Abstract: A method and apparatus for combining two dissimilar road map databases of a given geographic region are provided. The road map database differ in degree of coverage or accuracy of coverage, or both, of the geographic region. Each database includes data defining a plurality of roads. A first set of loops is defined from roads represented in a first of the two road map databases. For each of the first set of loops, a corresponding loop is identified from roads represented in a second of the two road map databases, to define a second set of loops. Each loop of the second set of loops may include one or more links, and each link represents a portion of a road represented in the second road map database. A set of output loops corresponding to the first set of loops is generated to form an output road map database.