[R-sig-Geo] projection metadata

[Michael Sumner]

>>> I'd like to generalize this by mapping the XML tags to PROJ.4 arguments. 
>>>       
>
> If Manifold can output Well-Known Text WKT forms, in one mutation ESRI 
> WKT, then they are already read in rgdal (readOGR() reads them among 
> others). The projection code from what was spproj is now included in 
> rgdal, by the way - documentation on the websites will follow shortly.
>   

Thanks Roger - it turns out that this WKT ESRI text works for Manifold 
when it accompanies a shapefile as a .prj file. At least for one 
instance of lcc that I've tested. ;)
That makes the R to Manifold traverse very simple, for shapefiles.  I've 
yet to test .MIF, GeoTIFF etc.

Manifold will export this ESRI WKT manually in 6.50 SP1, but this is not 
yet possible programmatically. 

I've made a little bit of progress with the XML way - I can read it and 
convert it to a proj string - but it's pretty kludgy.  I'll try to clean 
up what I've done and report.
There's no clear heirarchy of how to specify datums versus coordinate 
system parameters and trying to cover the options is just very 
complicated. I can probably make a working
version that assumes WGS84 without too much trouble, with a lookup file 
for PROJ.4 names to Manifold names.

I will also request Manifold to incorporate the WKT  and PROJ.4 strings 
in the XML, at least as an option - certainly the EPSG codes as 
initials.  This seems to be about as far as the OGR xml forms go - it 
would make for a fairly simple R import and metadata assigment from 
these files.

Cheers, Mike.