Radiometric Correction of MultiSpectral Cameras Using Photosensor Irradiance for Agronomy Applications

Cloud coverage has a significant impact on the reflectance maps generated by multispectral cameras mounted on UAV\u27s in small farm settings. The current approach is to calibrate the camera once before every flight and use the radiometric calibration map for the entire flight. In this work we have designed and built a downwelling and upwelling photosensor to work in sync with our custom multispectral camera. A dual reflectance panel implementation for the time dependent radiometric calibration of the multispectral camera is completed. The solar spectral irradiance curve is approximated using the current measurements from the downwelling photosensor and the ground truth curve using a spectrometer. A multilinear regression algorithm was used for this purpose. The solar spectral irradiance curves are used during image acquisition to modify the initial radiometric calibration mapping function. This has potential to improve the usage of the multispectral camera under a wide range of weather conditions