Drones And Ground Penetrating Radar: Drones For Good
While much has been written about the danger drones pose for planes when they are flown negligently, there are actually a number of positive uses for UAVs in relation to aircraft. Let’s take a look at how one drone and ground penetrating radar helped to uncover a plane lost at sea.
In this article you will learn;
- What is the lost squadron
- What is Ground Penetrating Radar
- Equipping drones with GPR
- The benefits of GPR over ground surveys
The Lost Squadron of WWII
During World War II, a group of eight planes from the US were lost in Greenland. Nicknamed the ‘Lost Squadron’, allied planes would often fly what was known as the Snowball Route, hopping between a chain of top-secret bases in Greenland and Iceland before arriving in the UK. However, the Lost Squadron crash-landed on a glacier after being driven out of the sky by a snowstorm, and over the years became buried under layers of ice.
Fast forward more than 70 years, and a search team headed up by California businessman Jim Salazar found one of the wrecked P-38 jets in July 2018. Using a ground-penetrating radar fitted to an aerial drone, they were able to locate the P-38 more than 91 metres below the glacier. Once they were confident of its location, they used a thermal probe to melt through the ice, which came up covered in hydraulic oil from the aircraft.
Jim Salazar led a team to the Greenland glacier in search of the missing planes every summer for seven years before the P-38 was discovered. Knowing that the key to finding the aircraft was ground-penetrating radar technology, they initially began their search on sledges, but this proved to be slow and dangerous work. Not only did they have to keep an eye out for polar bears, but they also had to avoid ice crevasses, which can swallow up equipment and people. Due to these risks, they decided to look for an alternative way to transport the radar, eventually settling on drones, which led to a breakthrough.
In the year leading up to the P-38’s discovery, the team began using a modified DJI M600 drone. Upon arriving at the glacier, Salazar said that the radar-equipped drone located the plane beneath the ice in a matter of minutes – to put this into perspective, it would have taken the ground crew 6-7 hours to cover the same area with a sledge. This also allowed the search team, which was made up of Salazar and Mcbride as well as Mario Carnevale, Myles Danforth, Janis Kuze and Alexey Dobrovolskiy, to stay sheltered.
The DJI M600
The M600 is DJI’s self-proclaimed first heavy lifter and is designed with six rotors for extra stability and redundancy. Capable of carrying a standard payload of 13.2 lbs (before modification), it has an A3 flight control system, which is ideal for demanding applications where customisation is essential. The A3 flight controller also has built-in measures for low power, loss of signal and propulsion failure (up to three motors). In the event the propellors fail, the A3 automatically switches to Home-lock to help land the aircraft safely.
Ready to use and set up in minutes, the DJI M600 is designed for easy maintenance and maximum durability. As well as foldable carbon fibre arms, it’s equipped with manually-retractable landing gear and has an aluminium body. Thanks to its large propellers and motors, the M600 can stay quiet in the air even while lifting heavy payloads. In terms of cruising, the drone is incredibly agile despite its size. It can fly at a maximum altitude of 2500 metres above sea level and has a maximum speed of 64.8 kilometres per hour.
All of these features made the DJI M600 the perfect choice for Salazar and his team. With a ground-penetrating radar onboard, the DJI is a formidable machine for the exploration of wreckages at sea.
SPH Engineering’s ground-penetrating radar
The ground-penetrating radar system used by Salazar’s team was developed by SPH Engineering.
During the search, SPH’s GPR technology collected data automatically, while the status of the flight and radar was monitored using ground control software (UgCS).
To fully integrate their GPR device with the DJI M600, engineers at SPH developed an onboard computer. The onboard computer replaces a tablet which is commonly used together with GPR but weighs 700 grams less. Thanks to its lighter weight, the drone’s flight time increased by 5 minutes.
As soon as the drone takes off, the radar’s data is recorded. Not only can the system be used for general surveying purposes, but it can also map underground infrastructure and measure the depth of water in oceans, lakes, and seas.
The expedition was highly effective, proving that GPR-drone systems are efficient at locating objects under deep ice and can be used even in unfavourable conditions. Not only does the GPR-drone system save effort and time, but it can also be used successfully in unsafe locations.
Has the P-38 been recovered?
Although Salazar’s team uncovered the location of the missing P-38, also known as Echo, extracting the aircraft from its position will be a challenging task. In July 2020, two years on from the team’s discovery, it’s not known whether Echo has been recovered yet.
Researchers will need to use large, heated plates to melt through 300-feet of ice and tunnel through to the plane. Upon reaching Echo, they will blast the area with hot water, creating a hole large enough to deconstruct it. By removing it piece by piece, Salazar hopes to be able to rebuild it.
