PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
April 2014
291
Unmanned Aerial Systems (UAS) for Soil
Assessment, Validation, and Monitoring
Small unmanned aerial systems (sUAS), which are consid-
ered aircraft with attendant sensors that operate with no
human pilot onboard, have been developed over the past few
decades for both military and civilian purposes. Such sys-
tems hold considerable promise for soil scientists, given the
capability of UAS to be deployed quickly and programmed
to acquire imagery and geospatial data at high spatial and
temporal resolutions, especially in landscapes where soil
investigations occur in rugged terrain, remote regions with
limited access, or pose considerable risk to field personnel
(Plate 3). Current applications of sUAS focus on production
agriculture to help maximize yields and reduce environmen-
tal impacts by improving nitrogen and water management
and reducing nitrate leaching or nitrous oxide emissions
/
To date, there have been limited applications of UAS to
soil investigations. Such applications are focused on assess-
ing erosion processes or mapping and modeling vegetation
conditions and dynamics without explicit linkage to selected
soil properties (Dandois and Ellis, 2013; Laliberte et al.,
2010; Peter et al., 2014; Rasmussen et al., 2013). Potential
applications could be targeted to mapping soil patterns,
mapping terrain derivatives estimated from real-time li-
dar-based digital elevation model, and validating boundary
conditions along transects in rugged terrain (Plate 3).
Active and Passive Microwave Measurements
of Global Soil Moisture
NASA is scheduled to launch the Soil Moisture Active Pas-
sive (SMAP) satellite into low Earth orbit in November 2014
(
/). The mission purpose is to provide
global mapping of soil moisture and freeze-thaw state. The
resulting information will aid understanding of global wa-
ter, energy, and carbon cycles, advance climate science, and
improve weather and agricultural yield forecasting. The
satellite will carry active radar and a passive microwave
radiometer to measure the backscatter and emission of micro-
wave energy from the Earth’s surface, from which global soil
moisture maps will be derived. These maps will also inform
water management decisions and contribute to flood and
drought monitoring, among other applications of benefit to
society (Brown et al., 2013; Entekhabi et al., 2010) (Plate 4).
Plate 2
. Soil observations and measurements using traditional visual means (upper left) and visible-near infrared diffuse
reflectance spectroscopy under field and laboratory settings (upper right, lower left, respectively) with resulting spectral
plot indicating reflectance properties of soil horizons, or layers.
