diff --git a/lib/OpenLayers/Layer/KaMap.js b/lib/OpenLayers/Layer/KaMap.js
index f030501726..9a08f3fabd 100644
--- a/lib/OpenLayers/Layer/KaMap.js
+++ b/lib/OpenLayers/Layer/KaMap.js
@@ -102,14 +102,14 @@ OpenLayers.Layer.KaMap = OpenLayers.Class(OpenLayers.Layer.Grid, {
      *
      * Parameters:
      * bounds - {<OpenLayers.Bound>}
-     * extent - {<OpenLayers.Bounds>}
+     * origin - {<OpenLayers.LonLat>}
      * resolution - {Number}
      *
      * Returns:
      * Object containing properties tilelon, tilelat, tileoffsetlat,
      * tileoffsetlat, tileoffsetx, tileoffsety
      */
-    calculateGridLayout: function(bounds, extent, resolution) {
+    calculateGridLayout: function(bounds, origin, resolution) {
         var tilelon = resolution*this.tileSize.w;
         var tilelat = resolution*this.tileSize.h;
         
diff --git a/lib/OpenLayers/Layer/MapGuide.js b/lib/OpenLayers/Layer/MapGuide.js
index de56f9d2ee..24325a1336 100644
--- a/lib/OpenLayers/Layer/MapGuide.js
+++ b/lib/OpenLayers/Layer/MapGuide.js
@@ -439,28 +439,28 @@ OpenLayers.Layer.MapGuide = OpenLayers.Class(OpenLayers.Layer.Grid, {
      *
      * Parameters:
      * bounds - {<OpenLayers.Bound>}
-     * extent - {<OpenLayers.Bounds>}
+     * origin - {<OpenLayers.LonLat>}
      * resolution - {Number}
      *
      * Returns:
      * Object containing properties tilelon, tilelat, tileoffsetlat,
      * tileoffsetlat, tileoffsetx, tileoffsety
      */
-    calculateGridLayout: function(bounds, extent, resolution) {
+    calculateGridLayout: function(bounds, origin, resolution) {
         var tilelon = resolution * this.tileSize.w;
         var tilelat = resolution * this.tileSize.h;
         
-        var offsetlon = bounds.left - extent.left;
+        var offsetlon = bounds.left - origin.lon;
         var tilecol = Math.floor(offsetlon/tilelon) - this.buffer;
         var tilecolremain = offsetlon/tilelon - tilecol;
         var tileoffsetx = -tilecolremain * this.tileSize.w;
-        var tileoffsetlon = extent.left + tilecol * tilelon;
+        var tileoffsetlon = origin.lon + tilecol * tilelon;
         
-        var offsetlat = extent.top - bounds.top + tilelat; 
+        var offsetlat = origin.lat - bounds.top + tilelat; 
         var tilerow = Math.floor(offsetlat/tilelat) - this.buffer;
         var tilerowremain = tilerow - offsetlat/tilelat;
         var tileoffsety = tilerowremain * this.tileSize.h;
-        var tileoffsetlat = extent.top - tilelat*tilerow;
+        var tileoffsetlat = origin.lat - tilelat*tilerow;
         
         return { 
           tilelon: tilelon, tilelat: tilelat,
diff --git a/lib/OpenLayers/Layer/Zoomify.js b/lib/OpenLayers/Layer/Zoomify.js
index 48272f17a7..aef827c520 100644
--- a/lib/OpenLayers/Layer/Zoomify.js
+++ b/lib/OpenLayers/Layer/Zoomify.js
@@ -258,28 +258,28 @@ OpenLayers.Layer.Zoomify = OpenLayers.Class(OpenLayers.Layer.Grid, {
      *
      * Parameters:
      * bounds - {<OpenLayers.Bound>}
-     * extent - {<OpenLayers.Bounds>}
+     * origin - {<OpenLayers.LonLat>}
      * resolution - {Number}
      *
      * Returns:
      * Object containing properties tilelon, tilelat, tileoffsetlat,
      * tileoffsetlat, tileoffsetx, tileoffsety
      */
-    calculateGridLayout: function(bounds, extent, resolution) {
+    calculateGridLayout: function(bounds, origin, resolution) {
         var tilelon = resolution * this.tileSize.w;
         var tilelat = resolution * this.tileSize.h;
 
-        var offsetlon = bounds.left - extent.left;
+        var offsetlon = bounds.left - origin.lon;
         var tilecol = Math.floor(offsetlon/tilelon) - this.buffer;
         var tilecolremain = offsetlon/tilelon - tilecol;
         var tileoffsetx = -tilecolremain * this.tileSize.w;
-        var tileoffsetlon = extent.left + tilecol * tilelon;
+        var tileoffsetlon = origin.lon + tilecol * tilelon;
 
-        var offsetlat = extent.top - bounds.top + tilelat;
+        var offsetlat = origin.lat - bounds.top + tilelat;
         var tilerow = Math.floor(offsetlat/tilelat) - this.buffer;
         var tilerowremain = tilerow - offsetlat/tilelat;
         var tileoffsety = tilerowremain * this.tileSize.h;
-        var tileoffsetlat = extent.top - tilelat*tilerow;
+        var tileoffsetlat = origin.lat - tilelat*tilerow;
 
         return {
           tilelon: tilelon, tilelat: tilelat,