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

SteveC steve at fractalus.com
Sun Apr 24 00:46:37 BST 2005

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.
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have fun,

SteveC steve at fractalus.com http://www.fractalus.com/steve/

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