[geos-devel] GEOS and Mapserver

[Steve Lime]

I've got a skeletal setup in MapServer now. Nothing functional just a
setup of how this will work. Basically I propose extending the standard
shapeObj to contain a GEOS geometry. Then I have to write the code to go
between GEOS geometries and shapeObj's. The wrappers for the GEOS
functionality then become really easy. You'll see things like
msGEOSBufferShape and so on. You'll never see the GEOS geometry and will
deal with shapeObj's. That way you can draw or use those features easily
with existing MapServer code. I also plan to make use of the PROCESSING
block as a mechanism to trigger processing. For example you might do
something like:

PROCESSING
  BUFFER 500
END

Which would trigger all features to be buffered before being released
to MapServer or MapScript. MapScript would then gain a whole bunch of
geospatial analysis methods attached to shapeObjs. That's what I'm
planning anyways. Now just to find the time to write the converters. WKT
will likely be too slow for this purpose.

Steve

Stephen Lime
Data & Applications Manager

Minnesota DNR
500 Lafayette Road
St. Paul, MN 55155
651-297-2937

>>> Godwinl at AGR.GC.CA 10/7/2004 12:29:04 PM >>>
I've cross-posted this to various lists, so I'm sorry to those who are
getting duplicates.

I'd like to beef up my Mapserver applications with some geoprocessing
functionality - buffers at present, other functions will follow.  For
now I am playing with PostGIS and having great sucess, IF my features
are all stored in the database.

What I'd like to be able to do though, is take a feature from WMS
getFeatureInfo or WFS and be able to buffer that.  As a test of this,
I
took the GML from a getFeatureInfo request and parsed it manually to
be
a WKT string.  Then used PostGIS to run the buffer.  Apart from slight
precision differences, it appeared to be close to what PostGIS would
have done with it's own feature (the WMS request was done against the
same feature through MapServer).

Now that I confirmed this is all possible, what I am missing is that
I'd
like to be able to
a.. do the conversion from GML to WKT with some script/library
b.. do this with a GML stream
c.. ultimately do this without PostGIS database dependancy.

I figure that GEOS can do the geometry format conversions, is this
right?
Has anyone written a library for linux/windows that will let me talk
to
it with PHP?

I'm prodding these lists in hopes of finding out what else is going on
out there in this area. It would be fabulous if this was all built
into
Mapserver, but from what I can tell, it's just a thought right now.

Thanks!!

Liz Godwin