Optimization of two GPS/MEMS-IMU integration strategies with application to sports

The application of low-cost L1 GPS receivers integrated with micro-electro-mechanical system (MEMS) inertial measurement units (IMU) allows the continuous observation of position, velocity and orientation which opens new possibilities for comparison of athletes' performance throughout a racecourse. In this paper, we compare loosely and closely coupled integration strategies under realistic racing scenarios when GPS is partially or completely masked. The study reveals that both integration approaches have a similar performance when the satellite constellation is completed or the outages are short. However, for less than four satellites, the closely coupled strategy clearly outperforms the loosely coupled approach. The second part of the paper is devoted to the important problem of system initialization, because the conventional GPS/IMU alignment methods are no longer applicable when using MEMS-IMU. We introduce a modified coarse alignment method and a quaternion estimation method for the computation of the initial orientation. Simulations and practical experiments reveal that both methods are numerically stable for any initial orientation of the sensors with the error characteristics of MEMS-IMUs. Throughout the paper, our findings are supported by racing experiments with references provided in both, the measurement and the navigation domain

The EGNOS Integrity Concept: Evaluation of the Ionospheric Corrections

Within the validation work of EGNOS for civil aviation, it is interesting to analyze the transmitted corrections individually. In this paper, the ionospheric model of EGNOS is compared to the one determined by an independent organization (CODE). The continuous monitoring of the ionosphere is envisaged in order to analyze the ionospheric corrections in real-time. Two methods based on dual-frequency GPS measurements are described. The first approach computes the ionospheric delays after calibration of the receiver DCB (Differential Code Bias) using phase-smoothed code measurements. The second method is based on spherical harmonic expansions

Galileo et le prix de la mobilité

La monétarisation de la mobilité est un thème qui préoccupe un grand nombre d'acteurs du domaine routier. Quels concepts et quelles technologies ? Comment les faire accepter ? Nombre de questions restent à résoudre. Et que peut apporter la navigation par satellites ? Utopie ou gage de confiance ? Cet article aborde quelques chemins croisés entre navigation et taxe routière

SARFOS - Search And Rescue Forward Operation Support System

Mountain search and rescue in the Alps of Austria and Switzerland is a prominent and challenging example of emergency response tasks. Significant numbers of search and rescue operations are carried out every year. In Switzerland, the "Alpine Rettung" in 2001 served 12'739 mission hours in 431 missions. Of these, 8'193 hours were spent on search missions. 17'229 members served a total of 40'720 hours. Operating in small teams, rescue personnel have to be coordinated overlarge areas, often in rough terrain and adverse weather conditions. Additional assets like helicopters or reconnaissance planes are called in on demand. Operations control typically used a mobile command post (car or van), that is driven close to the area. Due to the number of such tasks and complexity of operations, often with human lives at stake, there is significant demand for assistance by state-of-the-art technology. Key tasks of support are, on the one hand, position, situation and intent reporting of field teams to operations control. On the other hand, operations control needs to forward to field teams operational orders and assistance information, e-g- actual visual or thermal overhead imagery. Thus, there is an important need to exchange data between field teams and operations control ! The purpose of the SARFOS project is to develop a so-called forward emergency response coordination and communication system using a combination of latest technology in the field of integrated satellite and terrestrial communication, navigation and information databases. The answer to the demand identified during requirements analysis is to define, implement and finally demonstrate a prototype system, designed especially for and in cooperation with key mountain rescue services

Redundant MEMS-IMU integrated with GPS for Performance Assessment in Sports

In this article, we investigate two different algorithms for the integration of GPS with redundant MEMS-IMUs. Firstly, the inertial measurements are combined in the observation space to generate a synthetic set of data which is then integrated with GPS by the standard algorithms. In the second approach, the method of strapdown navigation needs to be adapted in order to account for the redundant measurements. Both methods are evaluated in experiments where redundant MEMSIMUs are fixed in different geometries: orthogonallyredundant and skew-redundant IMUs. For the latter configuration, the performance improvement using a synthetic IMU is shown to be 30% on the average. The extended mechanization approach provides slightly better results (about 45% improvement) as the systematic errors of the individual sensors are considered separately rather than their fusion when forming compound measurements. The maximum errors are shown to be reduced even by a factor of 2

