Simone, If your are attacking this CRS stuff, could you please make a design offering an API for CRS conversions of envelopes and images.
The imagemosaic-jdbc module does also CRS conversions for the requested envelopes and returned images, but I would not swear on it. (I did my best, but I am not a CRS expert). I would be happy to use your code for these situations since you have more experience. christian Simone Giannecchini writes: > Ciao Jody, > please see below... > > ------------------------------------------------------- > Ing. Simone Giannecchini > GeoSolutions S.A.S. > Owner - Software Engineer > Via Carignoni 51 > 55041 Camaiore (LU) > Italy > > phone: +39 0584983027 > fax: +39 0584983027 > mob: +39 333 8128928 > > > http://www.geo-solutions.it > http://simboss.blogspot.com/ > http://www.linkedin.com/in/simonegiannecchini > > ------------------------------------------------------- > > > > On Fri, Apr 10, 2009 at 11:17 AM, Jody Garnett <[email protected]> wrote: >> Hi Simone: >> >>> The assumption is that I am provided with the following: >>> - bbox + crs >>> - grid-to-world transform >>> - image range (minx,miny,w,h) >> >> I do not follow why are all three are here; it appears to me that you >> could determine the image range based on the grid-to-world transform >> and the bbox+crs? > > Correct, but I am carrying around this info using a GridGeometry2D > hence I have the all 3 anyway :-). > >> >>> 2> the coverage native CRS and the request crs are NOT similar, i.e. a >>> reprojection is needed between them, and the requested envelope can be >>> reprojected to the coverage native CRS >> >> Okay. >> >>> 3> the coverage native CRS and the request crs are similar, i.e. a >>> reprojection is needed between them, and the requested envelope can >>> NOT be reprojected to the coverage native CRS (this usually happens >>> when going from project to geo or the other way around). >> >> Is this where one of the "edges" of the reprojected request envelope >> falls outside of the image; or outside of the valid area of the >> coordinate reference system? > > y > >> >>> - In the past, especially for 2 I was reprojecting the requested >>> envelope to the coverage CRS for computing the needed stuff for doing >>> a read. However this implies doing an implicit reprojection on the >>> requested grid geometry imposing that the raster range stay unchanged. >>> Therefore this may lead to a degradation of the resolution for the >>> request and to the selection of an overviews at a resolution lower >>> than needed. This is not good since in the end we need to reproject >>> again, therefore we might have raster data at a quality lower than >>> expected. >> >> I am imagining the target grid transformed into the image crs; forming >> lots of little trapezoid(or stranger) shapes. I think you could >> account for this with a little bit of math; taking the shortest >> horizontal distance / vertical distance produced by the transformed >> grid; and using that to select out the appropriate level of details. >> >>> - I am pretty sure we can merge 2 and 3 into a single case >>> - which assumption you'd expect for overviews? Many software have >>> great limitation (constant aspect ratio, constant scale factor==2, >>> etc..) and so do many important formats (jpeg2000 to mention one). >> >> I would expect to choose the overview that prevents the same source >> pixel being sampled twice for display. >> > > I am not sure I have fully understood your suggestions, however, to > clarify, what I am looking for area ideas about how to compute the > scale factor(s?) of a request for WMS/WCS in a generic way that can be > portable between different CRS. So that I can use it to select > overviews. Feedback on how people would expect us to select overviews > are welcome as well. > > Simone. > > >> Jody >> >> ------------------------------------------------------------------------------ >> This SF.net email is sponsored by: >> High Quality Requirements in a Collaborative Environment. >> Download a free trial of Rational Requirements Composer Now! >> http://p.sf.net/sfu/www-ibm-com >> _______________________________________________ >> Geotools-devel mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/geotools-devel >> > > ------------------------------------------------------------------------------ > This SF.net email is sponsored by: > High Quality Requirements in a Collaborative Environment. > Download a free trial of Rational Requirements Composer Now! > http://p.sf.net/sfu/www-ibm-com > _______________________________________________ > Geotools-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/geotools-devel ------------------------------------------------------------------------------ This SF.net email is sponsored by: High Quality Requirements in a Collaborative Environment. 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