quote:Originally posted by magnetite
If you are going to compare GPS error stats from different units you will need to do the tests away from structures, trees or rock faces. An open field would be best. If you were to collect data in the forest or next to a building the variability caused by multipath (reflected) signals for a given unit could be greater than the difference in error between two units and your findings will be inconclusive. I once got to a job site and found that they had set up their GPS base station next to a buidling with a steel roof - it explained a number of problems seen in the data. It had to be moved to eliminate the problem.
@magnetite that's a very good point.
In my experiment I used my front porch as it was raining a little, and I live in ValleyCliffe, so the chief and Slhanay might be responsible for certain behaviours I've seen in my GPS units (phone, wilderness GPS and automobile GPS).
In a community project like this there's no true way to "control" for all of these factors -- the multipath being one we can influence by changing locations. Weather is another, and space weather (solar flare activity) is another. So it's not a true scientific experiment in this respect.
However, if one user takes two brands of GPS units and tests them at almost the same time and in the same location, they can compare them to each other. This is valuable to give you insight into how the units behave in the conditions where you're using them, which is the real point of the experiment, and why I thought users should log in to contribute: so they can compare their own GPS units.
If you upload a test, just note the conditions under the "description" field, and I'll be adding a feature to list just your tests.