[postgis-users] Querying Multiple Rasters

Tue Jul 23 13:02:53 PDT 2013

Okay, is there a specific reason why? As your link states: "raster2pgsql loader
uses this function to register raster tables". Are you saying I should
specify constraints that will be similar across all tables?

On Tue, Jul 23, 2013 at 2:53 PM, Bborie Park <dustymugs at gmail.com> wrote:

> I'd suggest adding constraints after the fact through SQL instead of
> letting raster2pgsql do it.
>
> http://www.postgis.net/docs/manual-2.0/RT_AddRasterConstraints.html
>
> -bborie
>
>
> On Tue, Jul 23, 2013 at 12:51 PM, Jayson Gallardo <jaysontrades at gmail.com>wrote:
>
>> So based on the link you provided, and what else I've gathered, I first
>> create a parent table:
>> CREATE TABLE dem_elevation
>> (
>>   rid integer NOT NULL PRIMARY KEY
>>   rast raster,
>>
>> );
>>  Then I run raster2pgsql on all the downloaded elevation data, sending
>> each input tile to its own table, ie. dem_elevation_n36w091. Then alter
>> table to inherit from parent:
>> ALTER TABLE dem_elevation_n36w091 INHERIT dem_elevation;
>>
>> With raster2pgsql taking care of setting the constraints for each table.
>> Now, I can just query the parent table dem_elevation to get what I need?
>>
>>
>> On Tue, Jul 23, 2013 at 2:33 PM, Bborie Park <dustymugs at gmail.com> wrote:
>>
>>> I use the USGS NED 10 meter for California with one table for each input
>>> raster. In the partitioned table scheme, data tables inherit from a
>>> template (parent) table. Queries run on the parent table access the
>>> inherited tables.
>>>
>>> -bborie
>>>
>>>
>>> On Tue, Jul 23, 2013 at 11:56 AM, Jayson Gallardo <
>>> jaysontrades at gmail.com> wrote:
>>>
>>>> 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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