I belive the difference between the quadtree and SRTree implementations
is that the quad tree is not editable once it is created and you start
querying it, while you can continue to add and remove envelopes from an
SRTree, intermixed between queries. Assuming that your data is static
and you don't need to change the index on the fly, I believe that the
quadtree will give you better performance.
There should be examples of how to use both of these indexes within the
geos code itself. I believe the graph-building operations use an index
to locate the nearby nodes/edges when inserting new ones? I could be
wrong, but I'm sure if you search for references to index classes within
the geos code itself, you will find a usage example.
I'll second Paul's suggestion that PostGIS will let you do this far more
easily, assuming it fits your other requirements.
Hope that helps!
Chris Hodgson
Sudipta Sarkar wrote:
Hi All,
I am trying to use GEOS to create envelope geometries for a bunch of
different tiles and create a spatial index based on these geometries.
The purpose is to select features lying within a particular tile based
on an initial query on the spatial index of these different tiles. I
am a complete newbie to GEOS so was hoping if anyone can suggest as to
which index amidst Quadtree and SRTree will work best for my purpose.
It will also be helpful if anyone can point me to any example script
in C/C++ that uses GEOS to build indexes and query them.
Any help is appreciated.
Thanks
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