Marker Based Activity Transition Models

A client device for gathering mobility information of a user is described. The device comprises a sensor data obtaining means for collecting sensor data representative for transportation-characteristic information of a user and a marker information obtaining means for collecting marker information, the marker information being related to an environmental characteristic of the user or an activity of the user not determined based on a transportation characteristic. The system also comprises a processing means for combining the transportation-characteristic information of the user and the marker information so as to be able to determine based thereon mobility information of the user. The system also comprises an output means for outputting the combined transportation-characteristic information and the marker information. A corresponding server device, method and computer implemented inventions also are disclosed.