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.

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is a research ecologist and research fellow, and Gavin M. 15 Siriwardena is the head of terrestrial ecology and principle ecologist for the British 16

-The measurement of spectral data in the field has an important role in remote sensing, and a long history, but instruments and methods to achieve this have serious limitations under all but the most ideal conditions. Problems arise from the instruments themselves, from the environment in which they are used, and from the methodologies that are commonly adopted.The variable most commonly sought from field measurements is spectral reflectance, or more strictly the bidirectional reflectance factor (BRF), but this is dependent to some extent on the instrument used to make the measurement, and the conditions of measurement, notably the sky irradiance distribution. In this paper we argue that field spectral measurements should be recorded in the appropriate SI units, which will normally be the derived units of radiance for the flux reflected from the target and irradiance for the incident energy. Reflectance data remain a convenient way to represent the energy interactions occurring at the surface, and they have value in generic spectral libraries, but ultimately they lack reproducibility unless accompanied by much more detailed metadata than is the norm in most spectral libraries.

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