Ticket #737: WronglyOrderedWays.diff

WronglyOrderedWays.java

@@ -59 +59 @@
         if( natural == null)
             return;
         
-        if(!natural.equals("coastline") ){
+        if(natural.equals("coastline") ){
                 errortype = "Clockwise coastline";
-        }else if(!natural.equals("water") ){
+        }else if(natural.equals("water") ){
                 errortype = "Clockwise water";
-        }else if(!natural.equals("land") ){
+        }else if(natural.equals("land") ){
                 errortype = "Clockwise land";
         } else {
                 return;
@@ -72 +72 @@
         /**
          * Test the directionality of the way
          * 
-         * Checks if the node following the northern-most node is further 
-         * west then the node previous
+         * Assuming a closed non-looping way, compute twice the area
+         * of the pollygon using the formula 2*a = sum (Xn * Yn+1 - Xn+1 * Yn)
+         * If the area is negative the way is ordered in a clockwise direction
          * 
-         * Only tests ways that the first and last node is the same currently
-         * 
          */
         
         if(w.nodes.get(0) == w.nodes.get(w.nodes.size()-1)){
-                int maxnode = -1;
-                double maxlat = -90; 
-                
-                for (int node = 0; node < w.nodes.size(); node++){
-                        double lat = w.nodes.get(node).coor.lat();
-                        if(lat > maxlat){
-                                maxnode = node;
-                                maxlat = lat;
-                        }
-                }               
-                
-                int nextnode;
-                int prevnode;
-                
-                // Determine the previous and next nodes in the loop
-                if(maxnode==0){
-                        nextnode = 1;
-                        prevnode = w.nodes.size()-1;
-                }else if(maxnode == w.nodes.size()-1){
-                        nextnode = 0;
-                        prevnode = maxnode - 1;
-                } else {
-                        nextnode = maxnode + 1;
-                        prevnode = maxnode - 1;
-                }
-                
-                double prevlon = w.nodes.get(prevnode).coor.lon();
-                double nextlon = w.nodes.get(nextnode).coor.lon();
-                
-                if(((natural.equals("coastline") || natural.equals("land")) && prevlon < nextlon) 
-                                || (natural.equals("water") && prevlon > nextlon)){             
+                double area2 = 0;
+
+                for (int node = 1; node < w.nodes.size(); node++){
+                    area2 += (w.nodes.get(node-1).coor.lon() * w.nodes.get(node).coor.lat()
+                           - w.nodes.get(node).coor.lon() * w.nodes.get(node-1).coor.lat());
+                }
+
+                if(((natural.equals("coastline") || natural.equals("land")) && area2 < 0.) 
+                                || (natural.equals("water") && area2 >  0.)){           
                         List<OsmPrimitive> primitives = new ArrayList<OsmPrimitive>();
                         primitives.add(w);
                         errors.add( new TestError(this, Severity.WARNING, tr(errortype), primitives) );