Sri Lanka's drone pioneers

In recent months, the Colombo based International Water Management Institute (IWMI) has begun to use unmanned aerial vehicles (UAVs) – also known as drones – to monitor rice crops in and around the water scarce area of Anuradhapura. The institute is testing the data-collecting capabilities of UAVs for various purposes. For example, RGB (red, green, blue) colour and near-infrared (NIR) sensors were used to capture images over the paddy fields. These technologies have the potential to help farmers detect fields that are under stress and to help them identify low-laying areas prone to pooling.

IWMI's drone is also regularly used in partnership with local authorities. In December 2015, the Survey Department of Sri Lanka was developing a disaster mitigation plan for Badulla, the capital city of Uva Province. The Survey Department needed a high-resolution Digital Elevation Model (DEM) of the town for the plan, and asked IWMI to use its drone to capture the required aerial imagery.

Using conventional techniques, it might have taken over a year to survey the town. However, the drone used by the IWMI team was able to survey the entire 10 square kilometres area in just three days, by carrying out fourteen UAV flights and shooting 4,600 high-resolution images, with an average spatial resolution of four centimetres.

Disease prevention

Drone imagery can also be used to better understand the spread of disease, allowing health analysts to create high-quality maps. Chronic Kidney Disease of Uncertain Aetiology (CKDu) is one of the most serious non-communicable diseases presently afflicting Sri Lankans, and it remains poorly understood. First diagnosed in the mid-1990s, the disease has now been found to occur in six out of the nine Sri Lankan provinces. It is essentially confined to the dry zone and only affects farmers engaged in rice cultivation. CKDu is believed to have resulted in the death of approximately 25 thousand people to date, while over 8 thousand people are currently estimated to be receiving treatment for the condition.

In the CKDu-affected area of Mahiyangana, the disease is believed to be spread via contaminated drinking water, which originates from wells. The UAV has been used to gather geo-referenced data on where households live and where wells are located. The collected data can be used in addition to a digital elevation model to locate the high and low areas of two villages, Sara Bhoomi and Badulupura.

The gathered data has been used in support of a pilot project on prevention of CKDu in the area. According to project leader Ranjith Mulleriyawa, these aerial photos and maps have provided researchers with an improved overall picture of the area, helping them understand how contaminated wells are linked to the spread of CKDu in affected areas.

High accuracy

IWMI also plans drone initiatives in Nepal to map fresh water springs by using a small thermal sensor. The targeted watersheds in Nepal have dense canopy cover, and it is difficult to use standard optical sensors to identify and locate the springs. The drone-mounted thermal sensor can see through the dense canopy cover to find these springs, as their temperature is lower than the temperature of the earth surrounding them.

While the use of UAVs in research and other practical applications remains in its infancy, IWMI’s initial tests have already demonstrated their usefulness. Drones can be used to carry out surveys over large and hard-to-access areas, in a relatively short timeframe and with high accuracy. For policy experts and decision-makers, these aerial images can provide them with more accurate and up-to-date information than has hitherto been possible. For farmers, high-quality drone images can help them detect potential crop failure early, giving them enough time to respond.

IWMI thinks that UAV based surveys will be especially useful in studies that require highly accurate and repeated monitoring. These include checking for changes in cropping patterns, shifts in the status of important water resources, and documenting the extent of environmental disasters. It doubtless won't be long before farmers routinely use UAVs to monitor their crops, just as they use more conventional machinery to sow and harvest. 

Related links

Website of the International Water Management Institute.
http://www.iwmi.cgiar.org