Drone photogrammetry: 3D surveys with centimetre accuracy

A traditional topographic survey is slow, expensive and samples the ground point by point. Drone photogrammetry measures all of it: every square metre of the site becomes a navigable 3D model, accurate to the centimetre. Here is how it works and when it pays off.

// Point cloud + contour lines: every surface of the site measured, not estimated.

01How aerial photogrammetry works

The drone flies a programmed "lawnmower" route over the site, taking hundreds or thousands of photos with roughly 80% overlap between frames. Each shot is georeferenced with centimetre-corrected RTK GPS. Photogrammetry software recognises the same points across multiple images and — by triangulation — reconstructs their position in space.

The result is four products, all generated from the same flight:

• Orthophoto — an aerial photograph corrected geometrically, measurable like a map.
• Point cloud — millions of XYZ points describing every surface of the site.
• Digital terrain/surface model (DTM/DSM) — elevations, slopes, sections and contour lines.
• Textured 3D mesh — the navigable digital twin of the site or the building.

02Drone versus traditional surveying

A survey crew with a total station or GPS samples dozens of points an hour, choosing where to measure. The drone captures the entire surface: on a 40-hectare site, a 20–30 minute flight replaces days of ground work, and the data is not a sample but a census. Site-access preparation — often the longest part of a survey in difficult areas — drops by up to 90%.

The advantage grows where the ground is hostile: embankments, industrial roofs, quarries, unstable areas or live plants that cannot be shut down. The drone measures without anyone setting foot where it is dangerous or forbidden.

03What it is used for, in practice

• Solar design — terrain model for tracker layout, shading analysis, earthworks calculation.
• Construction sites — periodic progress states, cut-and-fill volumes, documented works accounting.
• Engineering & structures — inspection of roofs, façades and infrastructure with measurable models.
• Agriculture — vigour maps, drainage, irrigation planning on real elevation data.
• Before/after — comparison between successive flights: every change in volume or elevation is measured, not estimated.

04What we deliver

High-resolution orthophoto, classified point cloud, DTM/DSM and 3D mesh in standard formats (GeoTIFF, LAS/LAZ, OBJ, DXF), ready for QGIS, AutoCAD, Civil 3D or whatever platform you already use. Every delivery includes the accuracy report with residuals on the control points: the data is verifiable, not to be taken on trust.

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