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Road crossing on a map (yellow) and
about half a year of tracks on it (black).
Notice the reference measure of 10 meters.
It can be seen that the accuracy of a
WAAS/EGNOS enabled GPS is about +/-3 meters
since lanes are about six meters wide.
Tracks on a straight road showing maximum
separation of about 7.4 meters yielding
+/-3.7 m for two lanes.
The square near a church has been measured by driving a car
around it. Its size is about 30 x 60 meters.