[postgis-users] gridded data

[Pierre Racine]

Yes. This is really at the convenience of your application.

Pierre

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Stephen Crawford
Sent: Monday, May 09, 2011 12:13 PM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] gridded data

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
src176 at psu.edu
814.865.9905


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