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Case study I Applicability of high-frequency airborne GPR system for bathymetric surveys

Integrated Systems
October 3, 2023

In hydrographic surveying, accurate bathymetric data is crucial for understanding water bodies' topography and planning various projects. Bathymetry typically involves measuring the depth of water bodies, which has traditionally been achieved using echo sounders.

However, a recent SPH Engineering and Frontier Precision Unmanned trial introduced an unconventional approach using a Radar Systems Zond Aero 500MHz Ground Penetrating Radar (GPR) for high-resolution airborne bathymetry assessment. This case study presents the operation’s details, challenges, and outcomes.

Challenge

In the presented case, SPH Engineering and Frontier Precision Unmanned aimed to explore the feasibility of using the drone-based 500MHz GPR system for bathymetric surveying. The trial occurred over a pond with limited physical access, where the GPR and the Echo Sounder ECT400 System were tested for bathymetric data collection.

The trial encountered several challenges, including the unconventional choice of using a 500MHz GPR for bathymetry. Typically, low-frequency GPR systems are used for bathymetry. The test assessed the feasibility of using an Integrated System with a high-frequency GPR system.

Methodology

Data Collection: The trial involved two methods: the airborne Echo Sounder system for traditional depth measurements and the GPR system for unconventional bathymetric measurements.

Flight Path: The drone was flown with minimal clearance over the water (30 cm between the GPR antenna and the water surface), allowing the GPR system to capture data from the water column.

Data Processing: GPR data collected using the Zond Aero 500 was processed using Geolitix software. The processed data was then imported into Hydromagic software from Eye4Software B.V. for visualization and comparison with the Echo Sounder data.

GPR data processed and visualized in Geolitix.

Results

Surprisingly, the trial yielded good results. Despite the unconventional choice of GPR for bathymetry, the data collected from the GPR closely matched the depth measurements obtained from the Echo Sounder System. The comparison between the check line data from the Echo sounder and the survey line data from the GPR showed only a few centimeters of difference. This suggests that the GPR, even though not designed for bathymetry, can still provide accurate depth information when used under specific conditions, such as low-conductivity water bodies.

Through this trial, the team developed a workflow for processing GPR bathymetric data with minimal effort. This workflow could pave the way for utilizing GPR in bathymetric assessments under specific circumstances.

Data comparison: GPR vs. Echo Sounder. Green dots are measurements made with GPR; the blue line is the data collected using the Echo sounder.
Depth map generated in Hydromagic software.

Conclusion

The SPH Engineering and Frontier Precision Unmanned trial showcased the innovative use of the GPR system Radar Systems Zond Aero 500 for bathymetric assessment over a pond. Despite the challenges, the results demonstrated that unconventional approaches can yield accurate depth information, especially when combined with advanced flight planning and data processing techniques. While traditional methods like echo sounders remain the standard for bathymetric measurements, this trial suggests that there might be room for exploring alternative technologies in specific scenarios.

Download data set of UAV+GPR system Radar Systems Zond Aero 500 for bathymetry

Datasheet: adar Systems Zond Aero 500 GPR system

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