Method and apparatus for efficiently storing map data regarding calculated route for navigation system

A map data storing method for a navigation system, comprising the following steps of:

• establishing a calculated route to a destination specified by a user;
• converting data representing the calculated route to direction codes and storing the direction codes in a backup memory;
• conducting a route guidance operation to guide the user to the destination through the calculated route;
• retrieving the direction codes from the backup memory when the operation of the navigation system is turned-on again after it has been turned-off before arriving at the destination;
• establishing a remaining part of the calculated route based on the direction codes retrieved from the backup memory;
• and
• restarting the route guidance operation to guide the user to the destination through the calculated route;
• wherein the direction code includes a command code and an operand, and wherein the command code provides instruction of how to proceed to a next node, and the operant indicates a numeric value to further specify the instruction of the command code.

A map data storing apparatus for a navigation system, comprising:

• means for establishing a calculated route to a destination specified by a user;
• means for conducting a route guidance operation to guide the user to the destination through the calculated route;
• means for converting data representing the calculated route to direction codes and storing the direction codes in a backup memory when the operation of the navigation system is turned-off before reaching the destination;
• means for retrieving the direction codes from the backup memory when the operation of the navigation system is turned-on again;
• means for establishing a remaining part of the calculated route based on the direction codes retrieved from the backup memory;
• and
• means for restarting the route guidance operation to guide the user to the destination through the calculated route;
• wherein the direction includes a command code and an operand, and wherein the command code provides instruction of how to proceed to a next node, and the operant indicates a numeric value to further specify the instruction of the command code.

A map data storing apparatus for a navigation system, comprising:

• means for establishing a calculated route to a destination specified by a user;
• means for converting data representing the calculated route to direction codes and storing the direction codes in a backup memory;
• means for conducting a route guidance operation to guide the user to the destination through the calculated route;
• means for retrieving the direction codes from the backup memory when the operation of the navigation system is turned-on again after it has been turned-off before arriving at the destination;
• means for establishing a remaining part of the calculated route based on the direction codes retrieved from the backup memory;
• and
• means for restarting the route guidance operation to guide the user to the destination through the calculated route;
• wherein the direction code includes a command code and an operand, and wherein the command code provides instruction of how to proceed to a next node, and the operant indicates a numeric value to further specify the instruction of the command code.