Inside GNSS Media & Research

MAR-APR 2018

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Page 44 of 67 M A R C H / A P R I L 2 0 1 8 Inside GNSS 45 attenuation, and signal shadowing. Furthermore, sections sur- rounded by farmland are covered with dry snow causing signal reflection and multipath effects. During all tests, the measurement noise of the GNSS observables is calculated using a function of the Signal to Noise Ratio (SNR) measured by the receiver. For the naviga- tion filter's differential mode, the correction data is received in RTCM-V3 format using the N-trip protocol via broadcast. Due to poor internet connectivity, especially along the mid- dle part of the test track, a continuous update of differential data cannot be guaranteed. Since Konrad et alia (Additional Resources) proved the RTK suitability as reference system for static and dynamic conditions, a RTK capable receiver is used for reference purposes. e platform on which the navigation filter is running is a Rapid Control Prototyping (RCP) system for real-world evaluation tests. e RCP real- time hardware is a 900 megahertz single core system. For inertial measurement, the setup utilizes an indus- trial-class IMU-sensor that provides accelerations, angular rates and magnetometer measurements at a rate of 100 hertz. A receiver provides the required GNSS observables with an update rate of 10 hertz. e communication link between these two devices is realized via serial interface. In addition, communication and process delays can be determined and compensated using a PPS signal. Figure 4 provides the evaluation results of the test campaign. e first plot gives the 2D-error of the three introduced GNSS pre-processing modes. Here, the 2D error means the difference between the EKF solution and the position of the reference system. e accuracy of this 2D-error calculation depends on the accuracy of the reference system. erefore, the fourth sub- figure gives the mode of the reference receiver, which switches between the precise RTK fix and less precise differential GPS modes due losses in differential data updates. Switches of the reference receiver mode can result in jumps on the 2D-error. e second sub-plot shows the satellite availability of the GPS and the Galileo system. A closer look is taken on GPS and Galileo satellites, which FIGURE 3 Challenging conditions on the real-world test environment LEO in Bavaria, Germany Our closed loop and open loop MEMS accelerometer families are expanding! Additional grades of our MAXL-CL-3030 tailored to meet the needs of our customers Tactical and inertial grade performance 15g-70g sensing range closed loop accelerometer 2g-70g sensing range open loop accelerometer Visit our booth #13 at IEEE/ION PLANS (Monterey, CA) April 23-26, 2018 Schedule a meeting at AUVSI Xponential (Denver, CO) May 1-3, 2018 Visit our booth in the Israeli Pavilion at Eurosatory (Paris, FR) June 11-15, 2018

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