Review article: Feature tracing in radio-echo sounding products of terrestrial ice sheets and planetary bodies

Abstract. Radio-echo sounding (RES) is a useful technique for measuring the subsurface properties of ice sheets and glaciers.  One of the most important and unique outcomes is the mapping of ice sheets' englacial layer stratigraphy, mainly consisting of isochronous reflection horizons. Mapping those is still a labour-intensive task. This review provides an overview of state-of-the art (semi-)automated methods for identifying ice surface, basal, and internal reflection horizons from radargrams in radioglaciology.  We discuss a variety of methods which were developed or applied to RES data over the last decades, including image processing, statistical techniques, and deep learning approaches. For each approach, we briefly summarize their procedures, challenges, and potential applications. Despite major advances, we conclude that gaps remain in effectively mapping internal reflection horizons in an automated way, but with deep learning representing a potential advancement. This paper aims to inform researchers and practitioners in radioglaciology about current and future trends in mapping the englacial stratigraphy of ice sheets.