An Extraordinary Adventure in Precision Mapping
Tackling the Dwangwa Floodplain
Picture this striking contrast: cutting-edge drones fitted with sophisticated LiDAR sensors being carried across Lake Malawi in a traditional dugout canoe. This striking image embodies the spirit of an innovative floodplain mapping initiative led by Agri-Sense, utilising OPTRON’s state-of-the-art DJI M350 RTK drone. The project highlights the groundbreaking use of drone technology while showcasing the deep trust and collaboration that has flourished between Agri-Sense and OPTRON over the course of more than ten years.
The genesis of this ambitious project lay in the pressing need to address the flood risks along the Dwangwa River, which feeds the irrigation system of the Dwangwa Sugar Estate (DSE). In the aftermath of a devastating flood that reshaped the river’s path and breached protective dykes, Agri-Sense was commissioned to map the 7500-hectare floodplain.
The Mission: Provide accurate data for a hydrological model to guide the redesign of flood defences.
The project comprised an aerial survey of a vast 10,000-hectare area – which included a 100 m buffer around the area of interest. This was strategically split into six manageable blocks to ensure efficiency and precision. Each block was precisely defined depending on operational logistics and natural boundaries so the team could address the survey in phases. This segmentation streamlined data collection and ensured consistent quality across the project. Through division of the project, overlaps were reduced, and the team could concentrate on keeping a clear focus on producing high-quality outputs for every block in the limited timeframe.
To accomplish this, Agri-Sense deployed a DJI M350 RTK drone equipped with the L2 LiDAR module. In a span of eight days, the drone undertook about 103 flights, which worked out to about 43 hours of flying, meticulously gathering data with a remarkable resolution of 4,2 cm. Reaching an altitude of 150 metres, this astonishing precision marked a pivotal advancement in both efficiency and accuracy in aerial land surveying.
A decade of trust with OPTRON
The success of this project was built on a foundation of trust and collaboration between Agri-Sense and OPTRON. Since 2013, OPTRON has played a pivotal role, providing technology and training that align with Agri-Sense’s changing requirements. The enduring partnership guaranteed that Agri-Sense possessed not only top-tier equipment for the task but also the specialised knowledge to implement it successfully.
“When we look at new projects, OPTRON is always our first call,” said Russell Longhurst, Team Leader for the project. For this project, we collected 21,773 images—165 GB of imagery data—and an additional 273 GB of raw LiDAR data in just 43 hours of flying. That scale of operation simply wouldn’t have been possible without the right equipment and training.”
Why the DJI Matrice 350 RTK drone?
The decision to use the DJI M350 RTK drone stemmed from various considerations, including its payload capacity and compatibility with the L2 LiDAR module.
In contrast to photogrammetry, which is dependent on lighting conditions and often faces challenges with thick vegetation, LiDAR possesses the ability to penetrate foliage, effectively capturing ground points. This capability proved critical in the marshy, reed-laden landscape of the Dwangwa floodplain.
The drone’s efficiency also stood out. With hot-swappable batteries and auto-calibration features, downtime was minimised. During its multiple flights, the drone consistently flew at a height of 150 metres and a speed of 12 metres per second, achieving the sweet spot for both data accuracy and battery efficiency.
Two teams were deployed to tackle the massive 7,500-hectare floodplain, each playing a critical role. The Ground Survey Team, led by Russell Longhurst, was tasked with prepping the area by installing Ground Control Points (GCPs), measuring water levels, and doing pre-survey inspections. Equipped with motorbikes, they navigated dense bush, swampy fields, and limited road access, working furiously for 10 days to prepare the region for aerial operations.
Nick Bradley led the Aerial Survey Team, which deployed the DJI M350 RTK drone. They conducted the aerial survey deploying six strategically placed drone base stations around the floodplain, using modern LiDAR sensors and RTK corrections to capture high-resolution data, ensuring seamless coordination and precise results.
