[postgis-users] Raster Support...

[Alan]

Paul,
Apologies for not "speaking" more exactly. 

Yep, that is exactly what I was thinking. If you have all your data in the
same "environment", and you have an extensible API for loading data to that
environment, a huge chunk of data management woes start to disappear.

Cheers
AlanK

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Paul
Ramsey
Sent: Saturday, 26 August 2006 7:27 AM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] Raster Support...


Rasters are already indexed, they are perfectly regular grids.  Any  
binary on-disk format will allow you to dereference a value or set of  
values from the raster without any searching or scanning or loading  
into memory required.

Now, raster-in-the-database would allow SQL access to the contents of  
a raster, which some developers may find handy, since it abstracts  
away the development details necessary to, for example, use the  
Python/GDAL scripting interface to read values directly out of  
rasters.  Again, as an integration environment, there are some  
positive aspects available: learn one language (SQL), get a whole  
pile of analytical and data access tools in exchange.

P.

On 25-Aug-06, at 1:28 PM, Alan wrote:

>
> Hi all,
> New guy, first post - not much PostGIS experience but a lot of  
> interest and
> a lot of Arc(insertModuleNameHere) experience.
>
> Raster is not just a format - it is, in effect, a GEOMETRY TYPE  
> that models
> "chunks" of a surface very effectively and efficiently.
>
> What's "data-basey" about it? In a word: "indexing". Why should I  
> have to
> load a 3GB file into my GDI just to query a couple of hundred pixels
> surrounding a particular vector? (If my base heights com from a DEM  
> or TIN
> or, (insert name of significant deity) forbid, a point cloud, and I  
> have
> building footprints with roof elevations I don't want to load the  
> whole
> raster to get a Building Height-Above-Ground.
>
> What if all I wanted was just to access a "value" at one particular
> location? What if I didn't want to "see" the raster, just use its  
> "data"?
>
> Also, I work in the Emergency Services / Homeland Security area and  
> pictures
> (as well as all kinds of other rasters) are a BIG TIME requirement so
> management and relationships to other features becomes critical.
>
> The other thing I've realised over the years that every vector  
> becomes a
> raster before we can see it (either on the screen or on paper).  
> Since GIS
> has (at least) two parts - Analysis & Visualisation - getting  
> control of the
> raster can only be a good thing.
>
> Cheers
> AlanK
>
>
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net
> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of  
> Paul
> Ramsey
> Sent: Saturday, 26 August 2006 6:06 AM
> To: PostGIS Users Discussion
> Subject: Re: [postgis-users] Raster Support...
>
>
> Indeed, that was exactly my intent.  To get some answers!  I
> personally have had one use-case recently, which is similar to
> Stephen Marshall's point (1), moving some vector information into
> raster space, doing some analysis which is best done in raster space,
> then pulling results back into vector space.
>
> There is nothing particularly "database"y about the use case (we
> utilize the features of the database itself hardly at all), but
> having the rasters in the database avoids an unpleasant bunch of
> scripting to dump data out to GRASS, run the analysis, stuff the
> results back in.  The database becomes an analysis integration
> environment.  There are lots of good arguments around that using a
> scripting environment like Python would be a better integration
> architecture though.
>
> I still haven't found any raster use cases that actually leverage the
> unique aspects of the database environment (high speed random access
> to tuples, transactional integrity, complex data models).
>
> Paul
>
> On 25-Aug-06, at 12:58 PM, Stephen Woodbridge wrote:
>
>> Jeff Hoffmann wrote:
>>> Paul Ramsey wrote:
>>>> To repeat:  once you get your rasters in the database, what are
>>>> you  going to do with them?
>>
>> Jeff,
>>
>> I think there are two ways to look at this statement. One is it
>> might be a dismissal, but I think the one that Paul is asking for
>> is What are your use cases, so he can collect them as you suggest.
>> It has been REALLY hard to get anyone to come forward with there
>> specific needs in this area, beside just asking for the feature.
>>
>> -Steve
>>
>>> I used to have that same question the same time anybody the topic
>>> got brought up.  I think that, if you try, you can come up with
>>> some ways raster data might be useful integrated into the database
>>> (even if it's not the best or only way of doing something).
>>> Perhaps too many people think of raster data as essentially
>>> photographic and not as a giant array of geo-referenced data
>>> points and they just dismiss it out of hand.  If you're just
>>> storing a bunch of photos in your database, I agree with the
>>> sentiment that it just makes your life difficult.  If, on the
>>> other hand, you have a DEM (for example) where the data points are
>>> elevation, you could query it to find the elevation at a point.
>>> Or take it a step further and add a Z coordinate to all that 2-D
>>> vector data in case you ever want to visualize it in 3-D.
>>> I guess the first thing I'd do if I were that interested in adding
>>> raster support is collect a bunch of possible use cases and
>>> categorize them to figure out what sort of functionality people
>>> would be interested in seeing.  I think it'd be interesting to see
>>> what people would use it for & maybe would inspire some interest
>>> in the wider community.
>>
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