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GPS Data Overload

Posted by davetoo on 8 December 2008 in English.

I picked up a Garmin eTrex Vista Hcx last week, as my Zumo 550 just wasn't going to cut the mustard in areas without USGS Urban Area coverage; the tracklog sample rate is too rough. On the Vista I set the tracklog interval to 1 second; a 19-mile bicycle ride gave me a track with over 9,000 points, over 1GB in size :)

It turns out that another tool I own (ExpertGPS) does a good job of simplifying and manipulating GPX tracks, so I reduced that to 122KB and about 1,000 points. At that level I didn't feel so bad about converting it to an OSM layer (in JOSM) and uploading it. (I did clean it up a bit). Although it most cases so far I've been tracing my routes in JOSM on the USGS Urban Area map, I think this might be my new M.O.

Subject of today's mapping: Alameda Creek Trail, beginning at Coyote Hills and including at the other end a trip through Quarry Lakes Regional Rec Area in Fremont.

Location: Eberly, Fremont, Alameda County, California, 94536, United States
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Discussion

Comment from SuborbitalPigeon on 9 December 2008 at 01:05

It must be impossible for 9000 points to be a Gigabyte without each point having a lot of data logged. Are you sure it was that big?

Directly uploading GPS data as OSM data is frowned upon.

Comment from davetoo on 9 December 2008 at 02:45

Indeed, I misread the file size by three decimal places, but not the number of trackpoints. I am trying to find a compromise between laboriously hand-tracing the features on the Urban Area DOQ (which I won't have most places) and just dumping raw GPS data into the map. The high sampling rate is important for some of the complex footpaths and cycle paths I'm mapping. I may be able to split the tracks apart on either side of the very complex bits and simplify the straighter bits even more.

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