Temporal Geometric Constrained Bundle Adjustment for the Aerial Multi-head Camera System

This paper describes the temporal geometric constrained bundle adjustment method for exterior orientations of individual images acquired from an aerial multi-head camera system without platform calibration parameters and navigation solutions. The aerial multihead camera system provides a single synthetic image, which has large coverage, from precisely estimated exterior orientation parameters (EOP) of each image. The EOP of each image can be directly calculated from navigation solutions and platform geometric calibration parameters. However, if these values are not available for some reason, the EOP of each image can be estimated with control points. In this case, the geometric relationship between camera heads should be considered. Each camera of the multi-head camera system is tightly affixed to the platform; therefore, the geometry between camera heads can be considered a constant. The temporal geometric constraint introduced in this paper is that the relative position (X, Y, and Z) and relative orientation angles (ω, φ, and κ) between cameras heads are the same at different frames (different time instants). This condition can be used as additional observations in the bundle adjustment. Also, small movements or vibration can be considered by selecting proper weights to the constraint. The experiment results show that the temporal geometric constrained approach provides better results, in terms of accuracy as well as precision, than those of the bundle adjustment without constraints. The proposed approach can also be used for calibrating any multihead camera system.