Comment from escada on 5 September 2015 at 20:55

A lot of traces can help one to align aerial images. They are not always aligned up with the reality. There are also places where you cannot see the path or road on the aerial images, e.g. in forests.

Maybe you can also read the answer to

Comment from Warin61 on 6 September 2015 at 01:01

A GPS trace demonstrates that there is a path there. A satellite image may no show a path - e.g. covered by trees, shadowed by buildings.

A GPS trace may demonstrate that the satellite image has offsets .. and those offsets can vary in as little as 100 meters.

However, one GPS trace is an indication, but better are many GPS traces of the same path! I have single GPS traces that are ‘out’ by some 10 meters. How do I ‘know’ that? By having many GPS traces of the same path. So if you want accuracy .. don’t rely on one GPS trace, it is better than nothing but it could have its own error.

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