[gdal-dev] Layer operations, a proposal

[Jason Roberts]

As I have mentioned previously
(http://lists.osgeo.org/pipermail/gdal-dev/2010-January/023089.html) I think
something like this would be a great addition to OGR. No doubt it would be a
huge job--basically turning OGR into a GIS--but if it could be done well,
with sufficient performance and in the core API, then many systems could
potentially leverage it, instead of everybody implementing their own
versions of Ari's pseudocode.

Best,
Jason

-----Original Message-----
From: gdal-dev-bounces at lists.osgeo.org
[mailto:gdal-dev-bounces at lists.osgeo.org] On Behalf Of Frank Warmerdam
Sent: Tuesday, April 17, 2012 7:32 PM
To: Ari Jolma
Cc: gdal-dev at lists.osgeo.org
Subject: Re: [gdal-dev] Layer operations, a proposal

Ari,

I think this would be an interesting addition.   Would you be willing
to write up an RFC?

I think the layer creation step should be a different call than the feature
processing step to maximize the chance that folks who need to do something
very format specific at layer creation can do so and still use the generic
algorithm for processing the features.

Your operations appear to be focused on spatial relationships, but I've also
heard a lot of interest in feature joins on attribute fields.  One case is
just merging features from a layer with a common attribute value.  Another
case would be some sort of attribute based join between layers.  Hopefully
we can use a reasonably similar approach for a variety of operations.

I'm curious how you plan to handle the spatial relationships efficiently?
An in memory spatial index?  I'd like have the API overly constrain how we
implement this as I can imagine the internal operation implementation
evolving over time, and perhaps taking different strategies for different
styles of input data.  For instance an in-memory spatial index might not
make much sense for large numbers of very simple point features while it
would be good for heavy polygon features.


Best regards,
Frank

On Tue, Apr 17, 2012 at 2:42 PM, Ari Jolma <ari.jolma at gmail.com> wrote:
> Folks,
>
> I propose a set of new methods for OGR layers (see the PDF). I took 
> the basic ideas from page 
> http://courses.washington.edu/gis250/lessons/Model_Builder/ which 
> seems rather comprehensive. I wrote the pseudo code myself quickly 
> (thus it may not be optimal and may contain bugs - improvement 
> suggestions are of course welcome).
>
> I was considering to write these in Perl (on top of the Perl bindings) 
> but probably they could also be in OGR core. Code-wise they would 
> probably go into ogrlayer.cpp.
>
> If there is support/interest, I assume I should submit this as a RFC 
> (with a patch)?
>
> Best regards,
>
> Ari
>
>
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/gdal-dev



-- 
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I set the clouds in motion - turn up   | Frank Warmerdam,
warmerdam at pobox.com light and sound - activate the windows |
http://pobox.com/~warmerdam and watch the world go round - Rush    |
Geospatial Software Developer
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