Document Type

Article

Publication Date

4-15-2020

Abstract

This study provides a systematic comparison of lidar, Multibeam Echo Sounders (MBES), and Structure-from-Motion (SfM) derived datasets collected over a fixed surface contained within a large outdoor flume converted to a 15 × 2.5 × 1.5 m tank. The surface incorporated various morphological features and structures for measurement technique comparison over varying surface type and geometries. Two lidar scans and two photograph sets (used in SfM) capture the subaerial surface within the experimental tank before and after the tank was filled for MBES measurements. MBES surveys at varied frequencies (200 and 400 kHz), swath widths (90° and 150°), and phase/amplitude blends (0 and 84%) settings were conducted along longitudinal transects. Post-processing of the data delivers three-dimensional point clouds that are georeferenced via RTK-GNSS measurements of control points within the experimental tank. All datasets are compared to the first lidar dataset (lidar1), herein defined as the reference surface. Calculated root mean square error (RMSE) for each dataset results in 0.3–3.37 cm error among the three systems under the experimental conditions. Datasets are then detrended to determine how each instrument detects individual geomorphic features at various resolutions. The wide swath width of the MBES generated the largest difference between surfaces, which may be attributed to echoing from the cement tank walls. Error found among techniques suggest that caution should be used when resolving textures < 3.5 cm with MBES, but is dependent on distance and point spacing during the survey.

Publication Source (Journal or Book title)

Geomorphology

Number

518

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