Improving the accuracy of mems IMU/GPS POS systems for land-based mobile mapping system by using tightly coupled integration and auxiliary odometer

Mobile mapping system (MMS) has developed rapidly over the past two decades. In that system, a direct geo-referencing system using Global Positioning System (GPS) and Inertial Navigation System (INS) is applied to determine the time-variable position and orientation parameters. The Kalman filter is used as an optimal estimation tool for real-time INS/GPS integrated kinematic position and orientation determination. The loosely coupled (LC) system is commonly used as an INS/GPS integration approach due to its simplicity to derive navigation information. However, in the urban area, since there is usually less than four GPS satellites can be tracked, the INS errors will grow as a function of time during GPS signal outages. In that case, tightly coupled (TC) integration should be beneficial in such poor GPS signal reception environments because the measurement updates can be provided even if there are less than four satellites in the sky. Additionally, vehicle body velocities provided by the odometer are used to minimize the POS errors during GPS signal gaps.