Alaska Satellite Facility - Distributed Active Archive Center

How to Radiometrically Terrain-Correct (RTC) Sentinel-1 Data Using the ESA Toolbox

Before and after RTC: In this detail from the test granule below, mountains in Bolivia (left) appear stretched on one side and compressed on the other. RTC (right) moves pixels to unstretch the mountains and adjusts pixel values to subtract the effect of slopes on brightness. Credit left: Copernicus Sentinel data 2015. Credit right: ASF DAAC 2016, contains modified Copernicus Sentinel data 2015, processed by ESA. 

Source: ASF Staff

Easier (Windows, Mac, or Unix): Use a GUI to correct distortions in synthetic aperture radar (SAR) images one at a time