Paul Ramsey ha scritto: > It is not uncommon to find servers either deployed using ESRI > technology, or simply following the ESRI lead, that advertise their > SRS as "EPSG:102190" or some other > 100000 "EPSG" code. ESRI in > Arc* has the concept for CRS "ids" and for "ids" in the EPSG range, > they have used the EPSG numbers. But, as Adrian has pointed out, > there are lots of useful CRS definitions that are *not* in the EPSG > database. > > (Or, that are now in the EPSG database, but did not use to be (like > 102190, the ESRI code for "BC Albers" (Cubewerx invented their own > code for it, 42102 (and then EPSG finally assigned a number, 3005 (so > now we have 3 numbers!)))). > > In order for uDig to interoperate with servers that advertise such > numbers, we need to know what those numbers mean, so we need to be > able to look them up. I can just slam them into epsg-wkt, thereby > continuing its legacy as the "pragmatic and non-standard standard > plugin". > > That will work for now. > > But, in the long term, what is the correct design way to handle > this? we have the "real" EPSG database, which will presumably be > updated over time, to include more and more projections as EPSG does > their work. And we have some projection numbers like the ESRI and > Cubewerx ones, that were pretend standards, but exist in legacy > software in lots of places. And we have the global useful ones, > which might also exist in legacy places (ESRI has a number for world > mercator, for example) which would be hand to have around. > > Any answers, projection gods? > Without being a projection expert (let alone god), the pragmatic thing would be to have EPSG as the base, and add extra things to it as we see fit, but without duplicating lots of stuff like in epsg-wkt, just by having a diff, the extra stuff that is not in EPSG. Another would be to have the extra as something we add _in_ our epsg sql script, that would allow for parameters that are sometimes needed but are not found in wkt (I kind of remember that one, but I'm not sure what's missing in wkt that we need in some transformations).
I don't know how is it working now, but can the crs authorities be linked in a chain so that we first try to decode with official wkt and then go to less official authorities up to some user defined ones? Maybe in a way that allows the user to re-order the authorities? Cheers Andrea "stating the obvious" Aime PS: I'm also wondering, did anybody try to grab the database used by proj? ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Geotools-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geotools-devel
