Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
The Cryosphere, 10, 1665-1677, 2016
http://www.the-cryosphere.net/10/1665/2016/
doi:10.5194/tc-10-1665-2016
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
01 Aug 2016
An automated methodology for differentiating rock from snow, clouds and sea in Antarctica from Landsat 8 imagery: a new rock outcrop map and area estimation for the entire Antarctic continent
Alex Burton-Johnson1, Martin Black1,2, Peter T. Fretwell1, and Joseph Kaluza-Gilbert3 1British Antarctic Survey, Cambridge, CB3 OET, UK
2Department of Geography, Environment and Earth Sciences, University of Hull, Hull, HU6 7RX, UK
3School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
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.

Citation: Burton-Johnson, A., Black, M., Fretwell, P. T., and Kaluza-Gilbert, J.: An automated methodology for differentiating rock from snow, clouds and sea in Antarctica from Landsat 8 imagery: a new rock outcrop map and area estimation for the entire Antarctic continent, The Cryosphere, 10, 1665-1677, doi:10.5194/tc-10-1665-2016, 2016.
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Short summary
We present a new rock outcrop map for the entire Antarctic continent, a principal base dataset for research and mapping in Antarctica with broad applications. To derive the map, a new methodology was developed and applied to allow automated identification of rock outcrops from Landsat 8 satellite images whilst excluding sunlit and shaded snow, clouds and liquid water – the first such automated methodology. The new dataset reveals that exposed rock forms only 0.18 % of the entire continent.
We present a new rock outcrop map for the entire Antarctic continent, a principal base dataset...
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