[postgis-users] raster2pgsql vs gdal2wktraster ...can someone clarify?
ackbar at ackadij.com
Mon Mar 14 08:50:00 PDT 2011
Pierre Racine-2 wrote:
>>So would you advise me to get postgis from the trunk, and compile the
>>source, or its fine to work with the version from kyngchaos for now?
> Depends if what you want to do is included or/and working fine in this
> version. The last version is always better.
>>In terms of the image - well the image pixels all have a certain value
>>associated to them (its a probability map actually, so all the values per
>>pixel are between 0->1.
> Every images have values associated with their pixels. When its not just
> RGB values, it's other values.
> I want to intersect a polygon (region) with this
>>image raster and pull out the mean probability depending on which pixels
>>were covered. The image is 3.5mb
> This is a pretty small image. You would probably not gain much tiling it
> but you can give it a try. In the first case do not add the -k option and
> in the second case add -k 25x25.
>>If I don't import -k 1x1, then what is the best way to proceed? That's how
>>the image has been produced for me to work with - there is only 1 image.
> You must understand what -k is actually doing. It will cut your raster
> into XxX tiles, one tile per row. This fasten most operation on big raster
> coverages which is not really your case. "1x1" is not a way to say you
> have only one raster...
> Be carefull here as PostGIS raster was not really intented to do this kind
> of operation on so small images. It's like using a bazooka to kill a fly.
> Many GIS packages will allow you to do this simple operation much easier
> than PostGIS...
> Why do you feel the need to use PostGIS for that?
>> Ah well I am using PostGIS already, as part of handling other vector data
>> sets etc....this raster image is just one side to it - besides, there
>> would be other images which would be bigger, and also, one has to start
>> somewhere to test whether it works. Before I stumbled upon Postgis
>> Raster, the other option was for me to transform the raster image to
>> vector data with attributes - but I want to see how well Postgis Raster
>> works for me. I need to be able to dynamically query my datasets (e.g.
>> vector data + raster images).
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