So, I figured out what's going on in my particular case, and I could relatively-cleanly add a "Elevation Provider" to supply Z dimension info, and an Elevation Provider Factory to supply it, and put support for that into ReferencingFactoryFinder.
The question then becomes: Where would you want the logic for "when should GeoTools try to use this" go? Right now, GeoTools' default logic (in DefaultCoordinateOperationFactory) seems to be happy as a clam until it tries to SwapAndScaleAxis from a 2D CS to a 3D CS, and then it borks. I could special-case this particular logic, but I have to imagine the "I want to do 2D->3D" case could come up in other paths, too. Any suggestions? Thanks, Eric Thus spake Jody Garnett (jody.garn...@gmail.com): > Nice turtles all the way down reference. > I figured this out once for a change request, it has diagrams if that > helps you find your way: > > [1]http://docs.codehaus.org/display/GEOTOOLS/Improve+CRSAuthority+Concurrency+Caching+and+Connection+Use > The indirection is mostly caused by a "need for speed" - they can be > expensive to create so we cache everything we can with weak references, > but that was not good enough so we hard reference the most popular 10 or > something ... > I did not look carefully at MathTransformFactory use, I would recommend > stepping through with a debugger (a great way to figure things out when > there is this much setup and indirection involved). Note some of the other > CoordinateReferenceSystems end up being backed by their own large datasets > (Grid Shift files). I have never registered an additional MathTransform > myself, but the design does allow for it. > Jody Garnett > > On Tue, Jun 24, 2014 at 1:38 AM, Eric W. Anderson <[2]ander...@cs.cmu.edu> > wrote: > > Hi All, > > Thanks for the help. I looked at this a bit, and I'm trying to figure > out > exactly what's going on. There seems to be a nearly-endless chain of > indirection here, looking for providers of implementations of pools of > registries of sets of plugins of finders of factories of ... > > Is there somewhere -- either in the code or the documentation -- where > the > logic of "how to find or construct a transform from coordinate system A > to > coordinate system B" is located, or is it turtles all the way down? > DefaultCoordinateOperationFactory is the closest thing I've found. > > Thanks, > Eric > > Thus spake Jody Garnett ([3]jody.garn...@gmail.com): > > There is a bunch of factories for this stuff: > > > > [1][4]http://docs.geotools.org/latest/userguide/library/referencing/internal.html > > I am used to handling this as a geometry processing task in other > systems > > (rather than a math transform).... > > i.e. use either a process or a function that geometry in and a DEM > in, and > > "Drapes" the geometry over the DEM returning a new geometry. > > > - [2][5]http://docs.geotools.org/latest/userguide/tutorial/function.html > > > - [3][6]http://docs.geotools.org/latest/userguide/tutorial/process.html > > Those are worth going over anyways as they introduce how geotools > > factories work. > > -- > > Jody Garnett > > > > On Wed, Jun 18, 2014 at 4:06 AM, Eric W. Anderson > <[4][7]ander...@cs.cmu.edu> > > wrote: > > > > What would I have to do to add this? Or, put slightly > differently, > > what's the > > current process by which findMathTransform() looks for > conversions, and > > how can > > I tell it about a new one? > > > > (I know I could just hack in some code to do what I want, but > that would > > be > > ugly.) > > > > Thanks, > > Eric > > > > Thus spake Andrea Aime ([5][8]andrea.a...@geo-solutions.it): > > > On Fri, Jun 13, 2014 at 10:36 PM, Eric W. Anderson > > > <[1][6][9]ander...@cs.cmu.edu> wrote: > > > > > > Hi All, > > > > > > I'm using Geotools, and I need to convert coordinates > between 2D > > and 3D > > > coordinate reference systems. I recognize that there's no > > > universally-correct way to do this: 2D -> 3D means "making > up" a > > Z > > > coordinate, and 3D -> 2D means losing information. But, is > there > > some > > > way to teach Geotools that, in my particular context, I > want to > > use a > > > specific transformation. E.g.: > > > > > > +-----+ +-----+ > > > | | --- Z = 15 ---> | | > > > | 2D | | 3D | > > > | | <-- drop Z ---- | | > > > +-----+ +-----+ > > > I know I can transform any particular coordinate manually > this > > way, but > > > I'd like to integrate it so this Just Works. e.g. I can do > > > CRS.findMathTranform(a, b) and if a is convertible to my > 2D CRS, > > and my > > > 3D CRS is convertible to b, it works. > > > > > > No. The 3D -> 2D path is normally supported, but the 2D -> > 3D never > > is as > > > far as I remember. > > > That said, if all you want is adding an extra static > ordinate, it > > should > > > not be too hard to do it yourself. > > > I guess it could be interesting to have some tooling in > geotools > > that > > > given a 2D geometry and a helper object, would add the 3rd > > ordinate, where > > > the helper might look like: > > > interface ElevationProvider() { > > > double getElevation(DirectPosition2D pos); > > > } > > > which then the client would implement in different ways, > e.g., > > fixed > > > value, or DEM sampling. > > > As usual, it's a matter of one having enough time/funding to > > discuss the > > > evolution in the dev mailing list, > > > implement it, and merge it. > > > Cheers > > > Andrea > > > > > > -- > > > == > > > GeoServer Professional Services from the experts! Visit > > > [2][7][10]http://goo.gl/NWWaa2 for more information. > > > == > > > Ing. Andrea Aime > > > @geowolf > > > Technical Lead > > > GeoSolutions S.A.S. > > > Via Poggio alle Viti 1187 > > > 55054 Massarosa (LU) > > > Italy > > > phone: [8][11]+39 0584 962313 > > > fax: [9][12]+39 0584 1660272 > > > mob: [10][13]+39 339 8844549 > > > [3][11][14]http://www.geo-solutions.it > > > [4][12][15]http://twitter.com/geosolutions_it > > > ------------------------------------------------------- > > > > > > References > > > > > > Visible links > > > 1. mailto:[13][16]ander...@cs.cmu.edu > > > 2. [14][17]http://goo.gl/NWWaa2 > > > 3. [15][18]http://www.geo-solutions.it/ > > > 4. [16][19]http://twitter.com/geosolutions_it > > -- > > Eric W. Anderson Computer Science > Department > > [17][20]ander...@cs.cmu.edu Carnegie > Mellon > > University > > phone: [18][21]+1-412-268-1908 > Gates-Hillmann Center > > 6005 > > > > PGP key fingerprint: > > D3C5 D6FF EDED 9F1F C36D 53A3 74B7 53A6 3C74 5F12 > > > > ------------------------------------------------------------------------------ > > HPCC Systems Open Source Big Data Platform from LexisNexis Risk > > Solutions > > Find What Matters Most in Your Big Data with HPCC Systems > > Open Source. Fast. Scalable. Simple. Ideal for Dirty Data. > > Leverages Graph Analysis for Fast Processing & Easy Data > Exploration > > [19][22]http://p.sf.net/sfu/hpccsystems > > _______________________________________________ > > GeoTools-GT2-Users mailing list > > [20][23]GeoTools-GT2-Users@lists.sourceforge.net > > > [21][24]https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users > > > > References > > > > Visible links > > 1. > > [25]http://docs.geotools.org/latest/userguide/library/referencing/internal.html > > 2. > [26]http://docs.geotools.org/latest/userguide/tutorial/function.html > > 3. > [27]http://docs.geotools.org/latest/userguide/tutorial/process.html > > 4. mailto:[28]ander...