xyHt | GPR on a Drone
Article by Alexey Dobrovolskiy.
An international research team used new UAV and GPR technology to locate a lost U.S. airplane 300 feet below the ice in Greenland.
On July 4, 2018, at Greenland’s Ice Cap, Jim Salazar and Ken McBride from Arctic Hotpoint Solutions and the Fallen American MIA Repatriation Foundation (FAMIARF) located the P-38 “Echo,” a U.S. dogfighter lost during the events of WWII. A subsequent hydraulic oil probe confirmed the plane’s location, bringing this part of a long mission to a gleeful close.
The mission’s success can be attributed to two factors: testing new unmanned-aerial-vehicle (UAV) and ground-penetrating radar (GPR) research technology and a team of skilled experts. Jim and Ken were joined by U.S.-based specialists Mario Carnevale and Myles Danforth from Hager GeoScience Inc., Latvian UAV expert Jãnis Kuze, and me (Alexey Dobrovolskiy, CTO of SPH Engineering).
Jim contacted SPH Engineering to join the search back in 2017. During this mission, our team battled Greenland’s snowstorms, low temperatures, near-blinding Arctic sun, no internet, and technical difficulties in order to locate the lost airplane and set it in motion bringing it home.
Locating “Echo”
For the eight-day expedition on Greenland’s Ice Cap, the team worked in two groups: the UAV group and the land survey group. The UAV team began their research with new technology, a GPR and a drone integrated system, to locate the P-38.
The UAV radar’s contact was confirmed by the ground surveying group—acquired data showed anomalies at a depth of around 300-340 feet. The distance between the determined locations of both groups was 10 feet, and the drilling location was calculated based on joint surveying data.
The moment of success for the expedition came in the form of a red fluid extracted from a depth of 340 feet, identified as the hydraulic fluid used in U.S. aviation.
Experience gathered during the expedition confirmed the applicability of modern technologies to search and locate deep targets buried under glacial ice.
“We are confident that this innovative technology will assist our upcoming projects with the search of the USCG J2F Duck [with three fallen veterans] in the 2019 expedition,” said Salazar, director and founder of the FAMIARF.
The overall results were promising and proved that the performance of aerial surveying is ten times more effective compared to ground surveying and less risky for ground operators. Furthermore, putting our drones to the test in the harsh environment highlighted some equipment’s inability to function as expected, which is invaluable knowledge for future expeditions.
Arctic Hot Point Solutions is now organizing the excavation of the found P-38 Echo (to be conducted in 2019) and is continuing its search for other U.S. aircraft lost in Greenland.
GPR and Drone Integration
Due to Greenland’s hostile weather conditions, radar search was limited, and ground operations needed to be executed quickly and precisely. This is where our extensive unmanned-system-integration and software-development expertise was required; at SPH Engineering, we fly and test all things drones, small planes, and helicopters at our air-field on a daily basis.
GPR/drone Benefits
Significant benefits of GPR/drone integration are varied. First, a drone is independently flown across the terrain with constant speed, improving fieldwork productivity tenfold.
Second, drones follow survey lines precisely. While it’s common to mark a survey area using flags or ropes, a drone can automatically follow pre-programmed routes with extreme height precision. Mounting a standard GPS receiver on the drone will provide the precision of approximately 3-4 meters, whereas using an RTK GPS will improve precision by mere centimeters. Additionally, an RTK receiver only increases drone-related expenditures by a few hundred dollars. A drone also remains at a constant speed, which can be crucial for continuous data-recording sessions; what is almost impossible to achieve using standard equipment is almost a free drone benefit. The last perk of using drones is as crucial as it is obvious: safety. In some cases, like our glacier mission, walking on the surface can be extremely dangerous. A drone operator is able to remotely monitor flight and GPR operations from a safe distance.
Our Custom System Putting together a GPR drone for missions such as Jim’s isn’t easy, but it’s not rocket science either. You need to fix a light GPR antenna under a drone and use a standard tabled computer (also fixed somewhere) to record data.
Although such a system will work in ideal conditions, you still need an integrated system to reap the real benefits. A fully integrated GPR/drone, like the one we used for the mission, has the following features:
- GPR data is recorded onboard using specialized data-acquisition software that will not require the operator’s intervention to start/stop logging and can work robustly in unattended mode.
- GPR data is geotagged using GPS coordinates (every trace is recorded together with coordinates).
- If the drone is equipped with RTK GPS, precise coordinates should be used to geotag data.
- The drone operator is able to control GPR from the ground: start/stop data recording, change GPR mode and settings, etc.
- The drone operator should be able to see how GPR works or at least see current trace data.
