This cross-calibration is a vital step not only to establish the relative calibration of the satellite sensors but also to ensure that data from multiple sensors can be used to provide a consistent set of measurements. The current work focuses on the cross-comparison of L8 OLI to L7 ETM+. The ETM+ sensor has been extremely stable since launch and successfully operating for over a decade and has been used by researchers for a number of cross-calibration studies [19,25,27]. The use of the ETM+ sensor, in this study, will provide a first order estimate of OLI calibration as compared to the stable ETM+ sensor. It should be noted that a similar cross calibration approach has been used to tie all the Landsat Multispectral Scanner (MSS) suites of sensors (MSS1–MSS5) to L5 TM and L5 TM to L7 ETM+ [24,25].