In-flight absolute calibration of an airborne wide-view multispectral imager using a reflectance-based method and its validation

Abstract

The wide-view multispectral imager (WVMI) is the main instrument carried on an unmanned vehicle in the Unmanned Vehicle Payloads Comprehensive Calibration Campaign, which focuses on the calibration and validation of various remote-sensing sensors, including multispectral and hyperspectral sensors. In order to calibrate the WVMI, we designed and deployed a set of six radiometric calibration targets with nominal reflectances of 4%, 20%, 30%, 40%, 50%, and 60% and a set of four radiometric validation targets, the reflectance spectra of which vary dramatically with wavelength. The results reveal a good linear relationship between the digital number (DN) of each sensor and the apparent radiances. Further analysis of data from the validation targets reveals that both spectral unevenness and low reflectance will lead to incurrence of errors in calculations using the calibration equation. This suggests a potential problem that needs to be addressed in the remote sensing of vegetation.