How Image Acquisition Geometry of UAV Campaigns Affects the Derived Products and Their Accuracy in Areas with Complex Geomorphology

Aggeliki Kyriou,Ioannis Koukouvelas,Konstantinos Nikolakopoulos

doi:10.3390/ijgi10060408

Aggeliki Kyriou, Ioannis Koukouvelas + Show 1 more

Open Access

https://doi.org/10.3390/ijgi10060408

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Abstract

The detailed and accurate mapping of landscapes and their geomorphological characteristics is a key issue in hazard management. The current study examines whether the image acquisition geometry of unmanned aerial vehicle (UAV) campaigns affects the accuracy of the derived products, i.e., orthophotos, digital surface models (DSMs) and photogrammetric point clouds, while performing a detailed geomorphological mapping of a landslide area. UAV flights were executed and the collected imagery was organized into three subcategories based on the viewing angle of the UAV camera. The first subcategory consists of the nadir imagery, the second is composed of the oblique imagery and the third category blends both nadir and oblique imagery. UAV imagery processing was carried out using structure-from-motion photogrammetry (SfM). High-resolution products were generated, consisting of orthophotos, DSMs and photogrammetric-based point clouds. Their accuracy was evaluated utilizing statistical approaches such as the estimation of the root mean square error (RMSE), calculation of the geometric mean of a feature, length measurement, calculation of cloud-to-cloud distances as well as qualitive criteria. All the quantitative and qualitative results were taken into account for the impact assessment. It was demonstrated that the oblique-viewing geometry as well as the combination of nadir and oblique imagery could be used effectively for geomorphological mapping in areas with complex topography and steep slopes that overpass 60 degrees. Moreover, the accuracy assessment revealed that those acquisition geometries contribute to the creation of significantly better products compared to the corresponding one arising from nadir-viewing imagery.

Highlights

Over the past few decades, scientists have drawn attention to global climate change as the analysis of emissions indicate that greenhouse gases are increasing [1]
The current study examines whether the image acquisition geometry of unmanned aerial vehicle (UAV) campaigns affects the accuracy of the derived products, while performing a detailed geomorphological mapping of a landslide area
The current study examined the effect of UAV image acquisition geometry on the accuracy of the derived products in order to achieve a detailed geomorphological mapping

Summary

Introduction

Over the past few decades, scientists have drawn attention to global climate change as the analysis of emissions indicate that greenhouse gases are increasing [1]. Research of areas prone to natural disasters as well as the construction of protective measures is based on a detailed and accurate mapping of all the geomorphological characteristics of a landform. The utilization of UAVs in precision mapping seems to be more effective compared to the classical topographic survey, resulting in the creation of orthophotos and digital surface models (DSMs) with extremely fine resolution [8]. In this context, high-resolution and low-cost data obtained by UAVs could potentially be used to create and update maps by providing orthophotos with sub-decimeter accuracy [9]. UAV-based point clouds and DSMs prove comparable to corresponding products arising from terrestrial laser scanning (TLS) survey [10]

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