Calibration of WorldView-2 satellite imagery to reflectance data using an empirical line method

Obtaining accurate quantitative information from multispectral satellite data requires the conversion of raw digital numbers (DN) to reflectance. Sensor characteristics, illumination geometry and atmospheric conditions affect the signal received by a multispectral satellite sensor. In this paper an empirical line method is used to calibrate an eight band multispectral WorldView-2 image. Correction for illumination geometry and atmospheric attenuation in the imagery was achieved by developing a non-linear relationship between top of atmosphere (TOA) spectral radiance and surface reflectance values measured from field targets, using an (ASD Inc) FieldSpecPro spectrometer. An accuracy assessment was undertaken by comparing image reflectance values against the surface reflectance values of 17 field targets. The overall accuracy based on the RMSE for the eight bands ranged between 0.69 – 2.35% with the greatest variance in the near infrared bands. The results of this study show that empirical line methods can be used to successfully calibrate WorldView-2 satellite imagery to reflectance data.