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As mentioned by Peter, the CRS WG is currently considering the generalized CRS concept. AFAIK the CRS group will choose one of three alternatives for how to implement the generalized CRS. It is not clear to me how this might eventually make it into ISO-land, or the real relationship between the groups. It sounded like the parametric values extension was already in ISO 19111 and my off the cuff impression isthat it's well on its way or through the process of standardization.
Those two extensions would seem to cover pressure levels and multiple time coordinates, but the specifics of how to do parameterized CRSs remains. Just looking at the CF spec as a starting point, I see about 10 horizontal reference systems including things like: -Lambert Conformal Conic -Stereographic -Azimuthal equidistant -etc I just searched for Lambert on http://www.epsg-registry.org/ and I hit upon EPSG:9802, which is Lambert Conformal. This EPSG code is referenced by other specific instances (such as EPSG:3084 "Texas Centric Lambert Conformal") codes as part of their definition. I did not search for all of the 10 mentioned in CF, but I also found EPSG:9809 for oblique stereographic. This seems to indicate that there are both specific instances as well as general types in the EPSG registry. We just need to discover how to use them properly. Aaron Ethan Davis wrote:
Hi Aaron, all, Aaron Braeckel wrote:I brought up this issue to the Coverages WG in St Louis when I co-presented with Ben. I was told that the CRS variability was resolved with parameterized CRSs via URN. I also brought up the issue of pressure levels, and it sounded like pressure levels were representable as well. I also have a note about ISO 19133 and Linear Coordinate Reference Systems, which is probably in reference to the representation of pressure levels.I'm not familiar with ISO 19133. My impression on dealing with pressure levels and such was that: 1) ISO 19111-1 "General Reference Systems" would allow for more than 3 or 4 axes, non-spatio/temporal coordinates, and multiple time coordinates. 2) And ISO 19111-2 "Extensions for Parametric values" would allow for the use of coordinates like pressure and sigma.Does anyone know about the status of these? (And if my understanding of them is correct?) Also, do they then need to be folded into GML?Thanks, Ethan
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