[postgis-users] Querying Multiple Rasters

[Jayson Gallardo]

Thanks for responding. Could you outline how I would go about doing a
partitioned table structure? My only concern with tile size is processing
time. Most of my queries will involve areas of less than 1 mi^2, and I
would clip the data into that shape. I just don't know where to start!
There's not too many resources online/print dealing with postgis rasters in
detail.


On Tue, Jul 23, 2013 at 12:57 PM, Bborie Park <dustymugs at gmail.com> wrote:

> You may not need to drop all the constraints when adding additional data
> to the table. You most likely will need to drop is the maximum extent
> constraint. Assuming the input rasters have the same scale, skew and SRID
> as that found in the table, you don't need to drop those corresponding
> constraints.
>
> If you're going to do the continental US at a fine resolution (e.g. 1
> meter), you do NOT want to put all the rasters in one table. You'll want to
> use a partitioned table structure and should consider a bigger tile size
> (depending on your hardware).
>
> -bborie
>
>
> On Tue, Jul 23, 2013 at 10:43 AM, Jayson Gallardo <jaysontrades at gmail.com>wrote:
>
>> I've looked and looked, but I have not been able to find an answer to my
>> question. I have downloaded elevation data for the state of Arkansas (in
>> the form of multiple tiles), and used raster2pgsql to upload it into a
>> single table:
>>
>> raster2pgsql -I -C -e -F -t 50x50 -l 2,4 n*/grdn* public.dem_elevation |
>> psql -U postgres -d testdb -h localhost -p 5432
>>
>> I did this because I didn't know how to pull the data if they were in
>> separate tables. Now, however I would like to add elevation data for other
>> areas. I tried to just add it to the current table, but that required
>> dropping the constraints which for such a huge amount of data seems to take
>> a long time (I let it run for 24+ hours and it didn't finish). So, my
>> question is, if I load all my rasters as individual tables, how could I run
>> something similar to this query on them all (from a python script):
>>
>> SELECT ST_AsGDALRaster(ST_CLIP(ST_Union(rast),
>> ST_GeomFromText(WKT,900913)),'GTiff') FROM "dem_elevation" WHERE
>> ST_Intersects(rast, ST_Transform(ST_GeomFromText(WKT,900913),4269))
>>
>> My goal, if it's not obvious, is to clip elevation data and export it to
>> a GTiff format and perform some operations on that raster data. Eventually,
>> I would like to put the whole continental US elevation data into my
>> database, so I need to be able to do so, while still being able to query
>> them based on an area of interest the user selects from a map. I started
>> working with PostGIS and Mapserver last month, so please forgive my
>> ignorance on such topics. Thanks in advance
>>
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>>
>
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