1. An input data correction method for assisting a user to enter data in a navigation system, comprising the steps of: displaying a keyboard screen; inputting data through alphanumeric keys on the keyboard screen; positioning a cursor to a location of a character of the input data that is desired to be changed; searching for candidate entries that match the input data if the character at the cursor location of the input data is changed; highlighting alphanumeric keys corresponding to the characters to change the character at the cursor location so that the input data after the change match with the candidate entries; and selecting one or more highlighted keys thereby changing the input data to the candidate entry.