Navigating logistical challenges – creatively
The technical feats of this project were matched only by its logistical challenges. At the forefront of these efforts was the transportation of lithium batteries into Malawi. Due to airline restrictions on lithium batteries of this size, the team couldn’t bring them on passenger flights. Instead, the batteries were dispatched in advance via bus, with a dedicated courier ensuring their safe passage. “It took a week to get the batteries to Malawi,” Longhurst explained. “Without them, we couldn’t start our project. However, the time was not wholly lost because OPTRON provided us with temporary substitutes, and we used the time well by attending drone training, guaranteeing no time was wasted.”
Accessing remote areas required creative problem-solving. While motorbikes maneuvered through the treacherous muddy floodplains, certain areas proved so inaccessible that the team had no choice but to use a dugout canoe to ferry their 100-thousand-dollar equipment across the vast expanse of Lake Malawi. A wooden boat, equipped with a modest five-horsepower engine was gingerly loaded with generators, drones, survey kits and personnel.
“It was surreal,” Longhurst recalled. “We were operating high-tech drones under a tree on the lakeshore, charging batteries with a generator while trying to stay cool in the intense heat.”
Additionally, in response to the challenging terrain and to ensure safe drone operations, the team crafted innovative take-off and landing pads from materials readily available in the area. Given the impracticality of traditional rigid platforms caused by transportation constraints, the team chose to utilise durable, lightweight blankets that were inexpensive and locally sourced, fastening them to the ground with roofing nails.
The makeshift pads provided a stable, dust-free surface for the drones, minimising wear and tear on the equipment.
“It was a simple but effective solution,” Longhurst explained. “We needed something portable that could handle the harsh, uneven ground, and these blankets worked perfectly.” This approach not only simplified logistics but also exemplified the team’s resourcefulness in tackling field challenges. “Over eight days, we mapped over 10,000 hectares with 43 hours of flight time. It’s a testament to both our technology and our team’s resourcefulness,” he observed.
Transforming surveying efficiency
The introduction of the DJI M350 RTK has transformed Agri-Sense’s operations. The drone’s user-friendly interface and meticulously designed pre-planned flight paths enabled the team to operate with remarkable efficiency, accomplishing a project of this magnitude in slightly more than a week. The introduction of hot-swappable batteries and automated calibration transformed the workflow, leading to significant savings in both time and cost.
“Every small feature added up,” said Nick Bradley. “From faster setup times to efficient battery management, the drone allowed us to maximise productivity. The fact that we captured 273 GB of LiDAR data and maintained 100% operational uptime speaks volumes about the efficiency of this equipment.”
Agri-Sense sees immense potential for the application of drone technology within the realm of agriculture, extending far beyond this project. LiDAR’s ability to map through dense crops like sugarcane opens new possibilities for irrigation planning and crop monitoring. As Longhurst put it, “We can now map fields without waiting for harvest, which saves time and enhances data accuracy.” In this project, the LiDAR technology successfully captured ground points, even amidst the thick growth of reeds and sugarcane—a remarkable achievement that traditional photogrammetry would have been unable to accomplish.
The ever-important human element
The human element was just as crucial even if technology took front stage. Whether it was negotiating the wilderness or erecting drone base stations in challenging areas, the team’s flexibility and problem-solving aptitude guaranteed the success of the project.
“Our client-centric approach is the key to our success,” reflected Longhurst. “By understanding the end goal and working backward from the client’s needs, we ensure every step, from survey to final deliverable, aligns with their objectives. This focus not only sets us apart but also enables us to complete projects like a 10,000-hectare survey in just eight days without compromising on quality.”
Apart from offering a narrative of perseverance, inventiveness, and cooperation, this project highlights the many opportunities of drone technology. From the absurdity of moving high-tech equipment in a dugout canoe to the accuracy of mapping down to millimetres, this story underlines the transforming potential of merging modern technologies with human creativity.
As the floodplains of Dwangwa are brought into sharper focus, Agri-Sense and OPTRON are relentlessly advancing the limits of innovation, establishing a new benchmark for surveying and agricultural mapping. This adventure in Malawi is not just a technical achievement, it stands as a tribute to the lasting strength of collaboration and the essence of discovery.
– Kim Kemp
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