[OSM-talk] Strange GPS trace - drifting?

[raphael Jacquot]

Barry Crabtree wrote:
> Hi
> 
> I've been out mapping round a local residential area. Everything seemed ok
> plenty of satellites in view, but when I look at the trace it seems that
> over the space of a few minutes it has shifted what looks like about 50/100
> metres. I've put a screenshot of the trace at
> http://wiki.openstreetmap.org/index.php/Image:Grangefarm-wierd.jpg but
> haven't uploaded the gpx file because it doesn't look right!
> 
> Any thoughts on what might have happened. I've been collecting traces for a
> month & this is the first time I've seen anything like this. Have I done
> something stupid?
> 
> Cheers. Baz.

no, that's relatively classic. the satellites moved between pass1 and 
pass2...
your best bet is to handle the part to the right, and go over it another 
day for the left part.
I have that pretty pronounced in the mountains. my solution is just to 
go a couple times more, that eventually gives me better data.
of course, the real solution would be to do phase correction 
post-calculations with two gps receivers, one fixed, one moving