Changeset 29578 in osm for applications/editors/josm/plugins

Timestamp:

2013-05-10T04:44:12+02:00 (11 years ago)

Author:

donvip

Message:

[josm_measurement] fix #josm4849 - wrong area, somewhat inaccurate length (patch by Preferred)

File:

• applications/editors/josm/plugins/measurement/src/org/openstreetmap/josm/plugins/measurement/MeasurementLayer.java (modified) (1 diff)

applications/editors/josm/plugins/measurement/src/org/openstreetmap/josm/plugins/measurement/MeasurementLayer.java

@@ -143 +143 @@
         }
     }
-
+    
+        /*
+     * Use an equal area sinusoidal projection to improve accuracy and so we can still use normal polygon area calculation
+     * http://stackoverflow.com/questions/4681737/how-to-calculate-the-area-of-a-polygon-on-the-earths-surface-using-python
+     */
     public static double calcX(LatLon p1){
-        double lat1, lon1, lat2, lon2;
-        double dlon, dlat;
-
-        lat1 = p1.lat() * Math.PI / 180.0;
-        lon1 = p1.lon() * Math.PI / 180.0;
-        lat2 = lat1;
-        lon2 = 0;
-
-        dlon = lon2 - lon1;
-        dlat = lat2 - lat1;
-
-        double a = (Math.pow(Math.sin(dlat/2), 2) + Math.cos(lat1) * Math.cos(lat2) * Math.pow(Math.sin(dlon/2), 2));
-        double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
-        return 6367000 * c;
-    }
+        return p1.lat() * Math.PI * 6367000 / 180;
+        }
 
     public static double calcY(LatLon p1){
-        double lat1, lon1, lat2, lon2;
-        double dlon, dlat;
-
-        lat1 = p1.lat() * Math.PI / 180.0;
-        lon1 = p1.lon() * Math.PI / 180.0;
-        lat2 = 0;
-        lon2 = lon1;
-
-        dlon = lon2 - lon1;
-        dlat = lat2 - lat1;
-
-        double a = (Math.pow(Math.sin(dlat/2), 2) + Math.cos(lat1) * Math.cos(lat2) * Math.pow(Math.sin(dlon/2), 2));
-        double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
-        return 6367000 * c;
+        return p1.lon() * ( Math.PI * 6367000 / 180) * Math.cos(p1.lat() * Math.PI / 180);
     }