A Convolutional Neural Network-Based Relative Radiometric Calibration Method

Due to the degeneration problem of sensors, calibration becomes a prerequisite step to retrieve consistent satellite images, especially for the ones from long-term time series. Relative calibration is an economic manner to address the problem. Previous studies leverage the identified no-change pixels (NCPs) between two images for relative calibration. However, the identification of NCPs itself is a very hard task and the inferior detection quality affects the performances significantly. Inspired by the great success of deep learning techniques, in this article, we first develop a convolutional neural network (CNN)-based relative calibration method, which bypasses the NCP detection. In particular, the ratio of sensor sensitivity coefficients at two time points is directly estimated by feeding the corresponding image pair into our developed CNN regressor. A polynomial function is fitted upon the estimated ratios in time series. We train the CNN regressor based on the multisite calibration results and then conduct experiments on FengYun-3A (FY-3A), FengYun-3B (FY-3B), and FengYun-3C (FY-3C). The results validate the effectiveness of the proposed method, and it outperforms state-of-the-art NCP-based methods.