[postgis-users] when rasters in Postgis?

[Stephen Woodbridge]

Hi all,

Let me first preface this with:
I don't use rasters currently, but have in the past.

I think the case for managing rasters in PostGIS is more related to 
management of data and less around processing of raster, but that would 
be a logical 2nd step. Here is a simple use case.

I worked for Topozone.com and was responsible for loading 250,000+ USGS 
DOQQs, converting them to GeoTiffs, and dealing with the general data 
management. This represented about 20 TB of data that was spread out 
over 10 systems and 20 disk partitions. We organized the data into 
directories based on 1x1 degree squares. For each file we had to keep 
track of:

  * Original DOQQ name
  * DOQQ Metadata which included various attributes that we needed to 
filter on
  * where the file was stored
  * where or not it was shipped to a client
  * what shipment it was shipped on
  * etc.
  * we also had mrsid versions of the whole dataset
  * and in some cases we had resampled datasets
  * the DOQQs had to be presented via Mapserver applications
  * for any given spatial location there might be many DOQQs available 
based on mono, color, revision, other attributes
  * in addition to this there were also Topo rasters that had the same 
coverage
  * and misc. other raster data sets the had similar coverage over 
smaller regional areas.

Had I been using PostGIS at the time I might have tried to jury-rig the 
above information in the database to better help me manage the data and 
the processing tasks. I seem to remember do something with MySQL but it 
is not memorable.

While this is much larger than "most" users require the concept is the 
same. Users with raster need the ability to manage their raster in a 
ralational database and anyone could do that in theory by has storing 
all the metadata and even potentially storing the rasters a blobs. But 
the real benefit comes from being able to store the associated spatial 
extents and SRID and using PostGIS as the tileindex for mapserver and 
letting PostGIS handle the filtering of data on the layers.

I think the above is where the major benefit would come from.

As a second phase, it is not a big conceptual step to envision a set of 
PostGIS functions that are wrappers for GDAL to do some basic image 
manipulation and reprojections. This may not be well suited for the 
database as it is memory extensive and slow, but then people working 
with rasters kind of know what to expect.

So, this is an idea, it is off the top of my head without much thought 
and I realize that all ideas (dumb or otherwise) require someone to do a 
lot of work. This idea is just for discussion as the request for raster 
support has come up more than once recently.

Best regards,
   -Stephen Woodbridge

PS: Ed, if you are not on the list, I am happy to post any comments for you.

Andreas Neumann wrote:
> Hi Giorgio,
> 
> UMN mapserver is a good complement to Postgis for serving raster data. 
> It is quicker than many commercial webmap servers. If you provide 
> several resolutions for the input files (in combination with min/max 
> scales in the map files) and a spatial index (shpfile), it works very 
> efficient.
> 
> See more at:
> http://ms.gis.umn.edu/docs/howto/raster_data
> 
> Andreas
> 
> Giorgio Plazzotta wrote:
> 
>> Tx for the answer to the previous question about the geometry_column 
>> row to delete.
>> My next question is:
>> at the moment the postgis database cannot manage raster files while 
>> other commercial geodatabase engines provide this functionality.
>> how is the roadmap of Postgis? is the raster management functionality 
>> a feature we can expect in the future?
>> Giorgio
>>
>>
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> 
> 
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