System for providing location-specific data to a user

Abstract

An FDMA/TDM satellite-based digital broadcast system is used to provide digital maps and other types of data to users at remote locations. User selection of the desired data is achieved by monitoring the TDM downlink channels of the broadcast system in accordance with a predetermined schedule or until a specific identification code is detected. The user terminals are equipped with Global Positioning System (GPS) receivers which allow the positions of the users to be determined. Based on the user positions, the user terminals are able to convert general data to location-specific data tailored to the needs of the user. The general data may comprise a digital map covering a wide geographic area, and the location-specific data may comprise a map covering a portion of the geographic region where the user is located.

What is claimed is:  
     
         1 . A system for providing location-specific data to a user, comprising: 
 a broadcast station for transmitting general data potentially usable by a plurality of users located at different geographic positions;    a relay satellite for relaying said general data from said broadcast station to said plurality of users; and    a receiver terminal provided for each of said users, said receiver terminal comprising a broadcast receiver for receiving said general data from said relay satellite, a position determination unit for determining the geographic position of the user, and a processor for converting said general data to location-specific data based on the geographic position of said user as determined by said position determination unit.    
     
     
         2 . A system as claimed in  claim 1 , wherein said position determination unit comprises a geolocation radio receiver.  
     
     
         3 . A system as claimed in  claim 1 , wherein said receiver terminal further comprises an output device for visually presenting said location-specific data to said user.  
     
     
         4 . A system as claimed in  claim 1 , wherein said general data transmitted by said broadcast station is encrypted, and wherein said receiver terminal is adapted to decrypt said data using a decryption key.  
     
     
         5 . A system as claimed in  claim 4 , wherein said receiver terminal further comprises an input device for receiving said decryption key from an external source.  
     
     
         6 . A system as claimed in  claim 8 , wherein said external source comprises a magnetically encoded card and said input device comprises a magnetic card reader.  
     
     
         7 . A system as claimed in  claim 1 , wherein said general data comprises map data for a geographic region, and wherein said location-specific data comprises map data for a portion of said geographic region where said user is located.  
     
     
         8 . A receiver terminal for providing location-specific data to a user, comprising: 
 a broadcast receiver for receiving general data transmitted by a broadcast station;    a position determination unit for determining the geographic position of the receiver terminal; and    a processor for converting said general image data to location-specific image data based on the geographic position of the receiver terminal.    
     
     
         9 . A receiver terminal as claimed in  claim 8 , wherein said position determination unit comprises a geolocation radio receiver.  
     
     
         10 . A receiver terminal as claimed in  claim 8 , wherein said receiver terminal further comprises an output device for visually presenting said location-specific data to said user.  
     
     
         11 . A receiver terminal as claimed in  claim 8 , wherein said general data transmitted by said broadcast station is encrypted, and wherein of said receiver terminal is adapted to decrypt said image data using a decryption key.  
     
     
         12 . A receiver terminal as claimed in  claim 11 , wherein said receiver terminal further comprises an input device for receiving said decryption key from an external source.  
     
     
         13 . A receiver terminal as claimed in  claim 12 , wherein said external source comprises a magnetically encoded card and said input device comprises a magnetic card reader.  
     
     
         14 . A receiver terminal as claimed in  claim 8 , wherein said general data comprises map data for a geographic region, and wherein said location-specific data comprises map data for a portion of said geographic region where said user is located.  
     
     
         15 . A method for providing location-specific data to a user, comprising: 
 transmitting general data potentially usable by a plurality of users located at different geographic positions;    receiving said general data at one of said user locations;    determining the geographic position of said user; and    converting said general data to location-specific data based on the geographic position of said user.    
     
     
         16 . A method as claimed in  claim 15 , further comprising the step of relaying said transmitted general data through a satellite.  
     
     
         17 . A method as claimed in  claim 15 , wherein the step of determining the geographic position of said user comprises receiving geolocation radio signals.  
     
     
         18 . A method as claimed in  claim 15 , further comprising the step of displaying said location-specific data to said user.  
     
     
         19 . A method as claimed in  claim 15 , wherein said transmitted general data is encrypted, and wherein said method further comprises the step of decrypting said image data at said user location.  
     
     
         20 . A method as claimed in  claim 15 , wherein said general data comprises map data for a geographic region, and wherein said location-specific data comprises map data for a portion of said geographic region where said user is located.