基于 GPS 的先验地图辅助视觉惯性定位方法

In order to improve the localization accuracy of the visual-inertial navigation system, and solve the problem of missing heading information and unable to provide absolute geographic location, a method of visual-inertial simultaneous localization and mapping assisted by prior map generated from GPS is proposed. The GPS geographic coordinates of each frame of image acquisition point are projected into absolute Gaussian coordinates and synchronized with the visual key frame information to build a prior map. The closed-loop detection is carried out by using the bag of words model. The objective optimization function is constructed by the visual reprojection error factor, IMU residual error factor and prior image reprojection error factor, and the least square method is used for the pose estimation and optimization. The proposed method is verified by ground vehicle and low-altitude airborne experiments. The results show that compared with the localization method without prior map, the average location errors in x,y and z directions are reduced by more than 68.2%, 75.1% and 46.4% respectively. And compared with the localization method with prior map(without GPS), the average location errors in x,y and z directions are reduced by more than 34.9%, 51.5% and 19.4% respectively, which improves the localization accuracy of the visual-inertial navigation system in a large-scale environment effectively.