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Why are ground surveys still needed under forest canopies?

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surveying Figure 1: Photogrammetric photographs from two short, overlapping flight strips arranged for supplying mapping details. Photo-control points are shown on only one photograph; shading indicates a typical terrain feature such as a lake (see text).

Ground surveys remain essential under forest canopies because they allow engineers to determine the precise shape of the ground surface itself, rather than the profile of the treetops or vegetation cover.1

While remote sensing technologies like lidar can penetrate vegetation to map surface features, ground-based surveying is still required for specific engineering needs where high precision is critical. This is particularly important for projects requiring accurate height determinations, such as planning railway gradients or designing irrigation and drainage networks, where even minor errors in elevation can significantly impact the functionality of the infrastructure.21

Additionally, ground surveys are necessary when features are not easily identifiable via aerial methods, such as defining specific property boundaries or identifying transition zones between different soil or vegetation types. In these instances, the manual, point-to-point measurements of a ground survey provide the necessary accuracy that automated aerial techniques may not achieve.1