Mitigating thermal-induced image drift for videogrammetric technique in support of structural monitoring applications

The thermal effect that leads to spurious image drift is one major concern in the videogrammetric measurement. On the ground that the image drift originates from the thermal-induced displacement of the image sensor board, this study proposes to establish the thermal-induced displacement function of the image plane for the prediction of image drift and the elimination thereof. The displacement function of the image plane is calibrated with stationary targets easily available in laboratory. In measurements other than the thermal effect calibration, the thermal-induced displacement of the image plane is predicted from the precalibrated displacement function. It is then subtracted from the measured pixel coordinates of measurand, resulting in normalized pixel coordinates in which the thermal-induced image drift has been removed. To exemplify this approach, two thermal effect calibration tests with different camera orientations are fulfilled. The displacement function of the image plane is simulated with a first-order polynomial model. Verification tests are performed in both temperature-controlled and outdoor environments. The approach achieves satisfactory performance in both environments.