Drones for litter monitoring on coasts and rivers: suitable flight altitude and image resolution

Umberto Andriolo; Konstantinos Topouzelis; Tim H M van Emmerik; Apostolos Papakonstantinou; João Gama Monteiro; Atsuhiko Isobe; Mitsuko Hidaka; Shin'ichiro Kako; Tomoya Kataoka; Gil Gonçalves

doi:10.1016/j.marpolbul.2023.115521

Drones for litter monitoring on coasts and rivers: suitable flight altitude and image resolution

Mar Pollut Bull. 2023 Oct:195:115521. doi: 10.1016/j.marpolbul.2023.115521. Epub 2023 Sep 13.

Affiliations

¹ INESC Coimbra, Department of Electrical and Computer Engineering, Polo 2, 3030-290 Coimbra, Portugal. Electronic address: uandriolo@mat.uc.pt.
² Department of Marine Sciences, University of the Aegean, Greece. Electronic address: topouzelis@marine.aegean.gr.
³ Hydrology and Environmental Hydraulics Group, Wageningen University, Wageningen, the Netherlands. Electronic address: tim.vanemmerik@wur.nl.
⁴ Department of Civil Engineering and Geomatics, University of Technology, Lemesos, Cyprus. Electronic address: a.papakonstantinou@cut.ac.cy.
⁵ MARE - Marine and Environmental Sciences Centre/ARNET - Aquatic Research Network, Agência Regional para o Desenvolvimento da Investigação Tecnologia e Inovação (ARDITI), Funchal, Madeira, Portugal; Faculty of Life Sciences, Universidade da Madeira, Funchal, Madeira, Portugal. Electronic address: jmonteiro@mare-centre.pt.
⁶ Research Institute for Applied Mechanics, Kyushu University, Kasuga, Japan. Electronic address: aisobe@riam.kyushu-u.ac.jp.
⁷ Research Institute for Value-Added-Information Generation (VAiG), Japan Agency for Marine - Earth Science and Technology (JAMSTEC), Yokohama, Japan; Graduate School of Science and Engineering, Department of Engineering, Ocean Civil Engineering Program, Kagoshima University, Kagoshima, Japan. Electronic address: mitsukou@jamstec.go.jp.
⁸ Graduate School of Science and Engineering, Department of Engineering, Ocean Civil Engineering Program, Kagoshima University, Kagoshima, Japan. Electronic address: kako@oce.kagoshima-u.ac.jp.
⁹ Department of Civil and Environmental Engineering, Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan. Electronic address: kataoka.tomoya.ab@ehime-u.ac.jp.
¹⁰ INESC Coimbra, Department of Electrical and Computer Engineering, Polo 2, 3030-290 Coimbra, Portugal; University of Coimbra, Department of Mathematics, Coimbra, Portugal. Electronic address: gil@mat.uc.pt.

PMID: 37714078
DOI: 10.1016/j.marpolbul.2023.115521

Abstract

Multirotor drones can be efficiently used to monitor macro-litter in coastal and riverine environments. Litter on beaches, dunes and riverbanks, along with floating litter on coastal and river waters, can be spotted and mapped from aerial drone images. Items detection and classification are prone to image resolution, which is expressed in terms of Ground Sampling Distance (GSD). The GSD is determined by drone flight altitude and camera properties. This paper investigates what is a suitable GSD value for litter survey. Drone flight altitude and camera setup should be chosen to obtain a GSD between 0.5 cm/px and 1.25 cm/px. Within this range, the lowest GSD allows litter categorization and classification, whereas the highest value should be adopted for a coarser litter census. In the vision of drawing up a global protocol for drone-based litter surveys, this work sets the ground for homogenizing data collection and litter assessments.

Keywords: Environmental pollution; Ground Sampling Distance; Plastic; Remote sensing; UAV.