The paper describes the results of an urban survey using GPS together with a low cost inertial unit. The task was to map all the roads of a Portuguese city plus the location of bus stops, crossings and other urban equipment. This was accomplished using a car that was driven throughout the district carrying two GPS receivers/antennas and a low cost inertial measurement unit (IMU). All data was logged in a computer for postprocessing together with measurements from a GPS reference station. A technical description of the survey and the postprocessing software are also presented.