line_interpolate (with strategy)

Returns one or more points interpolated along a LineString using the specified strategy.

Synopsis

template<typename Geometry, typename Distance, typename Pointlike, typename Strategy>
void line_interpolate(Geometry const & geometry, Distance const & max_distance, Pointlike & pointlike,
                      Strategy const & strategy)

Parameters

Type	Concept	Name	Description
Geometry const &	Any type fulfilling a LineString concept	geometry	Input geometry
Distance const &	A numerical distance measure	max_distance	Distance threshold (in units depending on coordinate system) representing the spacing between the points
Pointlike &	Any type fulfilling Point or Multipoint concept	pointlike	Output: either a Point (exactly one point will be constructed) or a MultiPoint (depending on the max_distance one or more points will be constructed)
Strategy const &	A type fulfilling a LineInterpolatePointStrategy concept	strategy	line_interpolate strategy to be used for interpolation of points

Header

Either

#include <boost/geometry.hpp>

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

Conformance

The function line_interpolate_point is not defined by OGC.

	Note
	PostGIS contains an algorithm ST_LineInterpolatePoints with similar functionality. See the PostGIS documentation.

Behavior

The algorithm iterates among segments of the linestring and computes interpolation points if needed.

Available Strategies

Example

Shows how to interpolate points on a linestring in geographic coordinate system

#include <iostream>

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

using namespace boost::geometry;

int main()
{
    typedef model::d2::point_xy<double,cs::geographic<degree> > point_type;
    using segment_type = model::segment<point_type>;
    using linestring_type = model::linestring<point_type>;
    using multipoint_type = model::multi_point<point_type>;

    segment_type const s { {0, 0}, {1, 1} };
    linestring_type const l { {0, 1}, {1, 1}, {1, 2}, {0, 2}, {0, 3} };
    point_type p;
    multipoint_type mp;
    double distance = 50000;

    srs::spheroid<double> spheroid(6378137.0, 6356752.3142451793);
    strategy::line_interpolate
            ::geographic<strategy::vincenty> str(spheroid);

    std::cout << "point interpolation" << std::endl;

    line_interpolate(s, distance, p, str);
    std::cout << "on segment : " << wkt(p) << std::endl;

    line_interpolate(l, distance, p, str);
    std::cout << "on linestring : " << wkt(p) << std::endl << std::endl;

    std::cout << "multipoint interpolation" << std::endl;

    line_interpolate(s, distance, mp, str);
    std::cout << "on segment : " << wkt(mp) << std::endl;

    mp=multipoint_type();
    line_interpolate(l,distance, mp, str);
    std::cout << "on linestring : " << wkt(mp) << std::endl;

    return 0;
}

Output:

point interpolation
on segment : POINT(0.318646 0.31869)
on linestring : POINT(0.449226 1.00004)

multipoint interpolation
on segment : MULTIPOINT((0.318646 0.31869),(0.637312 0.63737),(0.956017 0.95603))
on linestring : MULTIPOINT((0.449226 1.00004),(0.898451 1.00001),(1 1.34997),
(1 1.80215),(0.74722 2.00006),(0.297791 2.00006),(0 2.15257),(0 2.60474))

Boost C++ Libraries