First results from supporting long coherent CDMA correlations by a MEMS INS and a Pedestrian Navigation System for HS-GNSS applications

This paper introduces a new approach to perform very long coherent integration for HS-GNSS applications developed under ESA funded project “DINGPOS”. Very long coherent integration is an approach to increase a GNSS receiver's post-correlation signal-to-noise ratio (SNR) and is especially helpful in the indoor scenario. For successful coherent integration very precise signal replicas have to be created. Taking into account an integration time in the second domain, the user motion has to be determined precisely. For that reason an Inertial Measurement Unit (IMU) has been chosen to track the user motion. Due to several constraints a MEMS-type IMU has to be used, hence the low performance of this sensor kind is denying the use of a classical strap-down calculation. The paper introduces an innovative approach using a Pedestrian Navigation System (PNS) as backbone for the system, taking comfort of the low drift and high macroscopic accuracy of that system. Using this position knowledge as a priori information, a corrected pseudo strap-down calculation can be used to produce a micro-trajectory of sufficient accuracy for replication of the GNSS signals. Finally an integration time of 2 seconds for a walking user shall be achieved. The paper discusses the need for that special procedure, the elements of the integrated system, the alternative processing of the micro-trajectory reproduction and discusses some initial results.