Wow, what a conversation I started! So here's my use case:
I have a web app that is displaying polygons and points (different layers) on a "North America" scale (although of course you can zoom in to any particular area of interest). All the data is in "Web Mercator" projection. 1) I need to allow the user to choose a location and "search by radius (in miles)" for features in one of the point or polygon layers. 2) I need to find the nearest polygon to a point (although this one is less critical, as it's a hack to get around bad data and there's a chance we can get better data). Any reprojecting I will be doing will be on the fly, as the underlying data has to remain in web mercator. Since we're talking a web app, I'm a little concerned about reprojecting a whole lot of polygons on the fly just to check distance, I'm concerned that performance will be a problem (I.E. it won't be very responsive). Some of the polygons follow county boundaries and stuff so they can have a lot of points (although I could simplify them first if it were faster). Paul, I would love to get your code for "Vicinity Distance". In the interests of full disclosure however I must admit this is paid work for a commercial customer, so I can understand if you do not wish to give me a copy of the code. Thanks, Jeff On Thu, Feb 5, 2009 at 1:08 PM, Martin Davis <[email protected]>wrote: > Another issue with ellipsoidal (geodetic) calculation is the whole date > line/poles wrapping issue. This is a major pain to deal with. I guess > local projections can be used to deal with this as well, though. > > Seems like it would be nice to have a library that would automatically > choose the best projection, do the transformation, compute the result, and > untransform... > > > > -- > Martin Davis > Senior Technical Architect > Refractions Research, Inc. > (250) 383-3022 > > _______________________________________________ > jts-devel mailing list > [email protected] > http://lists.refractions.net/mailman/listinfo/jts-devel >
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