[postgis-users] Raster data

[Paul Ramsey]

Chrisses:

An underlying object for raster storage exists in PostGIS now, the CHIP 
struct. However, we tuned our raster support for DEM data, to support 
our TerrainServer product. There is something to be said for storing 
everything in the database, in that mangement issues get unified behind 
SQL commands. However, as Chris points out, properly managed by *some 
kind of system* there should really not be alot of performance 
difference. I think the main advantage to DB storage would not be 
performance, it would just be the unified "do it with SQL" paradigm.

What needs to be done to bring PostGIS into the raster world? We would 
need to revisit the CHIP and think about issues around visual raster and 
data rasters, to try and support both types reasonably. We would need 
some support functions for doing common operations like mosaicking and 
pyramiding in the database. We would need a good data loader. And we 
would probably need some good thought on the "best" way to store raster 
data, in terms of schemas, attached metatdata, etc. And we would would 
need to do up a Mapserver connector so people can visualize the darn 
stuff. A WCS server would be good too.

IE, there's alot of work there. How many people are all that interested 
in raster storage?

Paul



Christoph Spoerri wrote:
> Chris,
> 
> Could you provide me with some more details on your raster setup? It sounds as 
> you have a good solution to manage such large datasets. Whats the largest 
> raster you are serving up?
> 
> Regarding the server vs. client issues: I was thinking that the 
> compression/decompression may occur on the client (save bandwidth and 
> increase performance on server). The same should be the case for 
> reprojection. Mosaicking would be done on the server. In addition the server 
> would create pyramids in order to improve the performance when rasters are 
> only used for display. 
> 
> While a db system does not have a significant advantage for small rasters (10 
> - 100 Mb?), I believe that performance improves with larger rasters, since 
> the db can index individual tiles of the entire raster and its pyramids.
> 
> In ArcSDE I'm serving up a 300 GB, seamless raster which takes between 5 - 20 
> seconds to display over the net independent of scale or extend.
> 
> Of course I'm open to any suggestions, opinions or comments.
> 
> Christoph
> 
> On Monday 10 March 2003 10:59 am, Chris G. Nicholas wrote:
> 
>>What were you looking for? We have 200+ terabytes of raster content
>>available as an OpenGIS WMS, all of which we index/manipulate using a
>>spatial db. We use transactions to store, move, etc the raster files, but
>>we certainly don't store it all *in* the db.
>>
>>For example - where do you want decompression of MrSid and/or Jpeg2000
>>imagery to occur? Where do you want reprojection to occur? How would you
>>control mosaicing? In the db or in the client?
>>
>>Chris Nicholas
>>GlobeXplorer
>>
>>-----Original Message-----
>>From:	Christoph Spoerri [mailto:spoerri at duke.edu]
>>Sent:	Mon 3/10/2003 6:51 AM
>>To:	PostGIS Users Discussion
>>Cc:
>>Subject:	[postgis-users] Raster data
>>Hi,
>>
>>I'm new to PostGIS and this list so I'm not sure if this questions came
>>already up.
>>
>>I was wondering if there are any plans on incorporating raster data into
>>PostGIS? I had some very good results with using raster data in ArcSDE and
>>would like to see a similar feature in PostGIS. Does anybody work on this?
>>Is there some need for it? If not, what are the arguments against it?
>>
>>Thanks,
>>Christoph
> 
> 
> 
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      | Refractions Research
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