Hey Michael,
All the code I'm currently writing is for inclusion in the PostGIS
Raster project.
Specialized C programs running against flat files will almost always be
faster than PostGIS Raster. But, if PostGIS Raster can return an answer
in a reasonable time frame (<= 10 seconds ideally), my users will be happy.
Currently, my testing of a polygon filter against a daily coverage
limited by a half month takes ~30 seconds. But, this is because of the
inefficiencies in ST_Intersection.
If you have any glaring performance inefficiencies, please do let us
know so that we see if some work could be done to speed things up.
-bborie
On 08/25/2011 04:46 PM, Michael Akinde wrote:
Hi,
Sounds interesting. Is your code online anywhere?
All of our source code is GPL and available at https://github.com/wdb. WDB is the
backend database server for yr.no, Norway's largest weather site with ~3M visitors
a week. It's heavily optimized for point retrieval from grids - which it does very
effectively (an average yr.no weather page retrieves approximately 3000 points
in<0.2s). We also recently implemented a NetCDF-Java interface to the database,
to facilitate easy link up with WMS services (at least in theory).
Our plan now is to extend and optimize the functionality for polygon retrieval
and point data, since the system is getting leveraged for a variety of
different types of projects.
I don't think we'll be moving our data into PostGIS rasters (our experiments so
far haven't shown any encouraging results performance-wise - perhaps not
surprising, given that our current algorithms is essentially C code working on
flat-files); but I hope that we can leverage the algorithms discussed in the
thread to do the geo-spatial calculations for the more nasty queries using
PostGIS. Pierre was kind enough to demonstrate that it can be done fairly
easily - now I just have to figure out how to do it efficiently enough that our
users will be happy.
st_intersect(raster, raster) sounds very interesting, but what would be the
result from the function?
Regards,
Michael A.
--
Bborie Park
Programmer
Center for Vectorborne Diseases
UC Davis
530-752-8380
[email protected]
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