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

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.