Recalibration of a Stereoscopic Camera System for In-Flight Wing Deformation Measurements

The applicability of wing deformation measurements techniques based on stereoscopic photogrammetry has already been demonstrated for in-flight applications. The position and alignment of a stereoscopic camera setup is described in the external parameters of the camera calibration by a rotation matrix and a translation vector. Especially at dynamic flight manoeuvres varying multidirectional loads and the vibration level can affect the camera installation and induce slight changes in the camera position and alignment. Those camera movements induce a decalibration of the measurement system and affect the accuracy of the results directly. The paper describes criteria to assess the decalibration level of a stereo camera system. An approach for a recalibration and its limits are demonstrated for a dynamic wing deformation measurement performed on an Evektor Cobra VUT100 airplane by means of the Image Pattern Correlation Technique (IPCT). IPCT combines the principles of stereoscopic photogrammetry with image correlation methods to determine corresponding areas in a stereo image pair and delivers the 3D wing shape as result. The measurement was part of the project ‘Advanced In-Flight Measurement Techniques 2’ (AIM²) funded by the 7th Framework Programme for Research of the EU