not sure if this helps, but: (i) you can use points in degrees. However, your distance will be also in degree, which does not make much sense. But, for instance OpenTripPlanner uses OpenStreetMap data and just leaves the osm data in degrees. For the routing then (to get weights), it calculates distances as in (iii) below
(ii) depends on your projection. Maybe you can also use proj4j and the Google Projection (EPSG:3857) http://trac.osgeo.org/proj4j/ http://wiki.openstreetmap.org/wiki/EPSG:3857 (iii) maybe you could actually use some of the scripts, if you interested only in converting distances: http://www.movable-type.co.uk/scripts/latlong.html cheers, stefan Am 30.08.13 16:44, schrieb André Salvati: > Srs, > > just a question. As I'm dealing with GPS data, I'm getting latitude and > longitude in degrees, but as you know I can't build JTS shapes with > "degrees". So, I'm looking for an API to convert this position in meters > on the Earth's surface. > > I've tried GeoTools, but it doesn't goes well with my servers (Google > App Engine). > > Would you recommend any other? > > Thanks > > > 2013/8/26 André Fernando Salvati <[email protected] > <mailto:[email protected]>> > > > Ok Martin, > > I'm going to do some tests and share the results. > > Thank you all for your comments and ideas. > > > 2013/8/26 Martin Davis <[email protected] <mailto:[email protected]>> > > This is a very interesting question. Stefan and Michael have > provided some useful comments. Here's a little more information > about the issue, focussing on what's in JTS today, and what > could be added to improve the story. > > As you point out, there are two general approaches to this > computation: > > 1) buffer the LIneString by the query distance and compute > "contains" (or actually "containsProperly", which is a simpler > predicate) > 2) Compute the isWithinDistance predicate on the LineString > > It's hard to say which is faster *now* in JTS, and even harder > to say which is theoretically the fastest. You'll really have > to try both and see. Here's what's in JTS now: > > For #1, you should use PreparedGeometry to preprocess the buffer > polygon. My guess is that the cost of computing the initial > buffer is totally dominated by the query time. Then use the > "cointainsProperly" predicate. This will utilized indexing to > optimize the Point-In-Polygon computation. It is thread-safe now > in trunk, so you may want to build from trunk and use that code. > > For #2, the current JTS isWithinDistance is not fully optimized > for large LineStrings, since it uses a brute-force approach. > Still, if the input LineString has a fairly low number of > vertices it may still be faster than #1. As Michael pointed > out, this can be improve by indexing the LineString segments > using an STRtree and using the nearestNeighbour method to do a > fast NN query. The intention is to implement this in JTS as new > methods on the PreparedGeometry class - most of the code is > done, but it still needs to be packaged for production. > > It would be very interesting to hear which of these methods > turns out to be the fasted in your case. > > > > On Mon, Aug 26, 2013 at 10:21 AM, André Salvati > <[email protected] <mailto:[email protected]>> > wrote: > > Hi, > > I'm a beginner with JTS and this is my first post here. > > We've been working with geofences for a vehicle tracking app > and I would like to know what solution could give me a lower > CPU consumption. > > 1) Calculate and store a Buffered Area (100 meters) from a > LineString object. Run 4 million times if my vehicle > positions are inside or not that precalculated with > contains() method. > > 2) Run 4 million times isWithinDistance() method from > LineString for each position. > > Are there another options? > > Thanks. > > > ------------------------------------------------------------------------------ > Introducing Performance Central, a new site from SourceForge and > AppDynamics. Performance Central is your source for news, > insights, > analysis and resources for efficient Application Performance > Management. > Visit us today! > > http://pubads.g.doubleclick.net/gampad/clk?id=48897511&iu=/4140/ostg.clktrk > _______________________________________________ > Jts-topo-suite-user mailing list > [email protected] > <mailto:[email protected]> > https://lists.sourceforge.net/lists/listinfo/jts-topo-suite-user > > > > > ------------------------------------------------------------------------------ > Introducing Performance Central, a new site from SourceForge and > AppDynamics. Performance Central is your source for news, insights, > analysis and resources for efficient Application Performance > Management. > Visit us today! > > http://pubads.g.doubleclick.net/gampad/clk?id=48897511&iu=/4140/ostg.clktrk > _______________________________________________ > Jts-topo-suite-user mailing list > [email protected] > <mailto:[email protected]> > https://lists.sourceforge.net/lists/listinfo/jts-topo-suite-user > > > > > > ------------------------------------------------------------------------------ > Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more! > Discover the easy way to master current and previous Microsoft technologies > and advance your career. Get an incredible 1,500+ hours of step-by-step > tutorial videos with LearnDevNow. Subscribe today and save! > http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.clktrk > > > > _______________________________________________ > Jts-topo-suite-user mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/jts-topo-suite-user > ------------------------------------------------------------------------------ Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more! Discover the easy way to master current and previous Microsoft technologies and advance your career. Get an incredible 1,500+ hours of step-by-step tutorial videos with LearnDevNow. Subscribe today and save! http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.clktrk _______________________________________________ Jts-topo-suite-user mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/jts-topo-suite-user
