personally, and keep in
mind it's a limited data set of 1,800 continuous epochs, but impressive
none the less. Also, keep in mind that the WAAS Performance Analysis
Report published quarterly by the FAA's National Satellite Test Bed
shows the 95% horizontal accuracy value for Denver, Colorado, (near
where this data was collected) being .547 meters for the quarter ending
June 30, 2010 (7,856,354 samples collected over three months).

See:
http://www.gpsworld.com/survey/sbas-waas-and-ndgps-accuracy-and-statistics-10631