[Mapserver-users] Problem with featurequery results

[Steve Lime]

Hi Larry: That behavior is both a feature and a bug. The code considers
polygons that share an edge as intersecting and depending on you
application you might want that. It's no easy to differentiate between
polygons that overlap and those that share an edge. In the past I've
gotten around it by creating a special selection layer in which I buffer
in a tiny amount. That way the selection feature shares no coincident
edges with the features being selected.

I've not tried this but in 4.0 featurequery's respect layer TOLERANCE
values. It might be possible to set a small negative tolerance value so
that polygons would be forced to overlap a bit. If this doesn't work
then a bug should be filed so that it does work as this seems to be the
easiest way to deal with the problem.

Steve

Stephen Lime
Data & Applications Manager

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

>>> "Ellenbecker, Larry" <LEllenbecker at co.winnebago.wi.us> 08/04/03
08:59AM >>>
Hi,

I'm working on a Mapserver/CGI application using 'featurequery'.  The
application is working except that the results are not always reporting
out
correctly.  For example; I select a parcel to us as the query polygon. 
I
try to select features from a polygon layer with Certified
Survey(CSM)polygons.  My selected parcel does not have a CSM associated
with
it however there are adjacent parcels with CSM's.  The result of my
featurequery always reports the adjacent CSM's.  This phenomenon sees
to
happen whenever there are adjacent polygons in the featurequery layers.
 

I was curious if anyone else has had problems with featurequery.  In
my
application I an specifically trying to identify only line, point and
polygon features that are inside the query polygon parcel boundary.

Thanks in advance.

Larry L. Ellenbecker
GIS System Analyst
Winnebago County   
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