Jakob Jakobsen

Low-cost GNSS sampler based on the beaglebone black SBC

This paper describes the design of a simple low cost GNSS sampler with integrated storage. The sampler is built from low cost, off-the-shelf components. The proposed design stores digital IF samples from two separate front ends and record the data to a SD card for post-mission processing. The GNSS sampler currently supports GPS and GLONASS signals, but could also be configured for Galileo reception. The design is based on the popular low cost BeagleBone Black Single Board Computer (SBC) and two evaluation kits of the MAX2769 GNSS Radio Frequency (RF) front end. The design is based on two identical coprocessors in the processor of the BeagleBone, known as Programmable Realtime Units (PRU). The sampler has been designed for portability and data acqusition on small Unmanned Aerial Vehicles (UAVs).

Simulation of GNSS reflected signals and estimation of position accuracy in GNSS-challenged environment

Abstract The paper describes the development and testing of a simulation tool, called QualiSIM. The tool estimates GNSS-based position accuracy based on a simulation of the environment surrounding the GNSS antenna, with a special focus on city-scape environments with large amounts of signal reflections from non-line-of-sight satellites. The signal reflections are implemented using the extended geometric path length of the signal path caused by reflections from the surrounding buildings. Based on real GPS satellite positions, simulated Galileo satellite positions, models of atmospheric effect on the satellite signals, designs of representative environments e.g. urban and rural scenarios, and a method to simulate reflection of satellite signals within the environment we are able to estimate the position accuracy given several prerequisites as described in the paper. The result is a modelling of the signal path from satellite to receiver, the satellite availability, the extended pseudoranges caused by signal reflection, and an estimate of the position accuracy based on a least squares adjustment of the extended pseudoranges. The paper describes the models and algorithms used and a verification test where the results of QualiSIM are compared with results from collection of real GPS data in an environment with much signal reflection.