[gdal-dev] Layer operations, a proposal

[Frank Warmerdam]

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
>
>
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