Abstract
Abstract. As the accuracy and sensitivity of remote-sensing satellites improve, there is an increasing demand for more accurate and updated base datasets for surveying and monitoring. However, differentiating rock outcrop from snow and ice is a particular problem in Antarctica, where extensive cloud cover and widespread shaded regions lead to classification errors. The existing rock outcrop dataset has significant georeferencing issues as well as overestimation and generalisation of rock exposure areas. The most commonly used method for automated rock and snow differentiation, the normalised difference snow index (NDSI), has difficulty differentiating rock and snow in Antarctica due to misclassification of shaded pixels and is not able to differentiate illuminated rock from clouds. This study presents a new method for identifying rock exposures using Landsat 8 data. This is the first automated methodology for snow and rock differentiation that excludes areas of snow (both illuminated and shaded), clouds and liquid water whilst identifying both sunlit and shaded rock, achieving higher and more consistent accuracies than alternative data and methods such as the NDSI. The new methodology has been applied to the whole Antarctic continent (north of 82°40′ S) using Landsat 8 data to produce a new rock outcrop dataset for Antarctica. The new data (merged with existing data where Landsat 8 tiles are unavailable; most extensively south of 82°40′ S) reveal that exposed rock forms 0.18 % (21 745 km2) of the total land area of Antarctica: half of previous estimates.
Highlights
Differentiating areas of snow and exposed rock in Antarctica is important in a variety of contexts, including mapping; navigation; glaciological, geological and geomorphological research; and monitoring changes in the ice sheet and its response to climate change
The only existing continentwide geospatial dataset for exposed rock in Antarctica is available from the Scientific Committee on Antarctic Research (SCAR) Antarctic Digital Database (ADD) website, http://www.add.scar.org
The manually derived land cover was compared with the existing ADD rock outcrop dataset, the new automated method and the optimum normalised difference snow index (NDSI)-determined output for each image
Summary
Differentiating areas of snow and exposed rock in Antarctica is important in a variety of contexts, including mapping; navigation; glaciological, geological and geomorphological research; and monitoring changes in the ice sheet and its response to climate change. The only existing continentwide geospatial dataset for exposed rock in Antarctica is available from the Scientific Committee on Antarctic Research (SCAR) Antarctic Digital Database (ADD) website, http://www.add.scar.org. This dataset (the ADD rock outcrop dataset; Thomson and Cooper, 1993) has been derived through manual identification and digitisation of published topographic maps. As satellite-derived coastlines and digital elevation models become available, the inconsistency and inaccuracy of the present cartographically derived ADD rock outcrop dataset becomes difficult to resolve with these new data sources.
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