Method of updating a database of a navigation device and navigation device

1. A method of updating a database of a navigation device, the database storing at least a base version of a digital map for a geographical area, the method comprising:

identifying versions of the map for the geographical area which are available locally in the database or remotely from the navigation device;

executing a navigation task, including

selecting, based on the identified versions, a version of the digital map for execution of the navigation task, the selected version including data stored in a plurality of storage blocks, wherein data from a sub-set of said plurality of storage blocks is required to execute the navigation task;

selectively downloading over a wireless interface, depending on whether all storage blocks of the sub-set are already stored locally in the database, data stored in storage blocks of the sub-set which are not yet stored locally in the database, and storing the downloaded data in the database without modifying the base version of the digital map; and

using the data of the sub-set to execute the navigation task.

2. The method of claim 1 ,

wherein the data of the sub-set stored in the database is re-used when the navigation task is re-executed or when another navigation task which requires data from the sub-set is executed, until a more recent version of the digital map is identified in the identifying step.

3. The method of claim 1 ,

wherein, after the downloading and storing steps, the database includes a plurality of different versions of the digital map for a portion of the geographical area.

4. The method of claim 3 ,

wherein, when another navigation task is executed, respectively one of the plurality different versions is selected for execution of the other navigation task.

5. The method of claim 1 ,

wherein the database includes a version identifier for each of the plurality of versions of the digital map which is available locally in the database.

6. The method of claim 5 ,

wherein the selectively downloading includes storing a version identifier for the selected version in the database if no storage block of the selected version is stored in the database prior to performing the downloading step.

7. The method of claim 5 ,

wherein the base version of the digital map is selected to execute the navigation task if a version identifier for the base version indicates that the base version is as recent as or more recent than all versions of the digital map which are available remotely from the navigation device.

8. The method of claim 5 ,

wherein the database is a relational database which includes the version identifiers as attributes.

9. The method of claim 5 ,

wherein the database includes an index structure, and wherein the selectively downloading includes updating the index structure based on a version identifier for the selected version.

10. The method of claim 5 ,

wherein the database includes, for each version of the digital map which is available locally in the database, respectively a data set, and

wherein the storing includes determining, based on a comparison of a version identifier for the selected version and the version identifiers for versions which are available locally in the database, whether a new data set is to be generated for storing the downloaded data.

11. The method of claim 10 ,

wherein the downloaded data is added to a data set having a version identifier identical to the version identifier for the selected version if such a data set is already stored in the database prior to performing the downloading step.

12. The method of claim 1 , comprising:

verifying whether a data transfer via the wireless interface meets a pre-defined criterion,

wherein the base version is selected for execution of the navigation task if the data transfer fails to meet the pre-defined criterion.

13. The method of claim 1 ,

wherein execution of the navigation task is started before the downloading is completed.

14. The method of claim 13 , further comprising:

monitoring, during execution of the navigation task, whether a data transfer via the wireless interface meets at least one pre-defined criterion,

wherein the selectively downloading includes pre-fetching storage blocks based on whether the data transfer via the wireless interface meets the at least one pre-defined criterion.

15. A navigation device, comprising:

a database storing at least a base version of a digital map for a geographical area;

a processing device coupled to the database and configured to identify versions of the digital map for the geographical area which are available locally in the database or remotely from the navigation device, and to execute a navigation task, wherein the processing device is configured to

select, based on the identified versions, a version of the digital map for execution of the navigation task, the selected version including data stored in a plurality of storage blocks, wherein data from a sub-set of the plurality of storage blocks is required to execute the navigation task;

selectively download, based on whether all storage blocks of the sub-set are stored locally in the database, data stored in storage blocks of the sub-set which are not yet stored locally in the database, and store the downloaded data in the database without modifying the base version of the digital map; and

use the data of the sub-set to execute the navigation task, where the base version of the digital map remains accessible in unmodified form for use by the processing device of the navigation device.

16. The navigation device of claim 15 , further comprising:

a transceiver coupled to the processing device;

the processing device being configured to wirelessly communicate, using the transceiver, with a download center in which updated versions of the digital map are provided for downloading.