IEEE Geoscience and Remote Sensing Magazine - September 2019 - 52

occurrence records and the environmental conditions at
occurrence localities [226]. It has been widely applied in
selecting nature reserves, predicting the effects of environmental change on species range, and assessing the risk of
species invasions [227].
Because of the spatial biases and insufficient sampling
of conventional field surveys, UAV-RS has recently become
a highly effective technology for supplying species occurrence data, a result of its ability to quickly and repeatedly acquire high-spatial-resolution imagery at low cost [228]. For
instance, UAV-RS is used to detect plant and animal species
in terrestrial and aquatic ecosystems, estimate their population and distribution patterns, and identify important
habitats (e.g., migratory stopovers and breeding grounds)
[204], [207], [209]. Moreover, UAV-RS provides timely and
on-demand data acquisition, offering a more dynamic way
to understand habitat suitability and species range expansion or contraction.
However, UAV-RS may also cause uncertainty and errors in species distribution modeling. These errors come
mainly from data acquisition and processing algorithms,
such as those involved with species classification. Thus,
strict data acquisition and high-precision data processing
and analysis are necessary.
ENVIRONMENTAL MONITORING AND CONSERVATION
UAVs are used to track environmental processes and
changes at the spatial and temporal scales, which is challenging for conventional remote sensing platforms [1], e.g.,
mudflat evolution and morphological dynamics [229].
Furthermore, environmental pollution monitoring greatly
benefits from UAV-RS. In [230], UAVs equipped with multispectral sensors were employed to map the trophic state of

(a)

(b)
FIGURE 17. A 3D digitalization for cultural heritage site recording

and conservation (taken from Xu et al. [232]): (a) a dense point
cloud of the Gutian conference monument and (b) a photorealistic
3D model of the monument.
52

reservoirs and investigate water pollution for water quality
observation. Soil erosion, degradation, and pollution are
also monitored based on UAV digital terrain models and
orthophotos. For instance, soil copper contamination was
detected based on hydrological models using a multirotor
UAV, and copper accumulation points were estimated at
plot scales based on microrill network modeling and wetland prediction indexes [231].
ARCHEOLOGY AND CULTURAL HERITAGE SITES
The fields of archeology and cultural heritage preservation are
promising areas for UAV-RS [233]. UAVs are generally used to
conduct photogrammetric surveys and mapping, documentation, and preservation of archaeological sites [234]. In addition, the technology is used for archaeological detection and
discovery. In archeology, buried features may produce small
changes or anomalies in surface conditions, which can be detected and measured based on UAVs with spectroradiometer,
digital, or thermal cameras [235].
In the area of cultural heritage sustainment, UAVs are
often employed to produce high-quality 3D recordings
and presentations for documentation, inspection, conservation, restoration, and museum exhibitions [236].
Multiple platforms, e.g., terrestrial laser scanners, ultralight aerial platforms, UAVs, and terrestrial photogrammetry, are often integrated to acquire multiview data for
3D reconstruction and visualization of cultural relics.
In Figure 17, a camera-equipped UAV is integrated with a
terrestrial laser scanner to facilitate complete data acquisition at a historical site, where building façades are captured by the terrestrial laser scanner and building roofs
by UAV photogrammetry [232].
Heritage restoration is usually based on precision 3D
data. In [237], a virtual restoration approach was proposed
for an ancient plank road. The UAV and a terrestrial laser
scanner were used to collect detailed 3D data on existing
plank roads, which were processed to determine the forms
of plank roads and restore each component, with detailed
sizes based on mechanical analysis. The virtual restoration model was then generated by adding components and
background scene into the 3D plank road model.
HUMAN AND SOCIAL UNDERSTANDING
The UAV-RS aerial view makes it a potential solution for
helping to describe, model, predict, and understand human
behavior and social interactions. In [34], UAVs were used
to collect videos of various targets, e.g., pedestrians, bicyclists, cars, and buses, to understand pedestrian trajectories
and their interplay with the physical space as well as with
the targets that populate such spaces. This could provide a
great contribution to pedestrian tracking, target trajectory
prediction, and the understanding of human activity [238].
In [188], researchers used a camera-equipped UAV to record naturalistic vehicle trajectories and the naturalistic behavior of road users, which was intended for scenario-based
safety validation of highly automated vehicles. The data can
IEEE GEOSCIENCE AND REMOTE SENSING MAGAZINE

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IEEE Geoscience and Remote Sensing Magazine - September 2019

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