I've heard that we could use two or more handheld GPS to get a better positioning accuracy using post processing techniques. Anybody can tell me the methodology? Also, can we program handheld GPS such that it records coordinates every second?
[GIS] Using handheld GPS for sub-meter precise positioning
gpsqgis-processing
Best Answer
First of all, this is not possible with any type of handeld GPS. You need a GPS that is able to store the position of the satellites, not only the average position on the ground.
Then, the idea is to have one or more GPS at a fixed (and if possible precisely known) location which will keep recording all the position of the satellites during the time you travel with your other hand held GPS. Those GPS are called "base stations".
When you are done, you use the information from the fix GPS to post-process your mobile GPS information (see Post processing GPS data with open source software for some softwares).
Note that the base station must be precisely located. This can be done by selecting a point of known coordinates or by taking a lot of measure. The confidence interval on your true position indeed decrease if you take a lot of measurement, but there is a temporal auto-correlation of the errors so that if you stay only a few minutes your average value is biased. Several hours is recommended.
Note that you may find base stations with open data in many parts of the world, which can be used at a few hundred km for metric accuracy.