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Surveying a private island with Reach

3DroneMapping is offering mapping services all over the Africa and recently had the privilege of mapping a tiny private island in the Indian ocean just 9 km off the Zanzibar coast.  Luke Wijnberg, surveyor and CEO of 3DroneMapping shared a great story about the resort and its mapping with the Reach modules.

The tiny (15ha) island is approximately 5NM (9KM) from the mainland is completely isolated from the rest of the world. Surrounded by live coral reefs and sand bars, the island is home to an exclusive, high-end resort. The resort prides itself in being completely self-reliant and offers guests individual service that would rival some of the best hotels. The island limits it number of guests to 20 to maintain the feeling of being remote and disconnected from the world.

The island has limited space as it stands and is now in threat of it shrinking further. As currents have changed, part of the island is eroding at a very fast pace, So much so that the developers are concerned that some of the newly proposed structures will be wash out to sea in a few years. Since no plans or maps of the island have ever been drawn or surveyed, they felt it was important to give some scale and dimensions to the architects for the master plan.

The plan of the island was to include all existing structures, pathways, major trees, visible services, high tide marks, levels and contours. This needed to be done in a very tight timespan as the island closed for renovations in 3 months. Another major concern was that the survey could not disturb any guests while being carried out.

Using a multirotor drone with high resolution camera allowed us to operate high enough to still obtain images with good detail but far away enough from guests to not bother them. Total time for the flights was 30min, also reducing the time spent flying over paying residents. Control points were placed over the island at strategic places to not be visible to the public but in a fashion that met basic survey principles. The GPS used for the control points was the tiny L1 Reach.

Units have proved themselves over and over to be some of the cheapest and accurate single frequency receivers about and are perfectly suited to this type of survey.

After fieldwork, the photogrammetric process was a fairly simple affair with 600 images collected and control added to the model. A high over and sidelap was required to obtain ground strikes between the vegetation. The ground strikes where then extracted from the dense pointcloud using specialized 3d pointcloud editing and classification software. These were fairly easy to identify given the flat nature of the terrain on the island. Within a 3d viewer and GIS environment, the other required features were also extracted and exported directly to a CAD.

All files were handed to the client via an online GIS platform as well as AutoCAD files for the master planners to work with.

Such a survey could not have been possible without drones and Reach kit. Using this technology kept the pricing low for the customer, allowed 3Dronemapping to obtain additional byproducts for the delivery such as orthomsoiacs and pointclouds for rendering, kept time on the ground and disturbance to guests to a minimum and provided a very quick turnabout time.