The radiation characteristic of aerial sensor directly affects the quantitative application level of sensor data. In order to study the radiation characteristic, we carried out the radiation characteristic test based on ground tarps laid onto the calibration field of image quality in Anyang, Henan. The airborne sensor was calibrated adopting reflectance-based method. 8 gray-scale tarps and 4 tarps of high reflectance were laid onto the calibration field and they were all with better Lambert radiation characteristic and spectral performance uniformity. Preliminary results show that the bias is larger and the effective dynamic range is smaller and the SNR is lower but the linearity and repeatability are better which can be used to test the response performance of the sensor. Overall, the radiation characteristic tarps laid on the calibration field are suitable for the study of in-flight radiation characteristic of the aerial digital sensor.
Digital camera is non-metric camera. Its geometric calibration, including the determination of interior orientation elements and distortion parameters, is the base of high precision photogrammetry. In this paper, a laboratory geometric calibration system of digital cameras is developed. This system uses a collimator and a star tester as the target generator. After high precision positioning of targets and corresponding angles of parallel lights, geometric calibration can be accomplished according to the method of this paper. Experiments are taken out based on this system using two kinds of mainstream digital aerial cameras, Cannon EOS 5D Mark II and Hasselblad H3D, and the repeatability experiment is also taken out. Experiment results show that this system can satisfy the calibration requirements of photogrammetric application and the correctness and reliability of the measure precision of this system is verified.
So far, the geometric laboratory calibration system of optical aerial survey camera has been well
established, while there is not a perfect system for digital aerial survey camera and the calibration of
digital camera has not been included in the metrological verification system. In order to make the
photogrammetry project rule-based, it’s imperative to establish geometric laboratory calibration system
of digital survey camera. Exact measuring angle method is the most common method to calibrate the
camera in lab. The sub-pixel sub-division location of spot center for point-source image of digital
camera is one of the key techniques to calibrate the camera based on the exact measuring angle method
in lab. A novel location algorithm is proposed on account of the realities of the lab system. First, the
Gauss filter is introduced to reduce the noise from the stray light and so on. Then the integration of
iterative threshold segmentation and seed region growing is adopted to identify the general location of
the spot. Thirdly, using the bilinear interpolation, the pixels used to estimate the location are increased.
Finally, we use the proposed improved moment method to determinate the precise centroid location of
the digital image. Experimental results show that the spots are identified with 93 percent accuracy and
the centroid accuracy is superior to 1/40 of a pixel and improves about 2 to 4 times than other
algorithms, which indicates that the proposed method is effective, convenient and precision.