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Returns one or more points interpolated along a LineString using the specified strategy.
template<typename Geometry, typename Distance, typename Pointlike, typename Strategy> void line_interpolate(Geometry const & geometry, Distance const & max_distance, Pointlike & pointlike, Strategy const & strategy)
| 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 | 
Either
            #include <boost/geometry.hpp>
          
Or
            #include <boost/geometry/algorithms/line_interpolate.hpp>
          
The function line_interpolate_point is not defined by OGC.
| ![[Note]](../../../../../../../../doc/src/images/note.png) | Note | 
|---|---|
| PostGIS contains an algorithm ST_LineInterpolatePoints with similar functionality. See the PostGIS documentation. | 
The algorithm iterates among segments of the linestring and computes interpolation points if needed.
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))