Sierra Leone aerial survey with a drone

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Dutch Engineering and Consultancy company Witteveen+Bos carried out a feasibility study for the small-scale generation of hydroelectricity in Sierra Leone at the request of the local company Multi Experience. The aim of the study was to see if the power of the water from small rivers could be used for the generation of electricity that could be input into the national power grid. A part of this feasibility study was the survey of six potential locations each averaging around 12km2 each. In total Skeye surveyed approximately 70 km2.

The Trimble UX5-HP fixed wing drone was used for this aerial topographic survey. The drone is equipped with a high-resolution photo camera and images are taken in a pre-programmed manner so as to create sufficient overlap between the images. In the overlaps the terrain heights can be computed using photogrammetry techniques. Terrain heights can be extracted as dense as 100 points per m2 and these are used as an input to create a 3D digital terrain model.

The team on the ground consisted of one Skeye pilot/surveyor assisted by a two man team from Multi Experience. This company assisted Skeye in obtaining all the required local permissions for this project and future planned projects.

The use of a UAV to carry out the aerial topographic surveys is new to Witteveen+Bos. In the past similar areas were surveyed with traditional methods whereby a land surveyor would measure cross profiles of the terrain with an interval of 100 meters. For one single location the time required to do so would be between a week and ten days. With the use of a UAV this was brought down to just one single day.