Muster, Sina; Langer, Moritz; Heim, Birgit; Westermann, Sebastian; Boike, Julia (2012): Land cover classification of polygonal tundra from small-format aerial photography, Samoylov Island (Lena Delta, Siberia), summer 2008, with link to ESRI grid files [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.786136,

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In supplement to: Muster, S et al. (2012): Subpixel heterogeneity of ice-wedge polygonal tundra: a multi-scale analysis of land cover and evapotranspiration in the Lena River Delta, Siberia. Tellus Series B-Chemical and Physical Meteorology, 64, 17301, https://doi.org/10.3402/tellusb.v64i0.17301

Polygonal tundra on Samoylov Island (Lena Delta, Siberia) was mapped from small-format aerial photography. Sub-metre resolution aerial images were obtained by mounting two Nikon D200 cameras on a helium-filled dirigible. Images were acquired in the visible (VIS) and near-infrared (NIR) ranges (together referred to as the VNIR range). The internal IR-filters were removed from the cameras in a laboratory (LPD LLC, USA), allowing them to capture a maximum range from about 330 to 1200 nm. A Schneider Kreuznach B+W 486 UV-IR cut filter was used for one of the cameras to obtain images in the VIS range, from about 400 to 690 nm, while the second camera was fitted with a Schneider Kreuznach B+W IR-filter 093 to acquire images in the NIR range, above about 830 nm. Flights took place at noon on sunny, cloudless days (August 1, August 9 and August 15, 2008). An average flying altitude of 750 m resulted in a pixel size of about 0.18 m. The aerial image data were processed using ENVI 4.7 image processing software. NIR images were registered onto VIS images using the automatic image-to-image registration with an average root mean square error (RMSE) of 0.53 pixels. The resulting VNIR images were then georeferenced to UTM (WGS84, 52N) based on an orthomosaic of the island from 2007 with a resolution of 0.3 m. The nearest neighbour algorithm was chosen for all resampling operations.

Sixteen images were used to map the ice-wedge polygonal tundra on Samoylov Island, with an image overlap of about 25%. Land cover classification was carried out individually for each VNIR image distinguishing between open water, overgrown water as well as wet and dry tundra. Open water surfaces were extracted using a density slice classification applied to the NIR band. Open water surfaces were subsequently masked, and the remaining three vegetated land cover types, i.e. wet tundra, dry tundra and overgrown water, were classified using a supervised maximum likelihood classifier. Training areas and areas for accuracy assessment were selected from field-based mapping completed in 2006, 2008 and 2010. The relative classification accuracy was calculated by comparing the classifications for overlapping areas of adjacent images. In order to determine the overall classification accuracy, we compared a total of 147 ground-based plots to the final aerial land cover classification. Spurious pixels within a class were changed to conform to that class by applying a majority filter of 11x11 pixels. Areas smaller than 0.5x0.5 m were not included in subsequent analyses.

All classification images were mosaiked in ERDAS as a raster GIS file (ESRI grid).

"Other version" links to an overview image in jpg-format. See doi:10.1594/PANGAEA.786073 for an orthomosaic of Samoylov Island.