Boost C++ Libraries

Checks if the first geometry is inside or on border the second geometry.

Description

The free function covered_by checks if the first geometry is inside or on border the second geometry.

Synopsis

template<typename Geometry1, typename Geometry2>
bool covered_by(Geometry1 const & geometry1, Geometry2 const & geometry2)

Parameters

Returns

true if geometry1 is inside of or on the border of geometry2, else false

Header

Either

#include <boost/geometry.hpp>

Or

#include <boost/geometry/algorithms/covered_by.hpp>

Conformance

The function covered_by is not defined by OGC.

	Note
	Both PostGIS and Oracle contain an algorithm with the same name and the same functionality. See the PostGIS documentation.

Supported geometries

	Note
	In this status matrix above: columns are types of first parameter and rows are types of second parameter. So a point can be checked to be covered by a polygon, but not vice versa.

Complexity

Linear

See also

	Note
	The difference with the within algorithm is that this algorithm checks the border by default

Examples

Checks if the first geometry is inside or on border the second geometry

#include <iostream>

#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>

namespace bg = boost::geometry; 

int main()
{
    // Checks if the first geometry is inside or on border the second geometry.
    bg::model::polygon<bg::model::d2::point_xy<double> > poly1;
    bg::read_wkt("POLYGON((0 2,0 3,2 4,1 2,0 2))", poly1);
    bg::model::polygon<bg::model::d2::point_xy<double> > poly2;
    bg::read_wkt("POLYGON((0 4,3 4,2 2,0 1,0 4))", poly2);
    bool check_covered = bg::covered_by(poly1, poly2);
    if (check_covered) {
         std::cout << "Covered: Yes" << std::endl;
    } else {
        std::cout << "Covered: No" << std::endl;
    }

    bg::model::polygon<bg::model::d2::point_xy<double> > poly3;
    bg::read_wkt("POLYGON((-1 -1,-3 -4,-7 -7,-4 -3,-1 -1))", poly3);
    check_covered = bg::covered_by(poly1, poly3);
    if (check_covered) {
         std::cout << "Covered: Yes" << std::endl;
    } else {
        std::cout << "Covered: No" << std::endl;
    }

    // This should return true since both polygons are same, so they are lying on each other.
    check_covered = bg::covered_by(poly1, poly1);
    if (check_covered) {
         std::cout << "Covered: Yes" << std::endl;
    } else {
        std::cout << "Covered: No" << std::endl;
    }

    return 0;
}

Output:

Covered: Yes



Covered: No
Covered: Yes