Airborne hyperspectral imaging for wetland mapping in the Yukon Flats, Alaska

Thesis (M.S.) University of Alaska Fairbanks, 2020This study involved commissioning HySpex, a hyperspectral imaging system, on a single-engine Bush Hawk aircraft; using it to acquire images over selected regions of the Yukon Flats National Wildlife Refuge; establishing a complete processing flow to convert raw data to radiometrically and geometrically corrected hypercubes, and further processing the data to classify wetlands. Commissioning involved designing a customized mount to simultaneously install two-camera systems, one operating in the visible and near infrared region, and the other operating in the shortwave infrared region. Flight planning incorporated special considerations in choosing the flight direction, speed, and time windows to minimize effects of the Bidirectional Reflection Distribution Function (BRDF) that are more dominant in high latitudes. BRDF effects were further minimized through a special processing step, that was added to the established hyperspectral data processing chain developed by the German Space Agency (DLR). Instrument commissioning included a test flight over the University of Alaska Fairbanks for a bore-sight calibration between the HySpex system's two cameras, and to ensure the radiometric and geometric fidelity of the acquired images. Calibration resulted in a root mean square error of 0.5 pixels or less for images acquired from both cameras at 1-meter spatial resolution for each geometrically corrected flight line. Imagery was radiometrically corrected using the ATCOR-4 software package. No field spectra of the study areas were collected due to logistics constraints. However, a visual comparison between current spectral libraries and acquired hyperspectral image spectra was used to ensure spectral quality. For wetlands mapping, a 6-category legend was established based on previous United States Geological Survey and United States Fish and Wildlife Service information and maps, and three different classification methods are used in two selected areas: hybrid classification, spectral angle mapper, and maximum likelihood. Final maps were successfully classified using a maximum likelihood method with high Kappa values and user's and producer's accuracy are more than 90% for nearly all categories. The maximum likelihood classifier generated the best wetland classification results, with a Kappa index of about 0.90. This was followed by the SAM classifier with a Kappa index of about 0.57 and lastly by the hybrid classifier that achieved a Kappa index of only 0.42. Recommendations for future work include using higher-accuracy GPS measurements to improve georectification, building a spectral library for Alaskan vegetation, collection of ground spectral measurements concurrently with flight image acquisition, and acquisition of LiDAR or RGB-photo derived digital surface models to improve classification efforts.United States Fish and Wildlife Service, Alaska NSF EPSCoR, College of Natural Science and Mathematics at the University of Alaska Fairbanks, UAF Graduate Schoo

Novel applications of remote sensing and GIS in mass wasting hazard assessments for two fjords of South-Central Alaska

Dissertation (Ph.D.) University of Alaska Fairbanks, 2021The fjords of South-Central Alaska are dynamic environments and host to a number of natural hazards that have not received much attention from the research community. The cities of Seward and Whittier are two of Alaska's most important marine transportation hubs, home to commercial fishing fleets, termini of the Alaska Railroad, and home to thousands of residents. This doctoral research focuses on landslides and their associated hazards in these under-studied areas. Chapter 2 involves surficial mapping of the study areas and documents the role of the underlying geologic processes that threaten the safety of people and infrastructure in the Passage Canal-Portage Valley area (including the town of Whittier), to better inform community planning, mitigation, and emergency response activities. Chapter 3 builds on the successes and lessons learned from the mapping efforts made in Chapter 2. A surficial geology and landslide inventory map were made using very high resolution orthoimagery, DEMs, and 3D models which were viewed in an immersive Virtual Reality (iVR) system. Chapter 4 examines the hazards associated with large amounts of sediment entering the alluvial fan system from further upslope. A collection of six Digital Elevation Models (DEMs) and meteorological data collected over a ten-year period were used to estimate flood-related sedimentation. Uncertainties in each DEM were accounted for, and a DEMs of Difference (DoD) technique was used to quantify the amount and pattern of sediment introduced, redistributed, or exiting the system. The study shows that the DoD method and using multiple technologies to create DEMs is effective in quantifying the volumetric change and general spatial patterns of sediment redistribution between the acquisition of DEMs. Correlations of the changes in sediment budget with rainfall data and flood events were made. During the years of average rainfall, the reaches in the corridor experienced an overall decrease in sediment load, while heavy rainfall events both saw large influx of new sediment and the reworking of existing sediment. This research is the first to collect and use high resolution data for generating digital elevation models, for using a DoD method for mapping elevation changes over time, and for using these products along with available ancillary data for a hazard assessment in these regions. This doctoral work lays out a solid foundation for further work in hazard assessment that will also guide decision-makers in the future on mitigation measures in these important population centers in south central Alaska.State of Alaska Division of Geologic & Geophysical Surveys, the Seward Bear Creek Flood Service Area , the UAF Geophysical Institute, the Alaska EPSCoR program, and the Alaska Space Grant programChapter 1: General introduction. Chapter 2: Inventory and preliminary assessment of geologic hazards in the passage Canal-Portage Valley area, South-Central Alaska. Chapter 3: Improving surficial geology and mass wasting hazard mapping with virtual reality. Chapter 4: Quantifying debris flood deposits in an Alaskan fjord using multitemporal digital elevation models. Chapter 4: Conclusions. Appendices