diff --git a/lib/OpenLayers/Util.js b/lib/OpenLayers/Util.js
index c297b4d472..bc91db320a 100644
--- a/lib/OpenLayers/Util.js
+++ b/lib/OpenLayers/Util.js
@@ -796,13 +796,18 @@ OpenLayers.Util.rad = function(x) {return x*Math.PI/180;};
 
 /**
  * Function: distVincenty
+ * Given two objects representing points with geographic coordinates, this
+ *     calculates the distance between those points on the surface of an
+ *     ellipsoid.
  * 
  * Parameters:
  * p1 - {<OpenLayers.LonLat>} (or any object with both .lat, .lon properties)
  * p2 - {<OpenLayers.LonLat>} (or any object with both .lat, .lon properties)
  * 
  * Returns:
- * {Float}
+ * {Float} The distance (in km) between the two input points as measured on an
+ *     ellipsoid.  Note that the input point objects must be in geographic
+ *     coordinates (decimal degrees) and the return distance is in kilometers.
  */
 OpenLayers.Util.distVincenty=function(p1, p2) {
     var a = 6378137, b = 6356752.3142,  f = 1/298.257223563;