UAS photogrammetry surveys have the capacity to map 100+ hectares in a single day, providing a highly effective and efficient method for mapping landscapes.
This technique can complement large-scale topographic surveys ahead of new developments, produce a base map for commercial projects, and identify subtle earthworks with archaeological potential.
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How does it work?
Ground control points are established around the site and recorded to OS coordinates with a GPS. Following this, a UAS with a gimbal-mounted camera is flown in an automated grid over the site, capturing photos at regular intervals from an altitude between 50 and 120m. The photos are processed using photogrammetry software to produce a georeferenced orthophoto with a ground sampling distance of between 1 and 3 cm/pixel, and a Digital Elevation Model (DEM). The georeferencing aims to be within an error of 5cm, though is typically below 3cm.
Additionally, a 3D model of the landscape can be produced for general visualisation, and may assist with the planning of a project.
Above: DEM of a 300 hectare landscape survey.
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Additional Outputs
Traditional Topographic Survey
A high-density point cloud can be exported and combined with terrestrial data, providing topographical information across wide landscapes. The combined outputs can be drawn up in CAD.
Archaeological/Earthwork Report
The DEM can be analysed using GIS to tease out micro-topographic features which can be discussed in an interpretive report.
Above: CAD drawing combining UAS and land topographic surveys (left), and an archaeological interpretive report (right).
Above: Orthophoto of a 110 hectare landscape survey.