WGS84 vs NAD83: a little GPS simulation in gvSIG Mobile

According to this article, the difference between the WGS84 and the NAD83 datums is in the order of 1 meter. Unless one is in a context where highly-accurate coordinates are needed, it should be feasible to consider them equivalent. I have done a little test to see if that is actually the case using gvSIG Mobile 0.3.

From this nice American website I have downloaded and cropped an aerial image of the city of St Paul, MN (keeping the original SRS, which is EPSG:26915), and then I have created a NMEA simulation file, which contains the NMEA messages a GPS device would create during a little walk in the center of that city. Keep in mind that:

EPSG:26915 = NAD83, UTM, zone 15N
EPSG:32615 = WGS84, UTM, zone 15N


If we set the SRS to EPSG:32615 in gvSIG Mobile, then add the ECW image (EPSG:26915) and then perform a GPS simulation, the result is this:




As we can see, there is not a visible offset between the GPS track and the narrow path we can see in that park. You can download the ECW image and the NMEA simulation file from these links:

http://lucasdom.homelinux.org:4603/services/download?file=34234

http://lucasdom.homelinux.org:4603/services/download?file=34235

Send a message to juan_lucas_dr@yahoo.com if you have issues.

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