The cartographic research method basically consists of the application of maps in the description, analysis and scientific exploration of phenomena under study. Cartographic sources play a double role: they can act as a research tool or as an object -- a model of reality. This article contains topographic maps used in research of urban development with the town of Ostroleka (Poland, town area 27.94 km2) taken as an example. It presents maps of land development and cover, a map of the dynamics of changes in urbanised land and determines the main trends in town-forming forces. It also defines consecutive levels of the concentric development of the town of Ostroleka and determines the functional relationship.