Inside GNSS Media & Research

JUL-AUG 2019

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64 Inside GNSS J U L Y / A U G U S T 2 0 1 9 www.insidegnss.com tories over the course of the experi- ment. Figure 23(b) shows the Doppler measured by the MATRIX SDR and the estimated Doppler using satellite posi- tion and velocity obtained from TLE fi les and an SGP4 propagator for the 2 Orbcomm satellites. To estimate the UAV's trajectory, 3 frameworks were implemented to esti- mate the UAV's trajectory: (i) the LEO- aided INS STAN framework initialized using TLE fi les, (ii) the LEO-aided INS STAN framework that used the decod- ed periodically transmitted LEO satel- lite positions, which were transmitted by the Orbcomm satellites, and (iii) a traditional GPS-aided INS for com- parative analysis. e estimated trajec- tories were compared with the trajec- tory extracted from the UAV's onboard navigation system. Each framework had access to GPS for only the fi rst 125 seconds. Figure 24(a) shows the trajec- tories that the 2 Orbcomm LEO satel- lites traversed over the course of the experiment. Figure 24(b)-(d) illustrate the UAV's true trajectory and those estimated by each of the 3 frameworks. Table 5 summarizes the final error and position RMSE achieved by each framework a er GPS cutoff . Manufacturers In the Ground Vehicle Navigation sec- tion, the authors' setup included an Ettus E312 universal so ware radio peripheral (USRP) from Ettus Research (Austin, Texas, USA) to sample Orbcomm sig- nals; an AsteRx-I V integrated GNSS- IMU from Septentrio (Leuven, Belgium and Torrance, California, USA); a VectorNav VN-100 microelectrome- chanical systems (MEMS) IMU from VectorNav Technologies (Dallas, Texas, USA); and Septentrio's post-processing software development kit (PP-SDK) was used to process GPS carrier phase observables collected. In t he experiment conducted to evaluate the performance of the LEO- aided INS STAN framework on a UAV, a DJI Matrice 600 UAV with an A3 fl ight controller was used (Shenzhen, China); again, the setup included an Ettus E312 USRP from Ettus Research (Austin, Texas, USA). Acknowledgements This work was supported in part by the Office of Naval Research (ONR) under the Young Investigator Program (YIP) award and in part by the National Science Foundation (NSF) CAREER award under Gra nt 1929965. The authors would like to thank Christian Ardito, Linh Nguyen, Ali Abdallah, Mohammad Orabi, Kimia Shamaei, Mahdi Maaref, and Naji Tarabay for their help in data collection. FIGURE 24 Results of the UAV experiment. (a) Orbcomm satellite trajectories. (b)-(d) UAV's true and estimated trajectories. Map data: Google Earth. Additional Resources (1) Ardito, C., J. Morales, J. Khalife, A. Abdallah, and Z. Kassas, "Performance evaluation of navigation using LEO satellite signals with periodically transmitted satellite positions," in Proceedings of ION International Technical Meeting, 2019, pp. 306-318. (2) Autonomous Systems Perception, Intelligence, and Nav igation (A SPIN) Laboratory http://aspin.eng.uci.edu (3) Brown R., and P. Hwang, Introduction to Random Signals and Applied Kalman Filtering, 3rd ed. John Wiley & Sons, 2002. (4) Driusso, M., C. Marshall, M. Sabathy, F. Knutti, H. Mathis, and F. Babich, "Vehicular position tracking using LTE signals," IEEE Transactions on Vehicular Technology, vol. 66, no. 4, pp. 3376–3391, April 2017. (5) Fang, S., J. Chen, H. Huang, and T. Lin, "Is FM a RF-based positioning solution in a met- ropolitan-scale environment? A probabilistic approach with radio measurements analysis," IEEE Transactions on Broadcasting, vol. 55, no. 3, pp. 577–588, September 2009. (6) Federal Communications Commission, "FCC boosts satellite broadband connectivity and competition in the united states," https:// Unaided INS LEO-aided INS STAN LEO-aided INS STAN with periodically transmitted satellite positions Final Error (m) 123.5 29.9 5.7 RMSE (m) 53.7 15.9 5.4 Table 5: Experimental results with 2 Orbcomm LEO satellites for a UAV navigating about 1.53 km in 155 seconds (GPS signals were cut off after the fi rst 125 seconds). These results are after GPS cutoff . FIGURE 23 (a) Skyplot of the Orbcomm satellite trajectories. (b) Doppler frequency measurement produced by the MATRIX SDR and the expected Doppler according to an SGP4 propagator for the UAV experiment. STAN WITH LEO

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