Modular tightly coupled system with clock error estimation for multi-GNSS for road vehicle applications in urban scenarios

In most areas of application of GNSS positioning the use of standalone calculation or loosely coupling is sufficient. With high-end GNSS receivers and high-precision IMUs these algorithms provide a good performance as long as the availability of satellites is adequate. Using GPS gives this condition in many cases. In the automotive area several challenges arise: Urban canyons cause shadowing effects and multipath errors. Besides the receiver and sensors must be affordable and in the line with the budget of vehicle production. So this work investigates the performance improvement of a tightly coupled algorithm using multi-GNSS instead of using only one system. Further it evaluates the approach of a modular update routine. This modularization enables the independent update of different parts of system state vector. To use multi-GNSS separate clock error estimation for each system is made. In the process of evaluation the different position results are compared with broadcast intersystem bias (ISB) where possible.