Boike, Julia; Veh, Georg; Stoof, Günter; Grüber, Maren; Langer, Moritz; Muster, Sina (2015): Visible and near-infrared orthomosaic and orthophotos of Samoylov Island, Siberia, summer 2008, with links to data files. Alfred Wegener Institute - Research Unit Potsdam, PANGAEA, https://doi.org/10.1594/PANGAEA.847343
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Latitude: 72.376480 * Longitude: 126.489230
Date/Time Start: 2008-07-30T00:00:00 * Date/Time End: 2008-07-30T00:00:00
Minimum Elevation: 8.0 m * Maximum Elevation: 8.0 m
We obtained sub-meter resolution aerial images of Samoylov Island 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 on August 1, August 9, August 15, and September 11, 2008. Flight altitudes ranged from about 400 m about 1000 m.
Obtained images were used to produce
(i) single VNIR orthophotos and
(ii) two orthomosaics in the visible and the near-infrared range each.
Single orthophotos 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 using an orthomosaic of the island with a resolution of 0.3 m from 2007 (doi:10.1594/PANGAEA.786073). We chose the nearest neighbour algorithm for all resampling operations.
For the VIS (NIR) orthomosaic 232 (245) images were used for stereo photogrammetric processing using Agisoft Photoscan (V 188.8.131.527). The decisive criteria for image selection were the absence of clouds and the image sharpness. Hence, no pictures from the northern/ northwestern part of the island met these criteria. No measured Ground Control Points (GCPs) were available to enhance the image's georeference. In ArcGIS (V 10.2.2), an evenly distributed network of 91 "Virtual Ground Control Points was pegged out across the whole island based on the Orthomosaic Samoylov from the year 2007" (doi:10.1594/PANGAEA.786073). Overall reprojection error was 0.77 m for the VIS mosaic and 0.73 m for the NIR mosaic.
Projection of all orthophotos and orthomosaics is UTM WGS84, 52N.
9 data points