Great info, thanks a lot.
If you think it best to store each weather variable in a separate table,
then I imagine that would be by date too, i.e. a table named
"max_temp_05_09_2011" or something like that?
Thanks,
Steve
On 5/9/2011 11:55 AM, Pierre Racine wrote:
I want to use daily weather variables that are in a grid for USA. I
would want store the daily variables ( a new grid each day) so I can
have a database that will allow the client to send a point lat/lon and
then return a calculation based on a few days worth of two or three
variables.
Do I store each day (or variable) as a new table? How does a grid get
stored in postgres? Is this a job for PostGIS Raster (though I do not
want to produce images, just queries at a point)?
Hi Steve,
PostGIS with the raster extension is just the right tool to do that. I would
recommend to store each weather variable in a separate table.
To tile (with the raster2pgsal.py -k option) or not to tile your rasters
depends on their size. Generally it is better to tile them.
Assuming your rasters are in a geographic coordinate system, you can then query
the temperature for a lat/long like this (if they are tiled):
SELECT ST_Value(rast, ST_MakePoint(lat, long) as temp
FROM yourrastertable
WHERE ST_Intersects(rast, ST_MakePoint(lat, long))
Just omit the WHERE clause if you don't tile them when loading.
Try also:
SELECT ST_Value(rast, ST_MakePoint(lat, long) as temp
FROM yourrastertable
WHERE ST_DWithin(rast, ST_MakePoint(lat, long), 0)
Which might be faster...
Please refer to the PostGIS Raster tutorials:
http://trac.osgeo.org/postgis/wiki/WKTRaster
Pierre
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Stephen Crawford
Center for Environmental Informatics
The Pennsylvania State University
[email protected]
814.865.9905
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