[OSM-dev] Sanity check please - ignore GPS-point duplicates intrack data

Andy Robinson Andy_J_Robinson at blueyonder.co.uk
Fri Jun 15 09:32:52 BST 2007


michael_j at email.de wrote:
>Sent: 14 June 2007 11:31 PM
>To: dev at openstreetmap.org
>Subject: [OSM-dev] Sanity check please - ignore GPS-point duplicates
>intrack data
>
>Hi,
>
>last week I have uploaded to OSM many gpx-files generated by my GPS-
>receiver. After uploading I noticed, that my GPS-receiver had been in
>Sports mode instead of Navigation mode and thus took GPS-points maybe 20
>times  more often. This resulted in huge GPX-files.
>
>As a result now downloading the uploaded GPS-points with Josm of other than
>tiny areas  becomes impossible.I have seen areas with only few GPS-tracks
>taken, however containing about 1 GPS-point per 20 square meters of the
>displayed area.
>
>Today I downloaded the bounding box
>(8.284247155697123,51.675814750870174,8.344998008366737,51.727143022309406)
>which is about 20 km x 20 km = 40 000 000 square meter. Until now Josm had
>downloaded about 1.500 000 GPS-points corresponding (380-http pages) and is
>still not finished.
>
>Here is the URL:
>http://www.openstreetmap.org/api/0.4/trackpoints?bbox=8.284247155697123,51.
>675814750870174,8.344998008366737,51.727143022309406&page=0
>
>When now looking at this track data it appears that very many GPS-points
>are identical with their predecessor. As no time information is provided -
>their information content has zero value.
>
snip

There is also a method of ensuring that the original GPX file you upload to
OSM is not over bloated with duplicate point data. I had this problem
originally with my PDA which spits out two different NMEA sentences with the
same location data in sequence. I fixed this problem by using gpsbabel with
the track "merge" function enabled. I do this on the GPX file rather than on
the original NMEA sentences file as for some reason that appears for me to
be more reliable. Works a treat.

Cheers,

Andy

Andy Robinson
andy_j_robinson at blueyonder.co.uk






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