# Ticket #11789 (closed Bugs: fixed)

## Boost 1.59.0: geometry::intersection() asserts for spherical_equatorial coordinate system

Reported by: | Dave Stacey <drstacey@…> | Owned by: | barendgehrels |
---|---|---|---|

Milestone: | Boost 1.61.0 | Component: | geometry |

Version: | Boost 1.59.0 | Severity: | Problem |

Keywords: | Cc: |

### Description

For disjoint polygons, geometry::intersection() assert()s when used with the spherical_equatorial coordinate system. assert() comes from geometry::math::detail::normalize_spheroidal_coordinates<>::apply(), as shown by the following code:

#include <iostream> #include <deque> #include <boost/geometry.hpp> #include <boost/geometry/geometries/point_xy.hpp> #include <boost/geometry/geometries/polygon.hpp> #include <boost/geometry/geometries/adapted/c_array.hpp> #include <boost/foreach.hpp> typedef boost::geometry::cs::spherical_equatorial<boost::geometry::degree> coordinate_system; BOOST_GEOMETRY_REGISTER_C_ARRAY_CS(coordinate_system) int main() { typedef boost::geometry::model::point<double, 2, coordinate_system> point_t; typedef boost::geometry::model::polygon<point_t> polygon_t; double green_pts[][2] = { {-4.5726431789237223,52.142932977753595}, {-4.5743166242433153,52.143359442355219}, {-4.5739141406075410,52.143957260988416}, {-4.5722406991324354,52.143530796430468}, {-4.5726431789237223,52.142932977753595}}; polygon_t green; boost::geometry::append(green, green_pts); double blue_pts[][2] = { {-4.5714644516017975,52.143819810922480}, {-4.5670821923630358,52.143819810922480}, {-4.5670821923630358,52.143649055226163}, {-4.5714644516017975,52.143649055226163}, {-4.5714644516017975,52.143819810922480}}; polygon_t blue; boost::geometry::append(blue, green_pts); std::deque<polygon_t> output; // assert() comes from the following call... boost::geometry::intersection(green, blue, output); int i = 0; std::cout << "green && blue:" << std::endl; BOOST_FOREACH(polygon_t const& p, output) { std::cout << i++ << ": " << boost::geometry::area(p) << std::endl; } return 0; }

assert() is generated in the call to geometry::intersection(). Tested with both g++-4.9.3 and MSVC 2005 SP1. This is a regression on Boost 1.57.0, where the assert() is not produced.

assert() is only generated when using the cs::spherical_equatorial coordinate system; if cs::cartesian is used instead then the assert() is not generated.

Many thanks for your work on Boost and for looking at this ticket.

## Attachments

## Change History

### comment:2 Changed 15 months ago by awulkiew

This assertion fails because `expand()` function is called for Points containing very big integral coordinates. The reason is that currently, by default, floating-point coordinates are rescaled into integral coordinates internally in set operations and these integral coordinates are passed into `expand()` to calculate BoundingBoxes?. This probably also means that since these coordinates are normalized, the result is not correct.

To fix it we could disable the rescaling entirely or for non-cartesian coordinate systems, or always use cartesian `robust_point_type` in rescale policy.

To work around it, for now you could disable the rescaling by defining `BOOST_GEOMETRY_NO_ROBUSTNESS`.

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Looking at the normalize_spheroidal_coordinates<>::apply() code, I tried defining BOOST_GEOMETRY_NORMALIZE_LATITUDE, but this did not fix the assert().

I also tried calling geometry::correct() on the two polygons before calling geometry::intersection(), but likewise this had no effect and the assert() still occured.