[postgis-users] Re: WKT Raster project: call for fundings
tyler.erickson at mtu.edu
Wed Feb 4 20:39:18 PST 2009
Pierre Racine wrote:
>> RT_AsPolygon(RT_Intersection(fireperimeter.polygon,cover.raster)) as raster,
>> fuelbeds.shrub, fuelbeds.duff_depth, fuelbeds.overstory
> >FROM fireperimeter, cover
>> INNER JOIN fuelbeds ON cover.id=fuelbeds.id
>> WHERE RT_Intersects(fireperimeter.polygon,cover.raster);
> Actually your query would look a bit more simple:
> RT_Intersection(fireperimeter.polygon,cover.raster) as raster,
> cover.id, fuelbeds.shrub, fuelbeds.duff_depth, fuelbeds.overstory
> FROM fireperimeter, cover
> INNER JOIN fuelbeds ON cover.id=fuelbeds.id
> WHERE RT_Intersects(fireperimeter.polygon,cover.raster);
> The default behaviour of RT_Intersection() (as specified in slide 29) is to return geometries...
Based on the example shown on Slide 16, I was under the impression that
the different cover classes would be lost when performing the
RT_Intersection(geometry,raster) -> geometry operation. Specifically,
the example shows the result as two polygons that do not contain
information on the classes of the input cover raster.
It seems like RT_AsPolygon would be needed to return polygons that
represent the different classes of the input raster. I seem to be
missing something on the WKT Raster specification... could you explain
>> Given these needs, I would like to tie our contribution to the "Being
>> able to intersect vector and raster to produce vector" section of WKT
>> Raster Beta 0.1 which contains the RT_AsPolygon function and the vector
>> output forms of the RT_Intersects/RT_Intersection functions.
> Again it would be nice if you agree with Sandro about everything included in the "Being able to select RASTER values based on bbox spatial relation" section of the new schedule.
Based on the updated schedule and the description in your previous
email, it appears that the "Spatial operators with semantic matching
postgis ones" and/or "GiST indexing support" tasks are on the critical
path for development of the RT_Intersection functionality. If that is
the case, then you can assign our (MTRI's) contribution of $1200 to fund
either one of those tasks.
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