Name: Thermokarst Flight Lines

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Description: Flight lines were planned using a priori information including known areas of exemplary thermokarst landscapes, existing permafrost study sites, a 2016-2017 Sentinel-2 mosaic of 10-m spatial resolution, and a NWT-wide change detection product based on Landsat Tasseled Cap trend analysis (courtesy of Government of Northwest Territories, NWT Centre for Geomatics). Surveys were planned throughout the Taiga Plains (except for the most southern region), Taiga Cordillera (Mackenzie Valley Foothills, Richardson Plateau, Mackenzie Mountains), Taiga Shield (High Boreal, Low Boreal, Low Subarctic), and the Southern and Northern Arctic.The foci areas were covered to the degree possible given weather, aircraft and fuel supply limitations. The aerial survey spanned a total of 50 suitable flying days within a two-year period. Both Bell 407 and Aerospatiale A-Star helicopters were used for survey work. The airborne transects totaled over 26,500 km. From an regional representation perspective, the transects intersected seven Level II ecoregions in the NWT (Taiga Cordillera/Plains/Shield, Boreal/Tundra Cordillera as well as Southern/Northern Arctic, six mainland Level III ecoregions in the NWT, and 78 Level IV ecoregions (Ecosystem Classification Group, 2009).Survey altitude averaged 250 to 350 m Above Ground Level for all regions, but depended daily on the type, topography and weather conditions of the transect. Surveys were conducted at typical cruise speeds of 190-200 km/h (GPS ground speed). Hard-copy maps and Garmin handheld GPS units (62S, Montana 680) were used for navigation, and transect lines typically deviated from what was planned a priorid ue to weather or site prioritization.Along the transects a detailed and large-scale record of thermokarst and permafrost landscape features was captured via digital images, geographic locations (tracklogs) and tabulated observational information. Data from one or several Garmin handheld GPS receivers (.GPX format) were imported into a file geodatabase as seperate feature classes and manually inspected for quality/consistency. These feature classes were merged whereby GPS locations associated with ground visits were deleted. A "Date" string attribute was added for each sample. Lines were generated from the cleaned observations using ArcGIS "Points to Line" tool, with the Date field as Line Field and the DateTime field as the Sort Field. Transects with missing handheld GPS information were manually digtized based on GPS tags from photo records, field survey forms, and field notes. Flight line distances (in kilometer) were calculated based on NAD83 CSRS with respective UTM zone projection.Data governanceData owner and discipline authority: NT Geological Survey.Data custodian: NWT Centre for Geomatics.Data stewards: shared responsibility between NT Geological Survey and NWT Centre for Geomatics.Date of last update: November, 2022.Update cycle: annually.Suggested citation for photo dataset: Van der Sluijs, J., Kokelj, S.V., Rudy, A.C.A. 2022. Geomatics field- and web-methodologies supporting a systematic aerial inventory and characterization of thaw-sensitive permafrost terrain in the Northwest Territories.

Copyright Text: The data collection and processing procedures were produced by J. van der Sluijs, S.V. Kokelj and A.C.A. Rudy, Northwest Territories Centre for Geomatics and Northwest Territories Geological Survey as a data product to support the Thermokarst Collective Permafrost Mapping Project.

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