Accurate Trajectory and Orientation of a Motorcycle derived from low-cost Satellite and Inertial Measurement Systems

Inertially aided satellite positioning can bring its benefits to all disciplines in which detailed knowledge of the trajectory is a prerequisite for improving performance. In motorcycling for instance, the determination of slips of tires requires the determination of the precise trajectory and the orientation of the motorcycle’s chassis. The correct exploitation of torque or force sensors as well as studies of the vibratory behavior of pneumatics necessitate the knowledge of the orientation of the sensors. Accurate position and orientation can be obtained by integrating inertial measurement units (IMU) with GPS (Global Positioning System). Unfortunately, the traditional, bulky and expensive high-quality GPS/IMU instrumentation is restricted to few disciplines with higher accuracy demands, while the ergonomic constraints of some sports (e.g. ski racing, motorcycling) urge to use devices based on mono-frequency differential GPS and Micro-Electro-Mechanical System (MEMS) inertial technology. Due to their small size, low cost and power consumption, MEMS sensors are suitable for trajectory analysis in sports where ergonomic aspects play an important role. In this article, an experimental low-cost differential GPS/MEMS-IMU system is applied in motorcycling. The system provides an absolute positional accuracy better than 0.5m, velocity estimates accurate to 0.2m/s and an orientation accuracy of 1-2°

L'analyse de performance sportive à l'aide d'un système GPS/INS low-cost: évaluation de capteurs inertiels de type MEMS

Les skieurs s'intéressent au GPS (Global Positioning System) pour évaluer leurs performances. Les positions enregistrées durant les entraînements et les courses permettent d'analyser les trajectoires et de comparer vitesses, accélérations et autres paramètres liés à la performance sportive (p. ex. la fréquence cardiaque). Malheureusement, l'environnement montagneux, la dynamique relativement élevée du skieur et les restrictions ergonomiques dépassent souvent les limites technologiques actuelles

Assessment of the Integration Strategy between GPS and Body-Worn MEMS Sensors with Application to Sports

This paper describes experiments that were performed involving a professional downhill skier equipped with a low-cost L1 GPS receiver and a MEMS-IMU composed of 3 single axis gyroscopes, accelerometers and magnetometers. In addition, the skier carried an L1/L2 GPS receiver and a tactical-grade IMU (LN200). The experiments aimed to assess the navigation performance of different GPS/MEMS-IMU integration strategies compared to high-quality GPS/INS integration. After presenting an overview of currently applied integration methods, the unscented Kalman filter approach in loosely coupled mode. The relevance of the simple MEMS-IMU sensor error model was verified by comparing the filter output to the reference data

Sensor-Augmented EGNOS/Galileo Receiver for Handheld Applications in Urban and Indoor Environments - SARHA

In pedestrian user environments, like dense urban canyons or indoors, the GNSS positioning performance regarding accuracy and availability reaches well-known technological limits. These limitations can be overcome by adding additional sources of information to the system. The main objective of the project ‘SARHA - Sensor-Augmented EGNOS/Galileo Receiver for Handheld Applications in Urban and Indoor Environments’ is the combination of a modern satellite navigation receiver with augmentation and autonomous sensors. Additionally, the hybrid navigation system will be enhanced by a transponder receiver, which communicates with transmitters installed inside buildings, to provide absolute position updates. The transponder will allow the SARHA system to significantly increase reliability and accuracy of the positioning solutions indoors. The hybrid navigation software is split up into two parts. The first one will be implemented directly on the GPS receiver, whereas the second part will run on a microcontroller. In this way a small, low-performance microcontroller can be used, what represents the first step to reduce dimension, weight and energy consumption of the mobile system. The project aims at meeting the requirements of fire fighters, rescue services, police, special task forces, solitary, and lone workers for handheld applications acting in environments with unfavourable satellite signal conditions, using hybrid navigation system architecture. Based on the Galileo signal definitions, analyses are set up to explore the signal characteristics in comparison to the GPS signals. Improvements due to Galileo signal availability in urban and indoor environments are assessed and will later ensure seamless integration of enhanced technologies into continuous developments