Method and system for compressing data and a geographic database formed therewith and methods for use thereof in a navigation application program

A compression format for storing a collection of data on a medium, wherein said data are required to be decompressed to an uncompressed form in order to use the data for performing functions, the compression format comprising:

• an arrangement of said collection of data wherein said collection is separated into a plurality parcels each of which includes a plurality of data items which form at least part of said collection, wherein said plurality of data items in each parcel are accessed together as a group in a given sequence;
• and
• a plurality of substitution codes included among said arrangement of a plurality of data items, each of said plurality of substitution codes including an offset from a position in said arrangement of a plurality of data items at which said substitution code is located into a position sequentially backwards therefrom.

A method for decompressing a compressed data stream comprising:

• starting at a first end of the compressed data stream, advancing through a portion of the data stream until encountering a substitution code that indicates a substitution substring length and an offset backwards into said data stream toward said first end;
• and
• forming an uncompressed output from said compressed data stream, wherein said uncompressed output comprises the portion of the data stream up to said substitution code and a substitution substring appended thereto, wherein said substitution substring corresponds to that part of said portion of said substitution substring length located at said offset from said substitution code within said portion.