9. The method as claimed in claim 6 wherein retrieving the location record includes: traversing the nested spatial index associated with the search term to the sub-tree of the nested spatial index; and selecting the location record in a record list in a link from the nested spatial index.
6. A method of operation of a navigation system comprising: preconstructing 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; providing a search term and a search range for searching the inverted term index; selecting with a control unit a sub-tree of the nested spatial index corresponding to the search range for restricting a search, the sub-tree for representing one or more nodes within the nested spatial index; locating the search term in the inverted term index; retrieving a location record linked to the nested spatial index and associated with the search term from within the sub-tree corresponding to the search range for displaying on a device.