Development of a Low-Cost Integrated Navigation System for USVs
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This report considers the real-time implementation approach of an integration between an Inertial Navigation System (INS) and a Global Positioning System (GPS). The integration has been performed, using a GlobalSat EM--411 GPS receiver and a Microstrain 3DM--GX1 Inertial Measurement Unit (IMU). This has been performed by incorporating a Kalman filter, and aiding the INS estimates through GPS measurements. The goal of this thesis is to create an integrated application able to achieve performance of existing solutions three times the cost. The implementation has been made in real-time in c++, and off-line in Matlab. However the c++ code has not been sufficiently tested due to computer processing problems. Also the code has not been tested on an actual unmanned surface vehicle. The integrated solution worked sufficently when the GPS was online. However, during GPS droupout, the result is subject to high position drift, resulting in position errors of up to 400 meters after 20 seconds. Although it is unknown quite how large the position deviation of other, existing solutions are. However, high drift during GPS dropouts renders the IMU estimates quite useless for navigation. Thus this experiment has been unsuccessful.