1. A method of operation of a navigation system comprising: receiving an inverted term index extracted from a map data tree including a nested spatial index with nodes, wherein the map data tree represents a physical geographic region and the nodes represent a physical geographic area within the map data tree; receiving a search term and a search range for searching the inverted term index; selecting with a control unit one or more nodes within the nested spatial index corresponding to the search range; locating the search term in the inverted term index; and retrieving a location record linked to the nested spatial index and associated with the search term from within the one or more nodes corresponding to the search range for displaying on a device.
3. The method as claimed in claim 1 wherein retrieving the location record includes generating an error advisory for displaying on the device.