UAV photogrammetry to support rehabilitation works of heritage buildings

 

The mapping and measurements of existing heritage infrastructures typically present many logistical challenges. A large number of undercuts, restricted spaces, fully or partly modified structures, as well as uneven, misaligned, and distorted elements, can give headaches to surveying professionals. Luckily for them, one new technology developed recently is presenting interesting solutions for the measuring of buildings.

Unmanned Aerial Vehicle (UAV) – commonly known as “drones” – allow the precise and accurate (millimeter exact) surveying of exterior façade elements. Aerial photogrammetry techniques combined with UAV gears implies that the flying device, equipped with high-quality cameras, takes series of pictures of the object to be measured and generates a rich and dense point cloud 3D model from the pictures recorded using triangulation principle.

This point cloud model can be furthermore transformed either into a so-called “Orthophoto” (one overall, scaled, highly realistic 2D picture of the whole object, made out from the merging of all images recorded), into a “Mesh” surface (2D vector representation of the object similar to traditional CAD models) or even into 3D Model compatible with BIM software. The set of data points resulting from the survey offers flexible solutions suitable for further potential uses of the information within a digital CAD model, and that, according to the specific requirements of each project. This technology presents substantial time-saving opportunities for the on-site measuring operations and in-office model generation process while reducing errors and discrepancies between the virtual avatar and the existing building. Verification and confirmation of the reliability and exactitude of data surveyed is achieved with the assessment of reference points, using conventional measuring methods (laserscanning, optical measuring instruments, etc.)

As evidence of the effectiveness of this technology, more and more contractor veer from traditional surveying methods and engages services from specialized aerial-based photogrammetric survey companies for the measuring and monitoring works of heritage buildings comporting complex façade elements. Moreover, additional features are also providing interesting applications, for instance, the possibility of using thermal infrared cameras for specific underground investigations or waypoints navigation mode, where the device follows a distinct path previously defined by the controller.

The presence of drones on construction sites is about become common practice, thus confirming the enormous potential of this technology. It serves as further proof that the digitalization of the AEC industry is well under way and that the introduction of new working methods bears fruit.

 

For more information regarding building surveying with UAV devices, GIS, laserscanning and similar surveying method, take a look at this Guideline from the Runder Tisch GIS e.V.: Leitfaden Geodäsie und BIM (available in German)

 

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