Rainer Mautz

Survey of optical indoor positioning systems

Recent advances in CCD technologies, processing speed and image understanding have been driving the development of the camera-based positioning systems. An improved performance of optical systems has triggered image based positioning methods to become an attractive alternative for applications in industrial metrology as well as for robot- and pedestrian navigation. This paper provides a survey of current optical indoor positioning approaches. Different systems are briefly described and categorized based on how the images are referenced to the environment.

Current investigations at the ETH Zurich in optical indoor positioning

This paper presents a novel approach for a optical indoor positioning system that is currently under development at the Institute of Geodesy and Photogrammetry at the ETH Zurich. The new system is called CLIPS (Camera and Laser based Indoor Positioning System) and it is based on the fundamentals of stereo photogrammetry. The difference to the photogrammetric relative camera orientation is that one camera is substituted for a device emitting laser-beams from a virtual central point. The laser beams project bright spots on any surface in an indoor environment. These laser spots are seen by a camera for the purpose to determine its relative orientation with respect to the laser-device. In chapter II and III some applications and an overview of existing optical indoor positioning systems are given. The last section explains the functionality of the new system CLIPS.

Real-time Indoor Positioning Using Range Imaging Sensors

This paper considers a novel indoor positioning method that is currently under development at the ETH Zurich. The method relies on a digital spatio-semantic interior building model CityGML and a Range Imaging sensor. In contrast to common indoor positioning approaches, the procedure presented here does not require local physical reference infrastructure, such as WLAN hot spots or reference markers.

On the Effect of Localization Errors on Geographic Routing in Sensor Networks

Recently, network localization systems that are based on inter-node ranges have received significant attention. Geographic routing has been considered an application which can utilize the location information from these localization systems. In this paper, we firstly recognize that sensor network localization algorithms generate positioning data with different error patterns compared to those networks where node positions are determined directly from GNSS measurements. Secondly, by simulating practical sensor network scenarios using data from our localization algorithm, we observe that existing geographic routing algorithms in wireless sensor networks (WSNs) adopt very simplistic methods in the treatment of position error, without due consideration of error distribution. Additionally, an insight is given into localization algorithms for WSNs with inhomogeneous error environments. Our observations represent an initial step toward a detailed understanding and design of efficient geographic routing algorithms in location aware WSNs.

Fusion of Building Information and Range Imaging for Autonomous Location Estimation in Indoor Environments

We present a novel approach for autonomous location estimation and navigation in indoor environments using range images and prior scene knowledge from a GIS database (CityGML). What makes this task challenging is the arbitrary relative spatial relation between GIS and Time-of-Flight (ToF) range camera further complicated by a markerless configuration. We propose to estimate the cameras pose solely based on matching of GIS objects and their detected location in image sequences. We develop a coarse-to-fine matching strategy that is able to match point clouds without any initial parameters. Experiments with a state-of-the-art ToF point cloud show that our proposed method delivers an absolute camera position with decimeter accuracy, which is sufficient for many real-world applications (e.g., collision avoidance).

Indoor Positioning and Navigation Using Time-Of-Flight Cameras

The development of indoor positioning techniques is booming. There is a significant demand for systems that have the capability to determine the 3D location of objects in indoor environments for automation, warehousing and logistics. Tracking of people in indoor environments has become vital during firefighting operations, in hospitals and in homes for vulnerable people and particularly for vision impaired or elderly people [1]. Along with the implementation of innovative methods to increase the capabilities in indoor positioning, the number of application areas is growing significantly. The search for alternative indoor positioning methods is driven by the poor performance of Global Navigation Satellite Systems (GNSS) within buildings. Geodetic methods such as total stations or rotational lasers can reach millimeter level of accuracy, but are not economical for most applications. In recent years, network based methods which obtain range or time of flight measurements between network nodes have become a significant alternative for applications at decimeter level accuracy. The measured distances can be used to determine the 3D position of a device by spatial resection or multilateration. Wireless devices enjoy widespread use in numerous diverse applications including sensor networks, which can consist of countless embedded devices, equipped with sensing capabilities, deployed in all environments and organizing themselves in an ad-hoc fashion [2]. However, knowing the correct positions of network nodes and their deployment is an essential precondition. There are a large number of alternative positioning technologies (Fig. 1) that cannot be detailed within the scope of this paper. An exhaustive overview of current indoor position technology is given in [3]. Further focus will be on optical methods.

