The paper describes a map generation system which relies on random individual contributions of GPS traced movements. In a typical use case, mobile phone users would join a specific community to contribute their movements along streets, roads or pathways in form of so called traces. Neither contributing subscribers nor the map generation need to have an a priori knowledge of the charted area. The approach presented here comprises the trace recording, the upload process to a common server and the processing algorithm for map generation. The problem of noisy data, resulting from GPS inaccuracies and random movements is addressed and countermeasures are proposed. One major perspective of this paper is the decomposition of a map into reasonable segments. In this context, the filter mechanism applied to the raw data is a key component for the deduction of precise street maps. Furthermore, the proof of concept is given and a guideline for a lower limit of active subscribers to achieve an operational system is derived.