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Tool to add back the curves from downloaded gpx files

Original Post
Ben Voytko · · Pittsburgh, PA · Joined May 2013 · Points: 2,050

So,  I can download the tracks in gpx format, but they only contain a small set of points, giving me a track which resembles a jagged line which represents the small amount of points before interpolation.

I want to apply a similar transformation to re-create the curved lines that are on the website, in a somewhat repeatable process that doesn't have me manually re-tracing each point with the spline drawing tool in QGIS. Does anyone know of a way that I can easily apply spline interpolation (or some other process) to my gps track data to reproduce (or better approximate) the curved track from MTB Project using free tools? Preferably on OSX?  

FWIW, topofusion seems to have the ability to do what I'm looking for, but I'm a mac user. So I'm looking for something that will work without Windows.

Basically, I'm trying to get my downloaded ride files to better match the actual track so my GPS doesn't keep telling me I'm off course as much.

Joseph States · · Idaho · Joined Nov 2015 · Points: 2,512

What GPS unit are you using? I personally use Garmin for everything. If you are using a Garmin, try changing in the settings, how you record your tracklog. Default will be ok for most stuff and is based on pinning points every few seconds. I find that changing it from a time interval to a distance interval will keep you from losing those switchbacks but will increase your gpx file size. Gpx files are small already so who cares if the file is double.

Garmin Colorado: Setup/Tracks/Record Method/distance/Interval/Distance in miles/000.01 (pins at 52 feet) 

Ben Voytko · · Pittsburgh, PA · Joined May 2013 · Points: 2,050

Joseph, thanks for the reply. However, I think you're misinterpreting my question.

My gps unit records detailed tracks, but if I download a track from mtb project to load on my gps to follow, it doesn't have all the curve information it has on the mtb project site ('my data' in the image above is what it looks like when I load the GPX file downloaded from mtb project on my gps). I want to add back in some the missing curve information to get a more accurate track so my gps doesn't tell me I'm off route all the time.

Also, topofusion has smoothing, but not the kind I'm looking for that makes sure the track actually passes through all the points in the gpx file. I've been looking in to the math to write a program to do this myself, but it's been a while since I've had to use applied calculus.

Guideline #1: Don't be a jerk.

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