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Old September 16th 16, 08:20 AM posted to sci.geo.satellite-nav
Terje Mathisen[_3_]
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Default GPX Track Editor for Android

Terje Mathisen wrote:

I wrote track reduction/optimization code a long time ago, i.e.
even before the end of Selective Availability when track points
could be up to 100 m off, but the error was random and slowly

I wrote the reduction and averaging code some 10 years ago, but I did
not use it a lot because it was not integrated with the track editing
tools I was using.

Have you implemented track adjustment tools, i.e. a way to drag
the track through points where the map tells you that it had to
pass, and the in rubber band fashion adjust all the track points
between junction/fix points?

You can force the map to pass through particular points. (Not by
dragging, though, because that doesn't work well on a touchscreen.)
There is no automatic adjustment of intermediate points, however.
What you can do is manually eliminate a series of intermediate noise
points by connecting two good points.

You should take a look at QuickRoute, a tool made by a Swedish Orienteer.

It allows you to fit arbitrarily many fix points between the map and the
track, and all other track points will be moved proportionally:


I have been doing my testing on some noisy tracks, and, although this
is inherently a tedious task, I found I was able to clean up the
garbage fairly efficiently. And, if there are multiple tracks, I've
found good results from averaging the tracks, after trimming off the
worst of the noise.

Lew Lasher

- Terje.Mathisen at
"almost all programming can be viewed as an exercise in caching"