Indoor navigation and modeling using photographed evacuation plans and MEMS IMU

In this paper, we present an approach for the modeling of building interiors by a user who is equipped with a navigation system, which integrates MEMS IMU data processing with automatic interpretation of photos of evacuation plans. Such emergency plans for the evacuation of buildings are compulsory for public buildings in a number of countries. They consist of an approximate floor plan, the current position and escape routes. Additionally, semantic information like stairs, elevators or the level number may be found. If an image of such a floor plan is captured by a potential user, this information is made explicit again by a suitable raster-to-vector conversion. The resulting approximate indoor building model can then refined by semi-automatic data collection. Similar to outdoor scenarios like OpenStreetMap, features of interest can be collected interactively while the user moves through the building. By these means the entrances of rooms, positions of windows, facilities etc. can be integrated into the available indoor model. However, this presumes a suitable positional accuracy during indoor navigation. This is realized using inertial measurements from a low-cost MEMS IMU. Their evaluation by a ZUPT-(zero velocity update)-based algorithm is further supported by integrating information from the evacuation plan like the initial position of the user at the location of the plan. Furthermore, typical constraints for indoor environments like detected stairs or an assumed movement parallel to outer walls are applied to eliminate drift effects of the used low-cost sensor system. This provides a suitable accuracy to allow for an efficient map refinement.