Empirical line calibration of WorldView-2 satellite imagery to reflectance data: using quadratic prediction equations

Obtaining accurate quantitative spectral information from raw multispectral satellite imagery requires the conversion of raw digital numbers (DNs) to units of radiance or reflectance. In this article, an empirical line method is used to calibrate WorldView-2 satellite imagery to surface reflectance. Prediction equations for the eight multispectral bands were developed using a non-linear relationship between sensor top-of-atmosphere spectral radiance (L TOA) and surface reflectance values obtained from seven field targets. An accuracy assessment was undertaken by comparing image reflectance values against the surface reflectance values of 19 independent field targets. The overall accuracy based on the root mean square error (RMSE) for the eight bands ranged between 0.94% and 2.14% with the greatest variance in the near-infrared (NIR) bands. The results of this study show that empirical line methods can be used to successfully calibrate WorldView-2 satellite imagery to reflectance data.