Lightweight unmanned aerial vehicles will revolutionize spatial ecology

Karen Anderson, Kevin J Gaston
2013 Frontiers in Ecology and the Environment  
R emote-sensing techniques have transformed ecological research by providing both spatial and temporal perspectives on ecological phenomena that would otherwise be difficult to study (eg Kerr and Ostrovsky 2003; Running et al. 2004; Vierling et al. 2008) . In particular, a strong focus has been placed on the use of data obtained from spaceborne remote-sensing instruments because these provide regional-to global-scale observations and repeat timeseries sampling of ecological indicators (eg Gould
more » ... 2000). The main limitation of most of the research-focused satellite missions is the mismatch between the pixel resolution of many regional-extent sensors (eg Landsat [spatial resolution of ~30 m] to the Moderate Resolution Imaging Spectroradiometer [spatial resolution of ~1 km]), the revisit period (eg 18 days for Landsat), and the scale of many ecological processes. Indeed, data provided by these platforms are often "too general to meet regional or local objectives" in ecology (Wulder et al. 2004) . To address this limitation, a range of new (largely commercially operated) satellite sensors have become operational over the past decade, offering data at finer than 10-m spatial resolution with more responsive capabilities (eg Quickbird, IKONOS, GeoEye-1, OrbView-3, WorldView-2). Such data are useful for ecological studies (Fretwell et al. 2012 ), but there remain three operational constraints: (1) a high cost per scene; (2) suitable repeat times are often only possible if oblique view angles are used, distorting geometric and radiometric pixel properties; and (3) cloud contamination, which can obscure features of interest (Loarie et al. 2007 ). Imaging sensors on board civilian aircraft platforms may also be used; these can provide more scale-appropriate data for fine-scale ecological studies, including data from light detection and ranging (LiDAR) sensors (Vierling et al. 2008) . In theory, these surveys can be made on demand, but in practice data acquisition is costly, meaning that regular time-series monitoring is operationally constrained. A new method for fine-scale remote sensing is now emerging that could address all of these operational issues and thus potentially revolutionize spatial ecology and environmental science. Unmanned aerial vehicles (UAVs) are lightweight, low-cost aircraft platforms operated from the ground that can carry imaging or non-imaging payloads. UAVs offer ecologists a promising route to responsive, timely, and cost-effective monitoring of environmental phenomena at spatial and temporal resolutions that are appropriate to the scales of many ecologically relevant variables. Emerging from a military background, there are now a growing number of civilian agencies and organizations that have recognized the possible applications of UAVs, including the National Oceanic and Atmospheric Administration, which states that UAVs "have the potential to efficiently and safely bridge critical information gaps" in data-sparse locations "and advance understanding of key processes in Earth sys- REVIEWS REVIEWS REVIEWS Ecologists require spatially explicit data to relate structure to function. To date, heavy reliance has been placed on obtaining such data from remote-sensing instruments mounted on spacecraft or manned aircraft, although the spatial and temporal resolutions of the data are often not suited to local-scale ecological investigations. Recent technological innovations have led to an upsurge in the availability of unmanned aerial vehicles (UAVs) -aircraft remotely operated from the ground -and there are now many lightweight UAVs on offer at reasonable costs. Flying low and slow, UAVs offer ecologists new opportunities for scale-appropriate measurements of ecological phenomena. Equipped with capable sensors, UAVs can deliver fine spatial resolution data at temporal resolutions defined by the end user. Recent innovations in UAV platform design have been accompanied by improvements in navigation and the miniaturization of measurement technologies, allowing the study of individual organisms and their spatiotemporal dynamics at close range. In a nutshell: • Ecologists require data collected at appropriate spatial and temporal resolutions for a range of studies • Unmanned aerial vehicles (UAVs) can carry various imaging or non-imaging payloads to provide spatial datasets for a variety of end users • The benefits of UAVs are that (1) survey revisit periods (ie the number of repeat flights over a designated site) can be user controlled, (2) low-altitude flight allows sensors to observe the ground from more proximal positions and potentially collect finer spatial resolution data, and (3) operating costs are low • We review current approaches to UAV deployment, summarize their demonstrated and potential applications, and suggest new ways in which UAVs could be used to underpin novel, scale-appropriate environmental science research
doi:10.1890/120150 fatcat:cgavfehar5hzbaq6zct7xqkn6i