This technical report defines the spatial representation and the map file format used in a mobile robot map-based autonomous navigation system designed to be deployed in urban areas. After a discussion about common requirements of spatial representations for map-based mobile robot autonomous navigation, a proposed environment model that fulfills previously discussed requirements is formally presented. An example of a map representing an outdoor area of an university campus of about 10000m2 is given to better illustrate the map format. Finally, the report shows simulation results on global localization and path planning using the proposed map.