DOI: 10.5285/29bf1c9f-a39a-452c-b9f9-de35d9fb9179
title: Orthomosaic of permafrost landscape on Qikiqtaruk - Hershel Island, Yukon, Canada (August 2017)

description: This red-green-blue (RGB) orthomosaic is composite created from 8994 photographs collected withunmanned aerial vehicles (UAVs) over the eastern part of Qikiqtaruk, Herschel Island, in the Canadian Yukon (69.5N, 138.8W). The images were collected on the 10th and 11th of August 2017. Further details on the image processing are provided in the Lineage section. This dataset was created by Andrew Cunliffe, with support from Isla Myers-Smith, William Palmer, Jeffrey Kerby and other members of Team Shrub (https://teamshrub.com/), in order to inform ongoing ecological monitoring studies in this area. Part of this orthomosaic was used for a study into permafrost coastline retreat, published in The Cryosphere (Cunliffe, A. M., Tanski, G., Radosavljevic, B., Palmer, W. F., Sachs, T., Lantuit, H., Kerby, J. T., and Myers-Smith, I. H.: Rapid retreat of permafrost coastline observed with aerial drone photogrammetry, The Cryosphere, 13, 1513-1528, https://doi.org/10.5194/tc-13-1513-2019, 2019).
description: Drone surveys were conducted using two platforms: (i) a lightweight flyingwing Zeta Phantom FX-61 with a PixHawk flight controller equipped with a Sony RX-100ii camera (100 CMOS sensor with 20.2 megapixels) and (ii) a multi-rotor DJI Phantom 4 Pro (100 CMOS sensor with 20 megapixels). Typical flying altitude was between 100 and 120 m above ground level, yielding ground sampling distances of ca. 20 to 40mm, with image overlap of more than nine photographs across most (90%) of the scene.

      Spatial constraint of the orthomosaic was achieved through geotagging of individual camera positions with the UAV location, combined with n=132 black and white ground control markers deployed across the scene and precisely geolocated to an absolute accuracy of approximately 0.02m using real-time kinematic global navigation satellite system (GNSS) equipment (Leica Geosystems).

      These photographs were processed using Agisoft PhotoScan (version 1.3.3) (https://www.agisoft.com/), to a spatial reference system of NAD83 UTM 7N (EPSG: 26907). The following quality settings were used:
Image quality assessment
	Minimum quality score 	&gt;=0.7
Image alignment
	Accuracy: Highest
	Generic preselection: Yes
	Reference preselection: Yes
	Key point limit: 40,000
	Tie point limit: 0
	Adaptive camera model fitting: No
Tie point filtering
	Reprojection error threshold: 0.45
Parameter optimisation:
Enabled parameters: F, Cz, Cy, B1, B2, K1, K2, K3, P1, P2
	Fit rolling shutter: No
Dense cloud
Quality: High
Depth filtering: Mild
Orthomosaic
	Mapping mode: Orthophoto
	Blending mode: Mosaic
	Enable colour correction: Yes
	Enable hole filling: Yes

For additional information on the production and use of this dataset, please refer to: Rapid retreat of permafrost coastline observed with aerial drone photogrammetry, Cunliffe, A. M., Tanski, G., Radosavljevic, B., Palmer, W. F., Sachs, T., Lantuit, H., Kerby, J. T., and Myers-Smith, I. H.: Rapid retreat of permafrost coastline observed with aerial drone photogrammetry, The Cryosphere, 13, 1513-1528, https://doi.org/10.5194/tc-13-1513-2019, 2019 and also the supplementary information accompanying the article.
description: There are some small missing areas within the orthomosaic, due to insufficient image overlap of these areas (nodata is indicated by value of 255 in the Red, Green and Blue bands). Some artefacts (distortion) in the orthomosaic are expected around the periphery of the survey area, particularly where (reflective or moving) water is present.