[postgis-users] Querying Multiple Rasters

Tue Jul 23 13:14:08 PDT 2013

I'm just glad to help. Feel free to post your experience, feedback, issues
and/or wishes on the mailing-list.

-bborie

On Tue, Jul 23, 2013 at 1:10 PM, Jayson Gallardo <jaysontrades at gmail.com>wrote:

> Oh, okay. Yeah you're right about it taking time. I wrote a python script
> to generate the raster2pgsql call with the appropriate table name, so I can
> just let it run while I do other things. I really appreciate your help on
> this. I googled your name and I see you're a pretty busy person, so I'm
> glad you're taking the time to answer my questions.
>
>
> On Tue, Jul 23, 2013 at 3:05 PM, Bborie Park <dustymugs at gmail.com> wrote:
>
>> No. I'm suggesting it later as it does take time and separates
>> operations. Get everything imported first and then add constraints.
>>
>> Having said that, you can do it all at once if so desired... just
>> preference depending on volume of import data.
>>
>> -bborie
>>
>>
>> On Tue, Jul 23, 2013 at 1:02 PM, Jayson Gallardo <jaysontrades at gmail.com>wrote:
>>
>>> 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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