The method 1, wherein providing {HEAD ~ the database comprises} associating {TAIL ~ the map objects} with respective data layers, and wherein identifying the two or more matched map objects comprises searching for the two or more matched map objects only within a subset of the data layers 
The method 1 , wherein providing { HEAD ~ the database comprises } associating { TAIL ~ the map objects } with respective data layers , and wherein identifying the two or more matched map objects comprises searching for the two or more matched map objects only within a subset of the data layers
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH