Document that geom.getArea/Length on projected plane

src/ol/geom/linearring.js

@@ -76,7 +76,7 @@ ol.geom.LinearRing.prototype.closestPointXY =
 
 
 /**
- * @return {number} Area.
+ * @return {number} Area (on projected plane).
  * @api
  */
 ol.geom.LinearRing.prototype.getArea = function() {

src/ol/geom/linestring.js

@@ -141,7 +141,7 @@ ol.geom.LineString.prototype.getCoordinates = function() {
 
 
 /**
- * @return {number} Length.
+ * @return {number} Length (on projected plane).
  * @api
  */
 ol.geom.LineString.prototype.getLength = function() {

src/ol/geom/multipolygon.js

@@ -150,7 +150,7 @@ ol.geom.MultiPolygon.prototype.containsXY = function(x, y) {
 
 
 /**
- * @return {number} Area.
+ * @return {number} Area (on projected plane).
  * @api
  */
 ol.geom.MultiPolygon.prototype.getArea = function() {

src/ol/geom/polygon.js

@@ -140,7 +140,7 @@ ol.geom.Polygon.prototype.containsXY = function(x, y) {
 
 
 /**
- * @return {number} Area.
+ * @return {number} Area (on projected plane).
  * @api
  */
 ol.geom.Polygon.prototype.getArea = function() {