This set of maps are represented by means of flow line. Circular symbols represent the volumes of flow of cars in the crossroads, and lineal symbols with two colours represent the volumes of flow in the roads, of which one colour represents the cars coming and another going. This set of maps are compiled automatically by digitizer, electronic computer, digital plotter. This paper is illustrated from follwing five parts:type of data and format of observation and record, graphic repressentation and design of symbols, mathematical model, coding and data organizing, data processing and simple introduction of computer mapping technology.