[geos-devel] no outgoing dirEdge found error

[Stuart C Sides]

Hi GEOS devels,

We are writing a C++ application which is looking for areas of overlap 
between 1000's  of polygons. The app is being
developed on Linux with g++ 4.1.0.

We first tried the stable release of GEOS 2.2.3 and received this error 
after processing several polygons:

    TopologyException: found non-noded intersection between 87.9595 
-40.3145, 87.9484 -40.2598 and 87.9857 -40.3126, 87.9575 -40.3146 87.9595 
-40.3145

While reviewing the list archives we found references to major code 
changes that might fix some of these errors, so we
upgraded to RC3 and eventually to an SVN version from 2007-09-18. We got 
through a lot more polygons without errors,
but finally received this error:

    TopologyException: no outgoing dirEdge found 87.957 -40.1615

Note: this coordinate is from the first segment of the second polygon of 
the first multi-polygon below.

In the original code, before I converted the multipolygons to strings to 
create the example, we received this error:

    TopologyException: no outgoing dirEdge found 87.7184 -40.3315

Note: this coordinate is from the first segment of the second 
multi-polygon below:

I've boiled the error down to just a few lines of code, and would 
appreciate any suggestions.  The error is thrown at the 
difference.

Thanks
Stuart



#include <string>
#include <iostream>

#include <geos/geom/PrecisionModel.h>
#include <geos/geom/GeometryFactory.h>
#include <geos/geom/Geometry.h>
#include <geos/geom/MultiPolygon.h>
#include <geos/io/WKTReader.h>

int main (int argc, char *argv[])
{
  std::string mp1s = "MULTIPOLYGON (((88.0541300495810049 
-40.3914336120775417,"
    " 88.0013586636740683 -40.3952580652168507,"
    " 87.9856522556763849 -40.3125682141688557,"
    " 88.0410955427405639 -40.3084853410231361,"
    " 88.0447770149226727 -40.3320733430391556,"
    " 88.0541300495810049 -40.3914336120775417)),"
    " ((87.9569549228361041 -40.1614847724049824,"
    " 87.9856522556763849 -40.3125682141688557,"
    " 87.9594803530699494 -40.3144955269957563,"
    " 87.9484023890450430 -40.2597855714132962,"
    " 87.9236385364479673 -40.1638760511710515,"
    " 87.9569549228361041 -40.1614847724049824)))";

  std::string mp2s = "MULTIPOLYGON (((87.7184147523609425 
-40.3314878875577705,"
    " 87.7106409229361930 -40.2916861830969211,"
    " 87.6363928113999862 -39.9074815079801084,"
    " 87.8588765594887349 -39.8933226300382628,"
    " 88.3245648150878964 -39.8616404104367064,"
    " 88.3252910982550503 -39.8653834273614933,"
    " 88.4058355104796334 -40.2774282017416283,"
    " 88.4066631207306273 -40.2815647501607259,"
    " 87.9574816223991007 -40.3146427145853394,"
    " 87.7184147523609425 -40.3314878875577705)))";

  try {
    geos::geom::PrecisionModel *model = 
        new 
geos::geom::PrecisionModel(geos::geom::PrecisionModel::FLOATING);
    geos::geom::GeometryFactory *factory = new 
geos::geom::GeometryFactory(model);

    geos::io::WKTReader *wkt = new geos::io::WKTReader();
    geos::geom::MultiPolygon *mp1 = (geos::geom::MultiPolygon 
*)wkt->read(mp1s);
    geos::geom::MultiPolygon *mp2 = (geos::geom::MultiPolygon 
*)wkt->read(mp2s);

    std::cout << "Is valid of one = " << mp1->isValid() << std::endl;
    std::cout << "Is valid of two = " << mp2->isValid() << std::endl;

    geos::geom::Geometry *diff = mp1->difference(mp2); 

    std::cout << mp1->toString() << std::endl;
    std::cout << mp2->toString() << std::endl;
    std::cout << diff->toString() << std::endl;

  }
  catch (std::exception const &se) {
    std::cout << "ERROR - " << se.what() << std::endl;
  }
  catch (...) {
    std::cout << "General error" << std::endl;
  }

}
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