[OSM-talk] relating trace points to gpx files

[Andy Robinson]

Output from my Garmin has no hdop or vdop data. I suspect this is common for
most Garmin handhelds? For NMEA output its not a problem and I do indeed
filter for accuracy before I upload to OSM

Cheers

Andy

Andy Robinson
Andy_J_Robinson at blueyonder.co.uk 

>-----Original Message-----
>From: talk-bounces at openstreetmap.org [mailto:talk-
>bounces at openstreetmap.org] On Behalf Of Joerg Ostertag
>Sent: 14 July 2006 16:30
>To: talk at openstreetmap.org
>Subject: Re: [OSM-talk] relating trace points to gpx files
>
>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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