I was preparing some tracks for upload into openstreetmap - when I noticed that there was a huge spatter, where the n900 had been on when indoors for some time, and occasionally gone to network positioning mode.

It would be a nice feature to add 'Dilution of position' into the GPX file.

This is basically the estimated GPS error.
http://en.wikipedia.org/wiki/Dilution_of_precision_%28GPS%29

A sensible scale would probably be somewhere in the region of error in m /20.

http://www.openstreetmap.org/trace/103981/data - an example file.

The above trace - loaded into JOSM - an openstreetmap editor - http://www.mauve.plus.com/gps-err.png and zoomed into one part of the trace.
The GPS trace is shown as circles, coloured according to the speed, and with the radius equaling the approximate precision.

The large circle is - not coincidentally - when going under a bridge!
https://bugs.maemo.org/show_bug.cgi?format=multiple&id=6284 - eph is the  horizontal error in cm.

http://repository.maemo.org/pool/maemo5.0/non-free/l/location-test-gui/ shows this when logging.

In addition to displaying - it's possible with other tools to discard data with very bad HDOP.

A very useful widget - thanks!