<div class="gmail_quote">
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Date: Mon, 22 Dec 2008 09:37:15 -0500<br>From: Kevin Webb <<a href="mailto:kfw4@cornell.edu">kfw4@cornell.edu</a>><br>
Subject: [gdal-dev] OGR and GEOS<br>To: <a href="mailto:gdal-dev@lists.osgeo.org">gdal-dev@lists.osgeo.org</a><br>Message-ID:<br> <<a href="mailto:6.2.1.2.2.20081222085228.03fe8f40@postoffice7.mail.cornell.edu">6.2.1.2.2.20081222085228.03fe8f40@postoffice7.mail.cornell.edu</a>><br>
Content-Type: text/plain; charset="us-ascii"; format=flowed<br><br>Greetings!<br><br>The documentation for the OGRGeometry class mentions the GEOS library in a<br>few of the<br>method definitions, but I wonder if there is a "stronger" OGR dependency on<br>
the GEOS<br>library than the documentation suggests. Perhaps GEOS should be a required<br>library.<br><br>I had done some processing using OGRGeometry::Intersects() without the GEOS<br>library<br>installed, I then installed GEOS to run the same tests using<br>
OGRGeometry::Distance().<br>After installing GEOS, but before running the OGRGeometry::Distance()<br>tests, I re-ran the<br>code using OGRGeometry::Intersects() and noticed different intersection<br>results.<br><br>Before-GEOS, the Intersects() method indicated intersection with 2 layer<br>
polygons. After-GEOS,<br>the Intersects() method indicated intersection with 1 layer polygon. Note:<br>After-GEOS results<br>for both Intersects() and Distance() == 0 were the same.<br><br>Should the GEOS library be a requirement for deterministic OGR processing?<br>
<br><br>Thank you.<br><br><br>KFW<br><br></blockquote>
<div>With GEOS and without GEOS you will get "deterministic" results. The difference is that the algorithm to calculate intersections without GEOS is simpler - just bounding box intersections. You want GEOS installed.</div>
<div> </div>
<div>- Ragi</div></div>