NAVIGATION DEVICE HAVING NEXT VALID CHARACTER SEARCH TREE

A navigation device comprises a search tree which indicates next valid characters. The search tree has a plurality of nodes. The nodes are respectively associated with a character. At least some of the nodes respectively include a predetermined indicator to indicate that there is an alternate spelling for a character with which the respective node is associated. A processor is configured to receive a character input and to identify at least one next valid character using the search tree. The processor is configured to identify the at least one next valid character in dependence on whether the predetermined indicator in the search tree indicates that another character has an alternate spelling, the alternate spelling of the other character being the character input.