@cs.cmu.edu > > 5. mailto:[29]andrea.a...@geo-solutions.it > > 6. mailto:[30]ander...@cs.cmu.edu > > 7. [31]http://goo.gl/NWWaa2 > > 8. file:///tmp/tel:%2B39%200584%20962313 > > 9. file:///tmp/tel:%2B39%200584%201660272 > > 10. file:///tmp/tel:%2B39%20%C2%A0339%208844549 > > 11. [32]http://www.geo-solutions.it/ > > 12. [33]http://twitter.com/geosolutions_it > > 13. mailto:[34]ander...@cs.cmu.edu > > 14. [35]http://goo.gl/NWWaa2 > > 15. [36]http://www.geo-solutions.it/ > > 16. [37]http://twitter.com/geosolutions_it > > 17. mailto:[38]ander...@cs.cmu.edu > > 18. file:///tmp/tel:%2B1-412-268-1908 > > 19. [39]http://p.sf.net/sfu/hpccsystems > > 20. mailto:[40]GeoTools-GT2-Users@lists.sourceforge.net > > 21. > [41]https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users > -- > Eric W. Anderson Computer Science Department > [42]ander...@cs.cmu.edu Carnegie Mellon > University > phone: [43]+1-412-268-1908 Gates-Hillmann Center > 6005 > > PGP key fingerprint: > D3C5 D6FF EDED 9F1F C36D 53A3 74B7 53A6 3C74 5F12 > > References > > Visible links > 1. > http://docs.codehaus.org/display/GEOTOOLS/Improve+CRSAuthority+Concurrency+Caching+and+Connection+Use > 2. mailto:ander...@cs.cmu.edu > 3. mailto:jody.garn...@gmail.com > 4. > http://docs.geotools.org/latest/userguide/library/referencing/internal.html > 5. http://docs.geotools.org/latest/userguide/tutorial/function.html > 6. http://docs.geotools.org/latest/userguide/tutorial/process.html > 7. mailto:ander...@cs.cmu.edu > 8. mailto:andrea.a...@geo-solutions.it > 9. mailto:ander...@cs.cmu.edu > 10. http://goo.gl/NWWaa2 > 11. file:///tmp/tel:%2B39%200584%20962313 > 12. file:///tmp/tel:%2B39%200584%201660272 > 13. file:///tmp/tel:%2B39%20%C2%A0339%208844549 > 14. http://www.geo-solutions.it/ > 15. http://twitter.com/geosolutions_it > 16. mailto:ander...@cs.cmu.edu > 17. http://goo.gl/NWWaa2 > 18. http://www.geo-solutions.it/ > 19. http://twitter.com/geosolutions_it > 20. mailto:ander...@cs.cmu.edu > 21. file:///tmp/tel:%2B1-412-268-1908 > 22. http://p.sf.net/sfu/hpccsystems > 23. mailto:GeoTools-GT2-Users@lists.sourceforge.net > 24. https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users > 25. > http://docs.geotools.org/latest/userguide/library/referencing/internal.html > 26. http://docs.geotools.org/latest/userguide/tutorial/function.html > 27. http://docs.geotools.org/latest/userguide/tutorial/process.html > 28. mailto:ander...@cs.cmu.edu > 29. mailto:andrea.a...@geo-solutions.it > 30. mailto:ander...@cs.cmu.edu > 31. http://goo.gl/NWWaa2 > 32. http://www.geo-solutions.it/ > 33. http://twitter.com/geosolutions_it > 34. mailto:ander...@cs.cmu.edu > 35. http://goo.gl/NWWaa2 > 36. http://www.geo-solutions.it/ > 37. http://twitter.com/geosolutions_it > 38. mailto:ander...@cs.cmu.edu > 39. http://p.sf.net/sfu/hpccsystems > 40. mailto:GeoTools-GT2-Users@lists.sourceforge.net > 41. https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users > 42. mailto:ander...@cs.cmu.edu > 43. file:///tmp/tel:%2B1-412-268-1908 -- Eric W. Anderson Computer Science Department ander...@cs.cmu.edu Carnegie Mellon University phone: +1-412-268-1908 Gates-Hillmann Center 6005 PGP key fingerprint: D3C5 D6FF EDED 9F1F C36D 53A3 74B7 53A6 3C74 5F12
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