[OSM-talk] relating trace points to gpx files

Joerg Ostertag openstreetmap at ostertag.name
Fri Jul 14 16:29:46 BST 2006


On Friday 14 July 2006 16:32, Etienne wrote:
> One thing about this is that there will always be some "bad" trackpoints in
> OSM.  If you look at any city centre you'll see that the tracks can be very
> scattered.  It's quite common for a GPS to be "off" because it has picked
> up a reflected signal from a tall building.
>
> Over time, with many passes along the same street there will eventually be
> a strong _average_ scatter of the  trackpoints that will be be a good
> approximation to the actual line of a road, but many of the points will be
> quite a distance from the line and sometimes a very long distance.  Take a
> look at central London if you want to see streets with many thousands of
> trackpoints.

What about trying to add things like 
       <pdop>2.0</pdop>
       <hdop>0.9</hdop>
       <vdop>1.8</vdop>
to the trackfiles. This might give us later some more info how accurate this 
track was. And as soon as we have tracks with good reception in an area, we 
can filter for the track quality.
If your input is nmea, the current Version of osm-filtera dds these tags to 
the gpx file.
Maybe we can get similar values from other sourcefiles too.

-
Joerg




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