Case study by SPH Engineering · Ground Penetrating Radar · Construction
Checking a retaining wall's depth with drone-based GPR
A company building a new residential area needed to confirm that its retaining walls were built to the design depth. Measuring that on a near-vertical wall is hard, so it used the RadSys Zond Aero LF drone-based ground penetrating radar, integrated by SPH Engineering.
The challenge
Retaining walls must be built to the correct depth and to the design specification. Checking that during or after construction is difficult, especially when the walls are nearly vertical. Digging to check is slow and can damage the work.
The solution
The developer flew a RadSys Zond Aero LF ground penetrating radar on a DJI M300 RTK with the SkyHub onboard computer. The drone collected radar profiles spread evenly over the height and length of the walls, even in difficult flying conditions. The 300 MHz channel gave enough penetration to map the wall depth at heights of up to 8 m.
The data was then processed in RadSys Prism2 software to produce the radargram profiles.
The result
The interpretation showed that the retaining wall had been built to its design specification: a 3.6 m block depth and 1.2 m height. The developer got an as-built check of the wall's structural elements at both the top and the base, without excavation.
SPH Engineering lists these benefits of drone-based GPR in construction:
- accurate, detailed data on underground structures and utilities, reducing the risk of excavation mistakes;
- a non-destructive way to confirm subsurface as-built compliance;
- better safety, because crews do not have to work on uneven or dangerous surfaces;
- less time and cost than traditional site surveys, with automated data collection.
Where this applies in India
The same as-built checks are useful wherever structures are hard to reach on foot:
- retaining walls on highway, expressway and railway cuttings;
- hill-road and slope protection works;
- embankments, abutments and walls on large township and industrial projects;
- pre-handover quality checks for contractors and consultants.
SPH Engineering's GPR training is also available through HobiTech.
The equipment, available from HobiTech
| Ground penetrating radar | RadSys Zond Aero LF |
| Onboard computer | SkyHub by SPH Engineering with the SkyHub GPR software |
| Drone | DJI M300 RTK was used in this project. Ask us for current compatible drones. |
| Processing | RadSys Prism2 |
Case study by SPH Engineering, published May 2023. This page summarises it in our own words; the survey was carried out by the developer, not by HobiTech. Read the original case study on SPH Engineering ↗
Need to check what is under the surface?
Tell us the structure, the depth you need and the site conditions. We will recommend the GPR, drone, SkyHub and software, quoted in rupees with a GST invoice.