[Freegis-list] Rasters, Vectors and spatial databases

[Frank Warmerdam]

On 7/29/05, Jose Gomez-Dans <jgomezdans at gmail.com> wrote:
> Hi!
> I'm working on writing some programs to analyse raster datafiles. So
> far, I have used gdal to load up the rasters. In order to carry out
> our analyses, we have downloaded from an Oracle Spatial database, the
> locations and atributes of a number of polygons, which have been
> subsequently rasterised to cover the same region and cell spacing as
> the rasters which we want to analyse. This works, and works pretty
> well. However, I would like to automatise that, because the data in
> the database changes every so often. Ideally, I would like to just
> point the program to the database and let it get the data, generate
> the vectors and carry out the pixel selection.
> 
> I'm not familiarised with the libraries that might be used to
> accomplish this. I would appreciate views on how to accomplish this
> (in its totality or even in parts!), what free sofware options are
> available, etc.

Jose, 

OGR, the vector side of GDAL/OGR can support Oracle Spatial,
so in if you build it carefully to include Oracle support you could use
OGR to extract the polygon(s) from Oracle.  Either at the commandline
with ogr2ogr, using the C++ API or perhaps from Python. 

I'm not sure what you have been using to rasterize he polygons so 
far, but I do know of folks doing this sort of thing with MapServer. 
The whole process could also be automated in GRASS which includes
GDAL raster access and OGR vector access as well as good polygon
rasterization for masking, and sophisticated sorts of raster analysis. 
You might need to be somewhat handy with shell scripting to automate
it in GRASS.

A variety of other options also exist of course.  

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent