[postgis-users] Querying Multiple Rasters

[Bborie Park]

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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>>>>>
>>>>
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