New turf area source

app/assets/javascripts/application.js

@@ -25,7 +25,7 @@
 //= require graham_scan.min
 //= require leaflet.freedraw
 //= require smart_listing
-//= require turf
+//= require turf-area
 //= require franceconnect
 //= require bootstrap-wysihtml5
 //= require bootstrap-wysihtml5/locales/fr-FR

app/assets/javascripts/carte/carte.js

@@ -57,7 +57,7 @@ function get_external_data(latLngs) {
 
         cadastre_list = [{zoom_error: true}];
 
-        if (turf.area(polygons) < 300000)
+        if (turf_area(polygons) < 300000)
             cadastre_list = get_cadastre(latLngs);
 
         display_cadastre(cadastre_list);

vendor/assets/javascripts/turf-area.js

@@ -0,0 +1,92 @@
+var geometryArea = geometry;
+
+turf_area = function(_) {
+    if (_.type === 'FeatureCollection') {
+        for (var i = 0, sum = 0; i < _.features.length; i++) {
+            if (_.features[i].geometry) {
+                sum += geometryArea(_.features[i].geometry);
+            }
+        }
+        return sum;
+    } else if (_.type === 'Feature') {
+        return geometryArea(_.geometry);
+    } else {
+        return geometryArea(_);
+    }
+};
+
+RADIUS = 6378137;
+FLATTENING = 1/298.257223563;
+POLAR_RADIUS = 6356752.3142;
+
+ring = ringArea;
+
+function geometry(_) {
+    var area = 0, i;
+    switch (_.type) {
+        case 'Polygon':
+            return polygonArea(_.coordinates);
+        case 'MultiPolygon':
+            for (i = 0; i < _.coordinates.length; i++) {
+                area += polygonArea(_.coordinates[i]);
+            }
+            return area;
+        case 'Point':
+        case 'MultiPoint':
+        case 'LineString':
+        case 'MultiLineString':
+            return 0;
+        case 'GeometryCollection':
+            for (i = 0; i < _.geometries.length; i++) {
+                area += geometry(_.geometries[i]);
+            }
+            return area;
+    }
+}
+
+function polygonArea(coords) {
+    var area = 0;
+    if (coords && coords.length > 0) {
+        area += Math.abs(ringArea(coords[0]));
+        for (var i = 1; i < coords.length; i++) {
+            area -= Math.abs(ringArea(coords[i]));
+        }
+    }
+    return area;
+}
+
+function ringArea(coords) {
+    var p1, p2, p3, lowerIndex, middleIndex, upperIndex,
+        area = 0,
+        coordsLength = coords.length;
+
+    if (coordsLength > 2) {
+        for (i = 0; i < coordsLength; i++) {
+            if (i === coordsLength - 2) {// i = N-2
+                lowerIndex = coordsLength - 2;
+                middleIndex = coordsLength -1;
+                upperIndex = 0;
+            } else if (i === coordsLength - 1) {// i = N-1
+                lowerIndex = coordsLength - 1;
+                middleIndex = 0;
+                upperIndex = 1;
+            } else { // i = 0 to N-3
+                lowerIndex = i;
+                middleIndex = i+1;
+                upperIndex = i+2;
+            }
+            p1 = coords[lowerIndex];
+            p2 = coords[middleIndex];
+            p3 = coords[upperIndex];
+            area += ( rad(p3[0]) - rad(p1[0]) ) * Math.sin( rad(p2[1]));
+        }
+
+        area = area * RADIUS * RADIUS / 2;
+    }
+
+    return area;
+}
+
+function rad(_) {
+    return _ * Math.PI / 180;
+}