Indoor Positioning and Navigation. Part III: Navigation Systems

In the age of automation the ability to navigate persons and devices in indoor environments has become increasingly important for a rising number of applications. With the emergence of global satellite positioning systems, the performance of outdoor navigation has become excellent, but many mass market applications require seamless navigation capabilities in all environments. Therefore indoor navigation has become a focus of research and development during the past decade. It has by now become apparent that there is no overall solution based on a single technology, such as that provided outdoors by satellite-based navigation. This Special Issue of the Journal of Location Based Services is the last of three parts where some of the best works presented at IPIN 2011 are revisited and extended. This concluding part addresses navigation systems, with three papers illustrating the state of the art in navigation approaches used in different contexts and level of accuracy. In general, indoor navigation approaches can be divided into two classes: those requiring locally deployed infrastructure (paper I) and those being infrastructure free (papers II and III). The first paper entitled ‘CLIPS – a camera and laser-based indoor positioning system’, by my colleague Sebastian Tilch and myself, describes a camera-based navigation approach at millimetre-level accuracy which requires local infrastructure, even though the deployment is facilitated by projecting the reference points with lasers. All systems requiring dedicated local infrastructure become too costly when scaled to larger coverage areas. Infrastructure free navigation approaches must rely on self-contained sensors. Self-contained sensors can be divided into two classes, as those measuring absolute quantities, e.g. magnetometers, odometers and pressure sensors or sensors capable of measuring only changes of distances or speed such as accelerometers and gyroscopes. The latter group of sensors is used in the common pedestrian dead reckoning approach that is based on an inertial navigation system (INS). Using dead reckoning, an INS-based guidance system is continually adding detected changes to its previously calculated positions. Thus, the accuracy of the propagated position depends heavily on the quality of the provided start position and direction. Most notably, owing to the double integration of noisy accelerometer measurements, INS suffers from accumulation of position deviation and magnification of the angular deviation over the travelled distance (Abbe error). If absolute position or orientation updates are obtained by another sensor source at a high rate, the INS can be used to deliver positions with much higher precision compared to geometric interpolation between supporting points. In pedestrian navigation, the accumulating positioning

SIP for wireless positioning: System and architecture

The recent boom in wireless communications has led to a wide range of new applications. Wireless positioning is an emerging technology which can provide accurate locations for indoor environments when satellite based positioning systems are not available. In this paper, a session initiation protocol (SIP) based system architecture for wireless positioning is described and an overview of how this can be used in overall system architecture has been provided. The proposed system architecture has shown that SIP is competent as a network signaling protocol for wireless positioning

CLIPS – a camera and laser-based indoor positioning system

This article presents a detailed description of an optical indoor positioning system named CLIPS, short for camera and laser-based indoor positioning system. The main objective of CLIPS is pose estimation of a mobile camera with respect to a static projector on a tripod. For that reason, a reference field of red and green laser spots is projected on any surface in an indoor environment. When the reference field is captured by the mobile camera, the geometric relationship between the camera pose and the projector can be established by the coplanarity constraint. Our approach enables full 6 DOF pose estimation of the mobile camera. This article describes the basic concept of CLIPS, the projector calibration, the camera pose estimation and the introduction of the system scale. In addition, the performance of CLIPS regarding achievable accuracy is analysed.

Message of the conference directors

With the emergence of satellite based positioning techniques, outdoor environments have been covered well by GNSS positioning capabilities. Recent focus has shifted towards the indoor environment where the satellite signal propagates poorly. We consider the potential to locate objects and people indoors as a substantial building block for the human development. If we are looking towards seamless positioning in all environments, the indoor environment poses the crux. Several indoor positioning applications are waiting for a satisfactory technical solution in industrial automation, product tracking, stock-keeping, pedestrian navigation in hospitals, homes for the impaired, burning buildings, museums, for the purpose of ambient assisted living, for location based systems and further applications. We frequently get phone calls from companies asking to be advised on their particular indoor positioning application. Unfortunately, we had - until now - to reply that there is no overall solution yet which is all at once reliable, accurate, quickly installed and economical.