[Openstreetmap-dev] Feature extraction from GPS tracks (was: Standalone OpenStreetMap editor)

Schuyler Erle schuyler at nocat.net
Sun Apr 24 02:22:28 BST 2005


Not very well. Like I said, there's something wrong with my maths. I'd
really appreciate it if Matt or someone who knew something about it
would take a look at my code. I'm glad to give tours in person.

SDE

* On 23-Apr-2005 at  4:49PM PDT, SteveC said:
> 
> how well did the transform stuff work on the dataset living in osm?
> 
> 
> * @ 22/04/05 06:37:10 PM schuyler at nocat.net wrote:
> > * On 18-Apr-2005 at  1:11AM PDT, Nick Whitelegg said:
> > > 
> > > Does anyone have any thoughts/comments on this, given future features of the 
> > > standalone app would include overlaying Landsat and possibly other aerial 
> > > photo data? Know Java has some performance issues on large and complex apps, 
> > > but in this case, the network would appear to be the rate-determining factor.
> > 
> > I plan to build a standalone client using Python and GTk+. I already
> > have a goodly part of the code written, but that should by no means
> > stop you if you want to write one in Java. I think there ought to be a
> > multiplicity of tools available.
> > 
> > On that note, I have spent months now arsing about with methods for
> > taking track points and abstracting them into lines that might be
> > tagged as roads or walkways. All of my code is here:
> > 
> >     http://locative.us/freemap/
> > 
> > In particular, have a look at simplextract.py, which represents my
> > first attempt to apply Douglas-Peucker line simplification to a set of
> > track points. I got hung up on trying to detect and merge parallel
> > line segments. Right now I think this has the most promise.
> > 
> > I abstracted my D-P code a bit into an OGR filter that takes, say, a
> > shapefile on one end, and spits out a version generalized to some
> > tolerance. This can be found in simplify.py, but it still needs a bit
> > of debugging with the latest version of OGR.
> > 
> > Finally, have a look at hough.py, which represents my attempts to
> > apply a windowed Hough transform to a GPS track point set. It seems
> > tantalizingly close but my maths are obviously off somewhere. (Matt
> > Amos, please take note!)
> > 
> > Additionally, you will find a Python class designed for parsing GPX data
> > in gpx.py, and sample data in GPX and in shapefile (projected into UTM
> > zone 30) in that same directory.
> > 
> > In general, I have tried hard to make use of the existing Open Source
> > GIS libraries (particularly OGR and its Python bindings), as I feel
> > this is very important for us to maintain interoperability with each
> > other and especially other projects. Obviously, if we use the same
> > interchange formats (e.g. GPX, Shapefile, etc.) this isn't so
> > important, but I find that OGR offers a great deal of leverage in
> > terms of dealing with data in any format.
> > 
> > I would really appreciate feedback from anyone with an interest in the
> > subject of automating feature extraction from GPS data! I feel like my
> > code is at the 80% point and I just need some feedback from folks with
> > better experience in computational geometry than I have. I think these
> > techniques could prove quite useful.
> > 
> > SDE
> > 
> > _______________________________________________
> > Openstreetmap-dev mailing list
> > Openstreetmap-dev at vr.ucl.ac.uk
> > http://bat.vr.ucl.ac.uk/cgi-bin/mailman/listinfo/openstreetmap-dev
> > 
> 
> have fun,
> 
> SteveC steve at fractalus.com http://www.fractalus.com/steve/




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