ANALYSIS OF THE RADIOMETRIC DISTORTIONS OF THE TETRACAM ADC LITE CAMERA

Abstract

A number of works using Unmanned Aerial Vehicles (UAV) have been taking advantage of the ADC Lite multispectral camera by Tetracam. The images acquired by the camera have been qualitatively and quantitatively analyzed by many authors without previously correcting radiometric distortions, which is mandatory for practical and academic purposes. In this paper we made it clear that distortions such as the read noise, pixels non-uniform response to the incoming radiance and the vignetting effect are present in the ADC images. Beside these distortions, the weighting values in the Color Processing File (CPF), provided by Tetracam and used to interpolate the Bayer filter, delivers wrong bright values in a number of situations, causing information loss, particularly in the Red band, producing very high frequencies (~10⁵) of black saturated pixels. The correction of these effects and remaining noise artifacts in the image frame (caused by the color interpolation) is mandatory when working with them, which is clearly demonstrated in this paper when we calculated a normalized band ratio from the raw and corrected images.