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. […]
