Filtering points in GPX files

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  • Filtering points in GPX files
  • Premier Icon offthebrakes
    Subscriber

    I got a Satmap recently, and its great and so on. But it saves my location once per second, which causes problems when I try and upload a GPX file of my route to Tracklogs afterwards – there are simply so many points that Tracklogs runs like a dog while the file is open.

    There is a point filter feature within Tracklogs which will let me reduce the number of points to something manageable, but I have to open the full file first, so it hangs for ages until the filtering is done (i.e. at least 30 mins to filter a 40 mile route).

    Satmap's website says that if I select Advanced Power Saving mode then it will only record once per 4 seconds, which would help, but I've tried it and it doesn't appear to be true!

    Does anyone know of any freely available point filtering apps? Something that is less resource-hungry than Tracklogs? Preferably freeware 🙂 Google does not appear to be my friend on this…

    carbon
    Member

    Get a Garmin!

    Premier Icon timmys
    Subscriber

    Pretty sure GPS Babel has lots of point filtering settings, not really used it myself though.

    http://www.gpsbabel.org

    Might be able to help you here, I had the same problem as I wanted to reduce the amount of points on the snail trail for my long all-day rides – the 4 second setting does work but it still works out a lot of points. Anyway, you can do it manually by opening the file in wordpad but it's a bit labourious and you have to be careful to delete the right parts, or I was emailed a small program that will do it developed by someone on a gps forum who said I could freely distribute it, but I haven't tried it since updating my firmware so would need to test it to make sure it works ok – there were 2 versions for older firmware or newer. I could email you the software, email me (should be in profile?) and I'll try to sort it out over the weekend if you're intested? 🙂

    Digimap
    Member

    offthebrakes – The point filter in TrackLogs was originally designed for reducing points when pushing a track into a GPS route on perhaps an eTrex. The algorithm used supports visual confirmation of the track shape as the points are removed and it's good with point counts in the hundreds. The visual part is resource hungry and stifles performance when point counts are in the thousands.

    The problem, as you've already discovered, is that verbose logs from newer devices also need filtering. What we (TrackLogs) have done is to design a new filter mechanism better suited to larger tracks and this is currently implemented in the GPS transfer process (great for Garmin users!). The problem with the Satmap is that file transfer is via the regular file open of a GPX file which doesn't currently have the filter option. The positive part of all this is that this morning I've logged this into the TrackLogs bug tracker as an enhancement so we are aware of the issue which is the first phase towards getting a resolution.

    Sorry I don't have an immediate solution but hope the information helps. In the meantime the most likely 3rd party point filter would be GPS babel.

    Andy@TrackLogs

    Premier Icon offthebrakes
    Subscriber

    Not been able to log on for a few days, thanks for your help guys!

    Andy – cheers, what you says makes a lot of sense, I got the impression I wasn't using the point filter for its intended purpose. 15000 points might be a lot too many, and that was only a 4 hour ride! I'd seen the other mechanism in the Garmin GPS transfer option, but obviously I couldn't use that. However, I've checked out GPSBabel and got it to do exactly what I want, so Tracklogs is running smoothly again 🙂

    Kojaklollipop – thanks for the offer of the firmware modification, I probably don't need it now as GPSBabel has solved the problem. Curious to know how you managed to get your point recording down to once every 4 seconds though – as far as I can tell, simply switching Advanced Power Saving on should do it, but when I tried it I still got one point per second. Anything else I need to do?

    Timmys – thanks for the info, I'd seen it before but never noticed the filtering.

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