code: function(tolerance, resolution) {
          if(resolution !== this.resolution) {
              this.resolution = resolution;
              this.geoToleranceCache = {};
          }
          var geoTolerance = this.geoToleranceCache[tolerance];
          if(geoTolerance === undefined) {
              geoTolerance = tolerance * resolution;
              this.geoToleranceCache[tolerance] = geoTolerance;
          }
          return geoTolerance;
      }
docs: Method: getGeoTolerance
  Calculate a tolerance in map units given a tolerance in pixels.  This
  takes advantage of the <geoToleranceCache> when the map resolution
  has not changed.
  
  Parameters:
  tolerance - {Number} A tolerance value in pixels.
  resolution - {Number} Map resolution.
  
  Returns:
  {Number} A tolerance value in map units.