Development and Testing of a UAV Laser Scanner and Multispectral Camera System for Eco-Geomorphic Applications

Christopher Tomsett,Julian Leyland

doi:10.3390/s21227719

Abstract

While Uncrewed Aerial Vehicle (UAV) systems and camera sensors are routinely deployed in conjunction with Structure from Motion (SfM) techniques to derive 3D models of fluvial systems, in the presence of vegetation these techniques are subject to large errors. This is because of the high structural complexity of vegetation and inability of processing techniques to identify bare earth points in vegetated areas. Furthermore, for eco-geomorphic applications where characterization of the vegetation is an important aim when collecting fluvial survey data, the issues are compounded, and an alternative survey method is required. Laser Scanning techniques have been shown to be a suitable technique for discretizing both bare earth and vegetation, owing to the high spatial density of collected data and the ability of some systems to deliver dual (e.g., first and last) returns. Herein we detail the development and testing of a UAV mounted LiDAR and Multispectral camera system and processing workflow, with application to a specific river field location and reference to eco-hydraulic research generally. We show that the system and data processing workflow has the ability to detect bare earth, vegetation structure and NDVI type outputs which are superior to SfM outputs alone, and which are shown to be more accurate and repeatable, with a level of detection of under 0.1 m. These characteristics of the developed sensor package and workflows offer great potential for future eco-geomorphic research.

Highlights

In hydrology and fluvial geomorphology, the use of Uncrewed Aerial Vehicle (UAV) and Structure from Motion (SfM) has been extensively reviewed [5,6]; eco-geomorphic and eco-hydraulic applications have been limited to land cover and vegetation classification mapping exercises based on high-resolution ortho-imagery, rather than derivation of 3D scene characteristics relating to terrain and vegetation structure
This paper has focused mainly on the development and application of a UAV-based laser scanning system, but the purpose for developing such a sensor package is for research into eco-geomorphic processes along river corridors
0.1 m, we have shown that sensors imum level of detection at 0.1 m, we have shown that UAV laser scanning (UAV-LS) and UAV-MS sensorsare are capable of delivering high-resolution 3D point clouds and imagery which are able to capable of delivering high-resolution 3D point clouds and imagery which are able to disdiscretize vegetation structure and spectral response

Summary

Introduction

The use of Uncrewed Aerial Vehicles (UAVs) with camera sensors and associated Structure from Motion (SfM) techniques has proliferated in recent years with the development of small, high-endurance aircraft, high-quality lightweight camera sensors, processing software, and increased computer processing power [1]. The versatility of platforms and applications has led to a proliferation of studies within the Earth sciences [2] and beyond [3,4], becoming one of the most widely used high-resolution topographic data collection techniques for characterizing small to medium (100 –101 km2 ) areas. In hydrology and fluvial geomorphology, the use of UAVs and SfM has been extensively reviewed [5,6]; eco-geomorphic and eco-hydraulic applications have been limited to land cover and vegetation classification mapping exercises based on high-resolution ortho-imagery, rather than derivation of 3D scene characteristics relating to terrain and vegetation structure.

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