1. A method of automatically constructing a graphic model of a road sign from an image to enhance a navigation database, the method comprising: receiving a plurality of images of regions about roads; identifying an image of the plurality of images that includes a road sign; performing a scale-invariant feature transform on the road sign in the image; generating a graphic model of the road sign based on results of the scale-invariant feature transform, wherein generating the graphic model includes: matching scale-invariant components determined from performing the scale-invariant feature transform with reference scale-invariant components in a data library; identifying a road sign symbol of the road sign in the image based on the matching; and retrieving a graphic road sign symbol icon from a template database based on identifying the road sign symbol; generating a local dictionary by retrieving text data of geographic features within a configurable area around a location associated with the identified image, the text data of the geographic features retrieved from the navigation database; and associating the graphic model of the road sign with the navigation database.