. Further by downloading this data the user acknowledges that they agree with the NERC data policy (), and the following conditions:

1. To cite both the data and literature references in any publications that use this data.

DATA REFERENCE:

Andrew M. Cunliffe, Isla H. Myers-Smith, Jeffrey T. Kerby and William F. Palmer.(2019):Orthomosaic of permafrost landscape on Qikiqtaruk - Hershel Island, Yukon, Canada (August 2017). UK Polar Data Centre, Natural Environment Research Council, UK Research & Innovation.

LITERATURE REFERENCE:

A. Cunliffe*, G. Tanski*, B. Radosavljevic, W. Palmer, T. Sachs, H. Lantuit, J. Kerby, and I. Myers-Smith (2019) Accelerating retreat of permafrost coastline observed by combining long-term observations with aerial drone surveys. The Cryosphere. 13(5):1513-1528. doi:10.5194/tc-13-1513-2019

2. The user recognizes the limitations of data and will not use this data for navigation purposes. Use of the data is at the users' own risk, and there is no warranty as to the quality or accuracy of any data, or the fitness of the data for your intended use. The data are not necessarily fully quality assured and cannot be expected to be free from measurement uncertainty, systematic biases, or errors of interpretation or analysis, and may include inaccuracies in error margins quoted with the data.

Methodology:

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 ≥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.

Data quality:

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.