[postgis-users] rasters in PostGIS...

[Chapman, Martin]

Jeff,

Oracle also charges tens of thousands for that documentation. It's hard
to beat free.  Plus it's Open Source, not Open Documentation.  

On another note, it's a bad idea to store rasters in an RDMS in general.
Databases do not handle BLOB data efficiently.  A better solution is to
store your rasters on a file system and keep path information in the
database in order to access your image data.  There are numerous reasons
this is better.  Listed below are just a few:

1.  Your database will be faster and easier to manage.
2.  Your database will scale much easier.
3.  You will require less fast disk for your db.  Rasters can be stored
on tape, while your db can run on expensive fast disk.
4.  You can open images with other application like ArcMap, Erdas, that
have no knowledge of how to access raster data in a database without a
specific driver.
5.  Easier and faster to ingest rasters into your application.  If you
store rasters in a database you will have to copy all image data when
importing into the database.  This can take a long time and require a
lot of cpu power/ram/disk space.  
6.  Some databases, like SDE, actually split the image into tiles, which
means your data is rendered useless from a scientific perspective,
because once an image is clipped, you can never get the real image back,
because pixels are changed/lossed in the clipping/mosaicking process.
7.  If your database size gets too big...it may be a lengthy, if not
impossible task to back up the database.  

And the list goes on.

We have had numerous customers buy our software because their previous
solutions stored raster data in the database and it quickly became
unusable because of the time involved to ingest/process data.

The problems listed above may not specifically apply to your solution,
but I would start to think about storing files externally if I were you
because it's a better long term architecture for both large and small
GIS systems. 

Hope this helps,
Martin


-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Paul
Ramsey
Sent: Thursday, September 29, 2005 9:42 AM
To: Jeff D. Hamann; PostGIS Users Discussion
Subject: Re: [postgis-users] rasters in PostGIS...


>  I know it's a daunting task (the docs for Oracle spatial are over
> 600 pages!) but there has to be some effort otherwise PostGIS looks  
> like another "hey look what I did, isn't it cool" tool that has no  
> real staying power and application.

That's just silly, and a little insulting.

P.
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