GPSBlam is a JOSM plugin designed to exploit the availability of
multiple GPS tracks over the same straight-line path, to obtain
a handle on the location and direction of the path with optimal
accuracy. This can be useful to nail down any offsets in
existing content or imagery. - Load any GPX tracks you wish to
use, and make invisible any GPX layers you do not wish to use -
To analyse a collection of tracks made while stationary at the
same location: - left-click and hold at the point - if needed,
adjust the size of the selection circle using the scroll wheel
or arrow keys - release the mouse button - To analyse a
collection of tracks made while moving along the same straight-
line path: - left-click and hold near one end of the path - drag
to near the other end of the path - if needed, adjust the width
of the selection shape using the scroll wheel or arrow keys -
release the mouse button A new GPSBlam marker will be added to a
layer labelled GPSBlam. (Make sure it is visible.) The marker
appears in green and