To begin with, we used our WingtraOne fixed-wing VTOL with a 20MP Sony QX1 camera, to fly a pre-programmed photogrammetry grid over the entire beach.
A spread of ground control points were placed and surveyed using an RTK GNSS system, to ensure the photogrammetry data could be accurately tied (to approx 10 mm) into real-world coordinates.
The imagery and control point data were then processed into a dense point cloud of approximately 70,000,000 colourised points. These were then used to generate a digital surface model, 3D mesh model and othorectified stitched image.
To assist with a beach sand replenishment project, Geo-4D performed onsite aerial topographic mapping and in-situ geotechnical testing, followed by interpretative analysis and reporting
testing and analysis
Geo-4D utilised a dynamic cone penetrometer (DCP) and handheld cone penetration test (hCPT) to characterise ground conditions to approximately 2 m below ground level.
The aerial data were used to guide the siting of the the geotechnical tests, to best characterise the key morphologies and depositional environments at site.
DCPS were positioned in all morphologies, whilst the hCPTs (quicker to perform) were spread out over a wider area to help with any interpolations between DCPs.
The DCP and hCPT data provided an indicative stratigraphy, highlighting potential soft cohesive layers, and to derive bearing capacities to aid in the selection and movements of plant at site. The beach was then divided into geotechnical zones based on stratigraphy, morphology and bearing capacity.