With the success of Echo, Salazar now wants to use drones equipped with ground-penetrating radars to uncover more aircraft, including a U.S. Coast Guard plane. The wreck of the Grumman J2F-4 amphibious “Duck” aircraft crashed on the same glacier in November 1942, just months after the Echo went down.
The Duck was part of a search effort for the crew of a C-53 Skytrooper aircraft, which also crash-landed on the glacier in bad weather. The bodies of the C-53 crew, as well as the three men on the Duck, were never recovered despite a multi-million dollar operation. The U.S. government’s DPAA agency announced in 2013 that it had found the crash site of the Duck, but this turned out to be false.
Salazar’s team planned to go back to Greenland in 2019 to work on recovering the P-38 and search for the wreckages of the Duck and the C-53. In July 2018, Salazar told reporters he hoped to “repatriate these men”.
Unexpected challenges of the expedition
Although the expedition was a success, the team did encounter some unexpected hurdles along the way.
Greenland’s summer temperature doesn’t typically exceed 10°C, but because the camp was located approximately 700m above sea level, it was often warm during the day. Except for 3 days of snowstorms, the team was not exposed to overly harsh temperatures. However, these conditions did impact their equipment.
Drone batteries are meant to be kept in warm conditions, forcing Salazar to sleep with the M600’s batteries in his sleeping bag. Additionally, with light coming from all directions on the ice cap, nothing was visible on the team’s screens outside, even when the sun was behind clouds.
The continued use of a GPR-drone can result in issues with low-altitude flights. While standard drones use barometric sensors for altitude measurement, the rapidly changing temperature in Greenland meant measured altitude drops could change by 3-4 metres in a single flight. To prevent the DJI M600 from colliding with the glacier, the team had to regularly stop their missions in the beginning. To overcome this, a high-precision ultrasonic/laser sensor was used to maintain a constant surface altitude, ensuring quality data collection and safe flights.
As well as technical difficulties, low temperatures, snowstorms and the near-blinding Arctic sun, the team also had no internet, so it’s safe to say they had to overcome a number of hurdles to locate the lost P-38.
Why use GPR with drones?
As highlighted above, the research team used a GPR-drone integrated system to locate the P-38 under ice, but what else can it do? As well as seeing through the surface of the ground, it can penetrate rocks and freshwater, providing an additional solution for more efficient surveying.
If you’re wondering if GPR-drones could benefit your line of work, take a look at the range of benefits this technology offers below.
• Time-efficient: Compared to traditional surveying methods, you can acquire data much faster.
• Precision: GPR-drones offer provide accurate measurements thanks to their precise rangefinder and positioning systems.
• Cost-efficient: Compared to manned flights, UAV surveys are more cost-effective.
• Accessibility: Locations which are not reachable by foot, such as ice and water, can be surveyed by drones instead.
• Safety: GPR-drones are ideal in hazardous or unsafe environments and don’t compromise the safety of your staff.
• Automated flights: Thanks to automated flight mode and an in-built GPS, the drone ensures higher accuracy when following survey lines.
The team’s GPR-drone also had the following features:
• Specialised data-acquisition software – data was recorded onboard and didn’t require intervention from an operator to start logging.
• GPS coordinates to geotag GPR data
• Operators could control the GPR from the ground, changing its settings, mode and data recording if required.
• Operators were able to see how the GPR was working as well as current trace data.
A closer look at the applications of GPR-drones
GPR-drones are able to measure the depth of freshwater lakes, rivers and ponds that are up to 15 metres deep. Compared to bathymetry using a board, a GPR-drone offers better accuracy and can deliver equipment to a desired area safely. There is even a possibility to measure the depth of freshwater even when the surface is frozen or partially covered by ice.
Underground infrastructure mapping
On construction sites, underground infrastructure mapping is a vital task to check land which has previously been developed for any potential problems. It’s also useful when maps or documentation for an underground structure are missing.
Before any construction work begins, GPR-drones can help assess an area of land. As well as finding any potentially dangerous leaks or water streams, drones can help ensure safer working conditions and higher productivity where there is rough terrain.
A GPR-drone which is flown as low as possible can help mimic the relief of a surface, including depressions and elevations valleys, peaks, and plateaus.
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Ultimately, the overall results of Salazar’s mission are promising for the future of drones and ground-penetrating radar technology. As well as proving that, when compared to ground surveying, the performance of aerial surveying is ten times more effective, it also has a number of health and safety benefits which simply can’t be ignored. Furthermore, putting the DJI M600 to the test in a harsh environment provided invaluable knowledge for future expeditions.
To find out more about DJI drones and their application in a range of environments and projects, contact us here.