docs: 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;
      }