[postgis-users] How do you use PostGIS Raster?

[Bborie Park]

On 06/03/2011 05:28 AM, Pierre Racine wrote:
> Hi all,
>
> I'm preparing a presentation and I need some use cases for PostGIS Raster. I would be grateful if people already using the raster side of PostGIS would describe what they already do it. Bborie, Jorge, Regina, others? These uses cases are vital for the project.
>
> On my side we are using PostGIS raster to do raster/vector analysis over large datasets. Basically determining mean values for temperature (raster), elevation (raster) for fauna observations (point buffers). Converting everything to vector and using desktop solutions proved impracticable for datasets covering the extent of Canada.
>
> For those who did not try the raster extension yet, don't be shy to express your planned experiments or your expectations.
>
> Thanks all for your contribution to the project,
>
> Pierre

Howdy all,

I use PostGIS Raster as a developer, implementer and end-user.  At my 
work, I have yet to put PostGIS Raster into production as I'm currently 
waiting on PostGIS 2.0 to be released.

At CVEC, our goal is to provide California vector control and public 
health agencies raw and computed climate, meteorological, vector 
abundance and disease risk-assessment rasters.  Some of these datasets 
are large (1km scale for every day from 1965 to today) so I wanted a 
mechanism that allowed me to easily manage the raster data, be able to 
expose the data in SQL for use by modelers and researchers, intersect 
the raster data with existing vector data and deliver on-the-fly 
generated rasters to end-users in vector control and public health.

In the past, we converted all our raster data into vectors in PostGIS 
but that became a storage and general management nightmare in addition 
to the performance hit.

Currently, I've only done minimal performance testing using one year's 
daily maximum temperature data where I wanted to aggregate the data by 
different time units, e.g. by month, half-month, disease week.  In 
addition to the storage space savings of using PostGIS raster versus 
vectors in PostGIS, a query that once took 30 - 40 seconds now completes 
in ~10 seconds.  I do need to do more testing to see if I could enhance 
performance by playing with the size of the tiles.

My development contribution the project is because there are things I'd 
like to see implemented before PostGIS 2.0 gets branched.  I'd like to 
see ST_Accum done so that I can bring the tiles for a single day 
together in one raster to be outputted to the end-user as a GDAL raster.

Pierre, is it possible to get a copy of your presentation after you've 
delivered it?  It may be nice to use in attracting more participants in 
the academic circles.  I'm currently thinking of some MRI, CT or X-Ray 
usage.

-bborie

-- 
Bborie Park
Programmer
Center for Vectorborne Diseases
UC Davis
530-752-8380
bkpark at ucdavis.edu