GPS drift is the difference between the actual location and the location recorded by the GPS receiver. This deviation can be up to a few meters!
If the positions are off by several meters, won't my data be too inaccurate to use for analysis?
The answer is yes and no.
The absolute accuracy of the positions is often poor, but the relative accuracy from one position to another is very good with GPS receivers like the XGPS160.
Due to a poor absolute positional accuracy, the laps do not match the track on the map very well. However, the route itself is very precise.
Since the GPS drift remains almost constant within one lap and the change over several laps is usually negligible, the positions only need to be shifted all together.
How does the correction work?
In the following screenshots you can see that the recorded data is pretty far from the actual route. This means that analyzes make little sense and the finish line and segment markers are partly ineffective.
Tap on Shift map in the top left and use the arrows to move your laps until they fit the map perfectly.