Automated delineation and characterization of drumlins using a localized contour tree approach |
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| Institution: | 1. Department of Geography & Geographic Information Science, University of Cincinnati, Cincinnati, OH, USA;2. Department of Geography, Binghamton University, State University of New York, Binghamton, New York, USA;3. Department of Geology, University of Cincinnati, Cincinnati, OH, USA;1. College of Mechatronics and Automation, National University of Defense Technology, Changsha, Hunan 410073, PR China;2. Naval Academy of Armament, Beijing 100036, China;1. School of Water Conservancy & Environment, Zhengzhou University, 450001 Zhengzhou, China;2. Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, 100101 Beijing, China |
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| Abstract: | Drumlins are ubiquitous landforms in previously glaciated regions, formed through a series of complex subglacial processes operating underneath the paleo-ice sheets. Accurate delineation and characterization of drumlins are essential for understanding the formation mechanism of drumlins as well as the flow behaviors and basal conditions of paleo-ice sheets. Automated mapping of drumlins is particularly important for examining the distribution patterns of drumlins across large spatial scales. This paper presents an automated vector-based approach to mapping drumlins from high-resolution light detection and ranging (LiDAR) data. The rationale is to extract a set of concentric contours by building localized contour trees and establishing topological relationships. This automated method can overcome the shortcomings of previously manual and automated methods for mapping drumlins, for instance, the azimuthal biases during the generation of shaded relief images. A case study was carried out over a portion of the New York Drumlin Field. Overall 1181 drumlins were identified from the LiDAR-derived DEM across the study region, which had been underestimated in previous literature. The delineation results were visually and statistically compared to the manual digitization results. The morphology of drumlins was characterized by quantifying the length, width, elongation ratio, height, area, and volume. Statistical and spatial analyses were conducted to examine the distribution pattern and spatial variability of drumlin size and form. The drumlins and the morphologic characteristics exhibit significant spatial clustering rather than randomly distributed patterns. The form of drumlins varies from ovoid to spindle shapes towards the downstream direction of paleo ice flows, along with the decrease in width, area, and volume. This observation is in line with previous studies, which may be explained by the variations in sediment thickness and/or the velocity increases of ice flows towards ice front. |
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| Keywords: | Drumlin Contour tree LiDAR Morphology Spatial pattern |
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