diff --git a/src/ol/source/mapguidesource.js b/src/ol/source/mapguidesource.js
index a8ddc8484b..7c20c7468c 100644
--- a/src/ol/source/mapguidesource.js
+++ b/src/ol/source/mapguidesource.js
@@ -94,8 +94,8 @@ ol.source.MapGuide.prototype.getImage =
  * @return {number} The computed map scale.
  */
 ol.source.MapGuide.prototype.getScale = function(extent, size) {
-  var mcsW = extent[2] - extent[0];
-  var mcsH = extent[3] - extent[1];
+  var mcsW = ol.extent.getWidth(extent);
+  var mcsH = ol.extent.getHeight(extent);
   var devW = size[0];
   var devH = size[1];
   var dpi = 96;
@@ -120,6 +120,7 @@ ol.source.MapGuide.prototype.getScale = function(extent, size) {
 ol.source.MapGuide.prototype.getUrl =
     function(baseUrl, params, extent, size, projection) {
   var scale = this.getScale(extent, size);
+  var center = ol.extent.getCenter(extent);
   var baseParams = {
     'OPERATION': this.useOverlay_ ? 'GETDYNAMICMAPOVERLAYIMAGE' : 'GETMAPIMAGE',
     'VERSION': '2.0.0',
@@ -130,8 +131,8 @@ ol.source.MapGuide.prototype.getUrl =
     'SETDISPLAYWIDTH': Math.round(size[0]),
     'SETDISPLAYHEIGHT': Math.round(size[1]),
     'SETVIEWSCALE': scale,
-    'SETVIEWCENTERX': (extent[0] + extent[2]) / 2,
-    'SETVIEWCENTERY': (extent[1] + extent[3]) / 2
+    'SETVIEWCENTERX': center[0],
+    'SETVIEWCENTERY': center[1]
   };
   goog.object.extend(baseParams, params);
   return goog.uri.utils.appendParamsFromMap(baseUrl, baseParams);