3DroneMapping was appointed as consultants to undertake an aerial survey of a potential lithium mine site in southern Mali. The project comprised a total surface area of approximately 18 000 hectares. The client requested orthomosaics and DTM products be produced.

Control points were placed around the site. These were surveyed to within 20mm accuracy with survey-grade GPS. As RTK was not an option due to long baselines, post-processing of raw GNSS measurements was done.

Flight operations took 3 days with an average of 3 flights per day due to restricted access to electricity. a total of 850km was flown in very challenging conditions. Daily temperatures often exceeded 40°C and winds were in excess of 14m/s.

drone flight plan, Mali

Post processing of trajectories gave excellent results from the INS system. All values were within tolerance. Target images were referenced in XYZ and OPK ready for photogrammetric routines.

Photogrammetry was relatively straight forward and standard outputs exported. Minor manual classification of DTM was required as most artifacts could be separated via automated algorithms. Processing was completed in 72 hours

drone aerial survey DTM in Mali

DTM, orthomosaic and contours were generated as final outputs.

Drone contours
drone orthophoto

This was a fairly simple survey done in challenging environmental conditions. The main reason for the missions success was careful planning and maintaining efficiency in the field.

Aerial survey drone in Mali

For our oldest aerial survey drone, this was its last mission as it will be retired. The aircraft has done incredibly well over the past few years, flying many thousands of kilometres. It has collected mud from over 12 different countries on its skid plate and is functioning perfectly.

However, it is now time to bid it adieu as we usher in a new era of photogrammetric sensors, more flight time and ease of operation.

By Luke Wijnberg

CEO / FLIGHT OPS at 3DroneMapping | Working as a surveyor for the past 15 years in both the aerial and land surveying industry, Luke has amassed a deep understanding of the applications of RPAS mapping and its role in conventional surveying. Luke has operated drones all over the African continent and has flown a variety of missions with both fixed wing and multirotor RPAS.