Spatial images to study crop health
Ranjith Alankara with the
IWMI drone for a test flight in Colombo
Photo: Neil Palmer /IWMI
High spatial resolution images captured by drones are bettering those
generated by satellites, and enabling researchers in Sri Lanka to study
crop health and irrigation in greater detail.
A team of the International Water Management Institute (IWMI) has
been testing the Swiss-manufactured eBee, or Electronic Bee in the skies
above the Anuradhapura District, this September.
"Usually, the clear sky window doesn't coincide with a satellite
pass," says Salman Siddiqui, head of the organization's geographic
"With a near infrared sensor on board, the e-Bee can help us or
farmers identify stress in a crop 10 days before it actually shows up
physically," says Siddiqui. Multiple images taken by a drone can be
stitched together to produce a digital surface or elevation model in
virtual 3D. These can, for example, help identify areas vulnerable to
16 megapixel camera on-board the e-Bee boasts a spatial resolution of
up to three centimetres which is significantly more detailed than images
generated, for instance, by Google Earth which clocks in at five metres.
The drone also allows scientists to determine the frequency with which
images are updated. In contrast, satellites data is usually refreshed
only every 15 days or so. "Another major factor is the cost of satellite
images, particularly when the area has to be covered several times,"
The e-Bee can spend up to 45 minutes in the air on a single charge of
its batteries. Its sensors keep it stable through shifting winds and
allow it to avoid other objects that might be sharing its airspace.
On completion of mission, the e-Bee lands automatically, guided by
its artificial intelligence module and the global positioning system.
P.M.P. Udayakantha, Sri Lanka's surveyor general, expects that the
e-Bee will come in useful in developing a national cadastre and doing
strip surveys along road traces, canals and highways. "We are planning
to do a survey of Badulla town with the UAV - this can expedite most of
the work," he told SciDev.Net.
Siddiqui says that because drones fly below the clouds they have a
clear view of the terrain even in bad weather. "It is an important
advantage in emergencies - heavy rain and cloud cover can make it almost
impossible to use a (satellite-based) earth observing system, to assess
the flood extent or damage."- SciDevNet