Sonar surveying the floor of a flooded quarry
Usually, you will find us below ground scanning or climbing through to the next cavern with a huge amount of scanning equipment, not carrying out SONAR surveying from the back of a boat in winter. This morning we set out to map the floor basin of Capernwray, a former quarry, now flooded and used as a dive centre. The reason for this early start and rubber dingy journey is to test out a new sonar rig to ascertain if it’s going to deliver the results we need for upcoming bathymetric surveys of several tropical rivers.
The rig loaded and ready for use today is the StarFish 452F; for those of you who are technically inclined, the starfish is is a high-frequency side-imagining, sonar device. The starfish is an unusual design with hydrodynamic three fins, it differs greatly from the common cylindrical torpedo shape side scan of many sonars.
With the StarFish – 452F loaded safely and attached to a rope of 10m, we set off across the quarry lake to test the range and resolution capabilities of the imaging device, which promised us wide range imaging of 100m per channel, which is 200m total swathe coverage.
The surveying process
The sonar surveying took us approximately 20 minutes, with a distance of 0.5 km. With the data safely gathered we rushed back with the data to see what this compressed high-intensity radar pulsing bit of kit could deliver, and would it be enough? Safely back in the office, we launched the data and saw some very convincing and highly detailed scans produced. Overall, we were indeed happy with the Starfish side scanner, which had picked up several artifacts in the lake including a sunken plane.
The detailing of the plane wasn’t high resolution, but the floor of the lake and side facings were captured in full quality, which is exactly what we need from the Starfish. We are now working on programming methods to turn this data into a 3D image of the lake floor.
View the video below to find out a little more about the process: