Recently researchers get more and more interested in personalizing wayfinding assistance based on the inte- gration of the individual prior knowledge. A promising approach is the analysis of trajectories recorded with everyday devices. Due to particularities of the sensors, the devices, and the users we need suitable heuristics to extract meaningful data. Additionally, we need spe- cialized tools to simulate, visualize and validate the hypothesis after implementation. In this paper we will present basic considerations, requirements and heuris- tics to estimate spatial knowledge from position sensor data, and we will present our visualization and evalua- tion tool Trackr.