Patent ID: 6304819
Filing Date: 2001-10-16
Classification: G01C,G09B

Abstract:
Position indicating apparatus for use with a plurality of predetermined printed map sheets, each of which is divided into a plurality of grid blocks which are referenced by a respective grid reference, the apparatus comprising:a body which is positionable over different portions of each map sheet and which is provided with a window through which a grid block of a said map sheet will be visible;position sensing means operable to receive signals from a positioning system and for generating therefrom a position indicating signal indicative of the geographical location of said body,storage means for storing data associated with said map sheets and which relates to the respective geographical areas covered by the respective map sheets of said plurality;processing means for processing said position indicating signal with said stored data for generating first output data indicative of which of said map sheets includes the geographical location indicated by said position indicating signal and indicative of the grid reference of the grid block of the indicated map sheet which contains said geographical location and second output data indicative of the position of said geographical location within the indicated grid block;output means for outputting to a user information corresponding to said first output data for enabling the user to select the indicated map sheet and to position said window of said body over said indicated grid block of said map sheet; anda movable indicator responsive to said second output data for providing within said window a visual indication of the position of said geographical location within said indicated grid block of said map sheet;wherein said position sensing means is operable to receive signals from said positioning system in terms of a wide area coordinate system, wherein said storage means in operable to store conversion data relating said wide area coordinate system to the coordinate system of the indicated map sheet and wherein said processing means is operable for generating output data using said conversion data, which output data is indicative of the grid block of the indicated map sheet and is in terms of the map coordinate system of the indicated map sheet.