Nicholas J Spore

Surf Zone Characterization Using a Small Quadcopter: Technical Issues and Procedures

We explore the potential for using a small unmanned aerial vehicle (UAV) quadcopter to collect long-dwell imagery of the nearshore from which important measurements can be made at low cost and with flexibility. This paper extends the existing topographic imaging approaches that rely on having plentiful ground control spread across the image, to the nearshore case where the bulk of the image is water with no control point and vehicle metadata must be used. The UAV autopilot was found to be capable of excellent station-keeping with the positional errors of 0.20 and 0.53 m (horizontal and vertical) and the viewing angle errors of 0.25° (tilt and roll) and 0.38° (azimuth). The ground position of imaged objects could be found with 0.21-m accuracy. Metadata returned by the UAV on camera position was accurate at 5 m, and the camera roll could be assumed to be 0°, reducing the ground control requirements to two, or even one location. Even under this extreme simplification, ground position errors averaged only 10 m but were worse for cases when only control points near to the UAV were used. A model for the visual contrast of waves when viewed from different angles found that large tilts are important but, in contrast to theory, that there was little dependence on the viewing azimuthal angle. Derived Argus products agreed well with the same products collected using a traditional fixed Argus station. UAVs appear to be a very promising alternate to fixed camera systems if limited duration sampling is adequate.

Coastal Foredune Evolution, Part 1: Environmental Factors and Forcing Processes Affecting Morphological Evolution

Abstract : This Coastal and Hydraulics Engineering Technical Note (CHETN) is the first of two CHETNs focused on improving technologies to forecast coastal foredune evolution. Part 1 summarizes the short-, meso-, and multi-decadal-timescale environmental factors and forcing processes that influence the morphodynamic evolution of coastal foredunes. Part 2 reviews modeling approaches to forecast these changes and develops a probabilistic modeling framework to calculate foredune evolution that includes both erosion and growth processes.

Foredune Classification and Storm Response: Automated Analysis of Terrestrial Lidar DEMs

Abstract : Accurate predictions of foredune response and recovery to storms arecritical for understanding coastal vulnerability at a variety of time-scales. Foredunemorphology and storm response were investigated using terrestrial lidar data along a10-kilometer stretch of open-coast beach near Duck, NC. An algorithm was developedto classify foredune state from 50-cm bare earth DEMs into four categories: scarped,recovering, healthy, and man-made. The algorithm was based on extraction ofmorphological features including the slope, volume, and curvature of the foreduneface. Preliminary results detailing the response of each foredune state to a 4-dayNorEaster (Hs = 4.8m at 16s in 8m of water) are presented, and suggest that manmadeand recovering dunes lost more volume and eroded more rapidly whencompared with scarped dunes. The increased erosion may have been due to acombination of slightly lower dune-toe elevations for the man-made dunes andunconsolidated sediment in the foredune.

Evaluation of Unmanned Aircraft Systems for Flood Risk Management : Field Experiment Conspectus

The 2017 Duck Unmanned Aircraft Systems (UAS) Pilot Experiment was designed to evaluate existing and new UAS-based survey and monitoring techniques beneficial to U.S. Army Corps of Engineers Flood Risk Management (FRM). The diverse array of UAS sensors (lidar, multispectral packages, and high-resolution cameras) can collect data to estimate topography, bathymetry, terrain, land cover, vegetation, and structures at high temporal and spatial resolution. The experiment took place on 5–24 June 2017 at the U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, Field Research Facility. Nine UAS flight teams from the federal government, academia, and the private sector conducted 180 UAS flights with 10 different UAS platforms as well as 2 traditional fixed-wing plane overhead surveys. The UAS flights combined for over 2,782 minutes of air time across estuarine, dune, beach, and nearshore environments, including various types of natural features and man-made infrastructure. Such datasets provide the foundation for quantitatively comparing the pros and cons of different platforms, sensor packages, and processing techniques against each other as well as traditional survey methods. This special report summarizes the cooperative June 2017 UAS for FRM pilot field experiment; sections detail participating groups, airframes, field preparation/field operations, and data dissemination. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.

Collection, processing, and accuracy of mobile terrestrial lidar survey data in the coastal environment

Abstract : The purpose of this Coastal and Hydraulics Engineering technical report is to present how elevation data is collected along the coast using terrestrial lidar scanners coupled with a global position system/inertial navigation system and assess the accuracy of the data. A brief overview of the technology utilized on the vehicle platform is presented, along with upcoming improvements. This is followed by a description of the data processing techniques utilized to create three-dimensional point clouds. Subsequent to that is a presentation of an accuracy assessment to provide an overall system performance summary and provide a few examples of data products and their uses. The accuracy assessment of the system resulted in a mean horizontal error of 0.075 meter (m), mean vertical error of 0.099 m, mean total error of 0.129 m, and an average repeatability of 0.05 m. The results of this report suggest that assigning a single accuracy value to a mobile lidar survey may misrepresent some of the spatially variable error throughout the survey, and further work should incorporate full error propagation to each point.