[postgis-users] Querying Multiple Rasters

[Jayson Gallardo]

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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