Relative GPS accuracy? GPS is not that accurate on Android devices (at least at mine) Measuring tools tell me the accuracy is between 8 and 12 Meters.

But what is about relative accuracy? When I place two marks on different coordinates in the distance of 1 meter will this distance be measurable?
Distance can be measured even if you place 2 points in one place - for mesurement used signal from satellites, and in city it's extremely difficult to predict it changes.

Accuracy depends on signal quality, and it's impossible to get it 100% even in a field, so when you move phone to 1 meter, signal change may be so small, what not detected, and it may be changed so seriously, what will displayed over 100 meters change (tested on buildings corners with HTC Desire and Nexus 7).