Grassroots September 2016, Vol. 16, No. 3 | Page 23
Feature
The role of remotely piloted aircrafts (RPA’s) in rangeland
monitoring
Christiaan Harmse and Hannes Gerber
Northern Cape Department of Agriculture, Land Reform and Rural Development (Research Unit)
[email protected] / [email protected]
One of the primary objectives of rangeland
monitoring is to determine if grazing management
strategies meet the goals for sustainable resource
utilization and to prevent rangeland degradation
from taking place (James et al., 2003). However,
monitoring is an ongoing process nneeded to
determine whether progress is being made towards
the achievement of objectives on given variables
such as prolonged droughts, veld fires, grazing
pressures, land-use
use and climate change. Ground
surveys can be time consuming, labour intensive,
logistically
tically challenging in remote areas and,
therefore, very expensive (Gardner et al., 2008).
Depending on the scale, the objectivity and
representativeness of ground based assessments can
at times be questioned since surveys cannot be
conducted at the frequency
ncy required for proper
analysis and monitoring of trends due to high cost
implications and inaccessibility. Therefore, a
significant weakness in ecological research and
rangeland monitoring in southern Africa’s
rangelands remains its inability to easily ttrack
changes in vegetation structure and composition
resulting from management strategies, land
land-use and
climate change (Koh&Wich, 2012). This can
further be attributed to the lack of access to high
resolution geospatial data sets (Mishra et al., 2015).
Therefore,
refore, rangeland monitoring is often neglected
and the question must be asked, whereto with
rangeland monitoring in the 21st centur
century?
Grassroots
Figure 1: High quality geo-referenced
geo
image
captured by a RPA (a) with a clear distinction
possible between individual grass tufts compared to
(b) a lower quality satellite image with only larger
woody plants barely visible as darker patches.
Ground resolutions and sensor capabilities of
satellites have improved immensely within recent
years (Whitehead et al., 2014). While
Whil remote
sensing technologies are evolving at a rapid rate,
most researchers currently rely on satellite based
remote sensing for mapping and monitoring
(Broich et al., 2011). Even though certain low
resolution satellite images are freely available (e.g.
Landsat
andsat and MODIS), other sub-meter
sub
resolution
images (such as IKONOS, Worldview and
Quickbird) can be extremely costly and may not
always offer timely high resolution images to fulfil
the objectives required (Koh&Wich, 2012).
Remote sensing images from satellites
sat
are also
often obscured by cloud cover, preventing any realreal
time monitoring (Hansen et al., 2008; Koh&Wich,
2012). Therefore, only a few studies utilizing high
resolution remote sensing data, such as Wessels et
al. (2007) and Wessels et al. (2012) have been
undertaken in southern Africa rangelands.
September 2016
Vol 16 No. 3