[postgis-users] Querying Multiple Rasters

[Jayson Gallardo]

Yes, it's usgs ned. And I initially went with one table for each input
tile, but I didn't know how to join (or union) them together for my query.
On Jul 23, 2013 1:14 PM, "Bborie Park" <dustymugs at gmail.com> wrote:

> Can you describe your elevation dataset? Is it USGS NED? At which
> resolution (10 meter, 3 meter?)?
>
> As for table partitioning...
>
> http://www.postgresql.org/docs/9.0/static/ddl-partitioning.html
>
> You'll probably partition spatially, though an easy solution is to have a
> table for each input raster file.
>
> -bborie
>
>
>
>
>
> On Tue, Jul 23, 2013 at 11:05 AM, Jayson Gallardo <jaysontrades at gmail.com>wrote:
>
>> 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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