c# - Intersection between two geographic lines -

i'm using dotspatial c# library , i'm trying use following code try find intersection point between 2 lines (i know intersect)

var geoproj = dotspatial.projections.knowncoordinatesystems.geographic.world.wgs1984;  var d1 = new featureset { projection = geoproj }; //var c1 = new coordinate(31.877484, 34.736723); //var c2 = new coordinate(31.879607, 34.732362); var c1 = new coordinate(0, -1); var c2 = new coordinate(0, 1); var line1 = new linestring(new[] { c1, c2 }); d1.addfeature(line1);  var d2 = new featureset { projection = geoproj }; //var c3 = new coordinate(31.882391, 34.73352); //var c4 = new coordinate(31.875502, 34.734851); var c3 = new coordinate(-1, 0); var c4 = new coordinate(1, 0); var line2 = new linestring(new[] { c3, c4 }); d2.addfeature(line2);  var inters = d1.intersection(d2, fieldjointype.all, null); var feats = inters.features; foreach (var feat in feats) {     console.writeline("{0}", feat.tostring()); } 

the resulting feature set empty.

what doing wrong?

i tried swap x , y components each coordinate (in case first assumed longitude instead of latitude)

thanks!

edit: per weston's comment below, i've changed coordinates of 2 lines more intersecting ones. result same.

the intersection code using limited shortcut. stuck 2 conflicting ideas. first idea featuresets have same feature type. is, if working polygon featureset, features polygons. second idea "intersection" of 2 lines line. point. featureset intersecting code designed used intersecting polygons resulting shape polygon. work points results points. in case, want find union of intersecting shapes, , throw out shapes not intersect. can accomplish taking control of features in loop ones below. have 3 examples, 1 creates point featureset intersections, , assumes intersections points, 1 keeps original d1 feature if intersects d2 feature, , unions intersecting d2 features each d1 feature. has potential of creating duplication of d2 content if d2 feature intersects more 1 d1 feature. in of these cases, may not clear attributes, since intersection officially possess attributes belong multiple d2 shapes, not one, have handled in custom way meaningful specific application.

        var geoproj = dotspatial.projections.knowncoordinatesystems.geographic.world.wgs1984;          var d1 = new featureset { projection = geoproj };         //var c1 = new coordinate(31.877484, 34.736723);         //var c2 = new coordinate(31.879607, 34.732362);         var c1 = new coordinate(0, -1);         var c2 = new coordinate(0, 1);         var line1 = new linestring(new[] { c1, c2 });         d1.addfeature(line1);           var d2 = new featureset { projection = geoproj };         //var c3 = new coordinate(31.882391, 34.73352);         //var c4 = new coordinate(31.875502, 34.734851);         var c3 = new coordinate(-1, 0);         var c4 = new coordinate(1, 0);         var line2 = new linestring(new[] { c3, c4 });         d2.addfeature(line2);           // create point featureset intersections         var result = new featureset(featuretype.point) { projection = geoproj };         foreach (ifeature feature in d1.features)         {             foreach (ifeature other in d2.features)             {                 if (feature.intersects(other))                 {                     result.addfeature(feature.intersection(other));                 }             }         }          // keep d1 lines intersect d2         result = new featureset { projection = geoproj };         foreach(ifeature feature in d1.features){             foreach(ifeature other in d2.features){                 if(feature.intersects(other)){                     result.addfeature(feature);                  }             }         }          // alternately combine intersecting lines cross         result = new featureset { projection = geoproj };         foreach (ifeature feature in d1.features)         {             ifeature union = feature;             boolean keep = false;             foreach (ifeature other in d2.features)             {                 if (feature.intersects(other))                 {                     union = union.union(other);                     keep = true;                 }             }             if (keep)             {                 result.addfeature(union);             }         }