Topographic Surveys Using UAV:

Mott MacDonald Bentley

Topographic surveys are widely used across the civil engineering and construction industries – on sites where it’s important to get a clear understanding of shape and contour. However, the traditional approach – using teams of surveyors to locate hundreds or thousands of points on a chart – presents a number of challenges that modern UAVs can address.

Site access is a common obstacle to the speedy completion of a survey. Those visiting a site may have to contend with restricted vehicular access, physical barriers such as fencing and hedges, landowner permissions and even hazards such as deep mud or steep slopes. By contrast, a UAV can make repeated passes over a site without obstruction, enabling surveys to be completed many times faster than the usual manual approach.

Modern software can be used in conjunction with high resolution photography to generate a detailed 3D model with accurate contour mapping. Importantly, these contours are based not a few thousand individually measured points but millions. The resulting model delivers far more detail than any conventionally produced drawing and, when the original photos are set as a separate layer beneath it, the result provides engineers and planners with additional visual cues, context and a clearer understanding of any uncharted features.

Typically, the UAV survey process will be in the region of four times faster than a manual survey and will yield corresponding cost savings. However, ground conditions will largely dictate the speed and, in some circumstances, projects may be completed up to ten times more quickly.

However, UAV-based surveys cannot and should not be conducted completely independently from a surveyor. On a middle-sized site, perhaps a dozen control points will need to be located and marked on the ground for reference. Obviously, however, setting just twelve points rather than thousands represents a significant time saving and quickly frees survey staff to move on to other work.

SUAVE has recently undertaken topographic surveys of the terrain surrounding a reservoir and, separately, an area around a broken water main. With subsequent processing, which SUAVE can deliver, the survey data from projects such as these can be plugged into client systems to provide an accurate digital record of the site. For more information about topographic surveys, please contact us.

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