Location Determination in Indoor Environments for Pedestrian Navigation

Abstract

For the location determination of persons and objects in indoor environments a variety of systems have been developed in recent years. The main methods are described and compared in this paper, i.e., location methods using infrared, ultrasonic or radio signals and optical tracking systems. Thereby it can be distinguished if the system is specially designed for positioning and has to be installed in the building or if already available infrastructure (such as WiFi, UWB or Bluetooth) is employed. The indoor location techniques can be integrated in modern navigation systems where also a location determination of the user in a building is required apart from positioning in urban outdoor environments. As most common indoor location techniques provide only 2-D position determination, however, a challenging task is to determine the correct floor of a user in a multi-storey building. In this case it can be recommended to augment the positioning system with a barometric pressure sensor for direct observation of height differences. In the research project NAVIO (Pedestrian Navigation Systems in Combined Indoor/Outdoor Environements) conducted at our University tests with different sensors have been performed. The tests have shown that it is possible to determine the correct floor of a user using a barometric pressure sensor as the standard deviation of the estimation of the height differences is better than ± 1 m. Currently a combination of WiFi positioning with a barometric pressure sensor and other dead reckoning sensors (for observation of the direction of motion and traveled distance) is tested in our office building. A typical application would be the guidance and navigation of a pedestrian who is unfamiliar with the environment to a a certain office or a person at the Vienna University of Technology. The selcted approach and test results will be presented in the paper. number of mobile locating applications. In this paper an overview of indoor location techniques is given followed by a more detailed analysis of the use of Wireless Local Area Network (or WiFi) signals for indoor location determination. Recent performance test results of the WiFi positioning system 'ipos' in a localization testbed are presented. For 3-D location determination the system will be augmented with a barometric pressure sensor for direct observation of the altitude in the building. Using this sensor we are able to determine the correct floor of a user in a multi-storey building. Test results using the Vaisala pressure sensor PTB 220 are presented. In addition, other dead reckoning sensors for the measurement of the traveled distance and the direction of motion (or heading) are also necessary in a pedestrian navigation system and have been integrated in the design of the NAVIO system. The employed sensors are presented and their integration using a multi-sensor fusion model is briefly described.