[postgis-users] Raster Support...

[Alan]

What if you think of Rasters as a collection of points (multipoint) with an
"effect polygon" (envelope)?
For any given dataset:
	- the effect envelope size and shape is constant (just transformed
in location for each instance)
	- the spatial relationship between points is defined by the their
RowColumn index and the envelope

Kind of becomes like an image compression algorithm to my mind (but then I'm
a modeller, not an architect or programmer).

Cheers
AlanK 

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Stephen
Marshall
Sent: Saturday, 26 August 2006 6:46 AM
To: postgis-users at postgis.refractions.net
Subject: [postgis-users] Raster Support...


John,

Regarding your raster data wish:

>I would like to be able to intersect vector geometries with a range (or
>ranges) of raster values.  An example, given a DEM, what schools would
flood
>given a 2m rise in water.  Or, given a NEXRAD raster, what facility is
>getting hit by extreme rain.

I agree with the sentiment.  However, I think it could be achieved by first 
generating a polygon geometry for the area of interest (using the "filled
contouring" capability I've wished for), then using standard PostGIS 
spatial relationship functions to relate the raster-derived polygon to
other geographic features.

I think if we focus on being able to generate geometry objects from 
rasters, we can eliminate the need to implement spatial relationship
operators that work on individual pieces of rasters (e.g. pixels).  
I think this divide-and-conquer strategy would make the bounds of raster
functionality more tractable to implement, because it leverages so much
of what is already in PostGIS.  

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