Airborne Hyperspectral Data Acquisition and Processing in the Arctic: A Pilot Study Using the Hyspex Imaging Spectrometer for Wetland Mapping

Abstract

A pilot study for mapping the Arctic wetlands was conducted in the Yukon Flats National Wildlife Refuge (Refuge), Alaska. It included commissioning the HySpex VNIR-1800 and the HySpex SWIR-384 imaging spectrometers in a single-engine Found Bush Hawk aircraft, planning the flight times, direction, and speed to minimize the strong bidirectional reflectance distribution function (BRDF) effects present at high latitudes and establishing improved data processing workflows for the high-latitude environments. Hyperspectral images were acquired on two clear-sky days in early September, 2018, over three pilot study areas that together represented a wide variety of vegetation and wetland environments. Steps to further minimize BRDF effects and achieve a higher geometric accuracy were added to adapt and improve the Hyspex data processing workflow, developed by the German Aerospace Center (DLR), for high-latitude environments. One-meter spatial resolution hyperspectral images, that included a subset of only 120 selected spectral bands, were used for wetland mapping. A six-category legend was established based on previous U.S. Geological Survey (USGS) and U.S. Fish and Wildlife Service (USFWS) information and maps, and three different classification methods—hybrid classification, spectral angle mapper, and maximum likelihood—were used at two selected sites. The best classification performance occurred when using the maximum likelihood classifier with an averaged Kappa index of 0.95; followed by the spectral angle mapper (SAM) classifier with a Kappa index of 0.62; and, lastly, by the hybrid classifier showing lower performance with a Kappa index of 0.51. Recommendations for improvements of future work include the concurrent acquisition of LiDAR or RGB photo-derived digital surface models as well as detailed spectra collection for Alaska wetland cover to improve classification efforts.

HYPERNOR project: high-resolution hyperspectral camera for microsatellites.

“…The HySpex Heimdal V-3600 N hyperspectral camera for microsatellites is a VNIR pushbroom instrument that is optimized for a small GSD. The camera captures a large amount of spatial data, and, similarly to the HySpex VNIR-1800 camera 13 , this data can be binned to provide a better GSD or to improve SNR. The theoretical specifications of the camera for three operating modes are shown in Table 3.…”

“…There are several objects of various sizes in this image: buildings, an airport apron, a small airplane, small vehicles that are parked next to one of the buildings, etc. (the original image was taken with HySpex VNIR-1800 hyperspectral camera 13 ). The figure demonstrates how objects of different sizes are resolved by the camera operating in different modes.…”

Mapping Alkaline Fens, Transition Mires and Quaking Bogs Using Airborne Hyperspectral and Laser Scanning Data

“…The hyperspectral images were radiometrically, geometrically, and atmospherically corrected. Geometric and atmospheric corrections were performed using PARGE and ATCOR 4 software accordingly (ReSe Applications LLC, Switzerland, [59,60]) and validated using ASD FieldSpec 4 spectral measurements (ASD Inc., Longmont, CO, USA, [61]).…”

Remote sensing from unoccupied aerial systems: Opportunities to enhance Arctic plant ecology in a changing climate

“…To fulfil this need, small piloted airborne platforms have been used, which allows the collection of spatial datasets at sub‐metre resolutions, over large landscapes and away from road systems (Cristóbal et al, 2021; Greaves et al, 2019; Nolan et al, 2015; Wainwright et al, 2021). However, piloted data collection is often expensive, involves certified flight crews and requires strategic flight planning (Chadwick et al, 2020).…”