Buffer Query

[Steve Lime]

Only GEOS stubs have been written to date so that code's not ready. However you can do buffered queries by point and polygon by just using layer tolerance values. No buffered feature is created but distances are computed to ensure features are within a certain distance of one another. For example, to find all houses within 10 miles of a shape you'd set the tolerance for the house layer to 10 and the the tolerance units to MILES and then do the queryByShape.

Steve

>>> Peter Freimuth <pf at MAPMEDIA.DE> 12/19/2004 5:13:49 PM >>>
Abe Gillespie schrieb:

> Is there a way in PHP, or a set of steps someone could describe, to do
> a buffer query from a shape as opposed to just a point.  I'm looking
> for something that would be like this:
>
> MapObj::queryByShape(shapeObj shape, double buffer)
>
> I wouldn't mind doing this by hand if there is no built in
> functionality.  I imagine you have to loop through each line of the
> polygon and offset them by the buffer distance away from the centroid.
> Once that's done you'd have to extend all the offset lines so they
> connect.  The theory's easy, but I'm lacking in the equations to
> accomplish this.  Can anyone point me some place that will get me
> started?
>
> Thanks.
> -Abe

Dear Abe,
I'm not sure about the current status, but I know that Steve Lime was
working on the integration of the geos library which is perfect to
handle all kind of spatial queries, including buffer generation. In the
source code I recognized already some code to prepare the  using of
buffer(shapeObj) from geos. You will need a mapserver which was build
with geos support and the geos library itself.
Maybe you can contact Steve Lime to get further infos about the status
of the geos integration to mapserver.
Kind regards,
Peter

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