Assistance data for indoor positioning is generated with vertical access areas, such as stairs, elevators, and escalators, identified along with predicted vertical movement models for the vertical access area. The predicted vertical movement models provide probabilities of movement to different floors by the vertical access areas. The assistance data may be generated by acquiring a floor plan data for a structure having multiple floors and analyzing the floor plan data to detect vertical access areas. The predicted vertical movement model for the vertical access area may then be generated and included in the assistance data along with the vertical access area. Mobile devices using the assistance data may provide vertical access area feedback information that may be used to modify the assistance data. For example, the probability of movement to different floors by a vertical access area may be modified, or additional vertical access areas identified.