This paper describes the photogrammetric 3D modelling of complex buildings using low-cost automatic image matching (AIM), consumer-grade digital cameras and low-altitude imagery. To verify the potential of this method, it was applied to the documentation of a specific case: the towers and roofs of the Cathedral of Santiago de Compostela in Spain, a UNESCO World Heritage Site. The design and development of a mechanism for coping with the elevation, based on telescopic masts, was essential. Models, orthophotos and plans have been obtained to determine and rigorously measure the geometry involved. Thereby it was possible to accurately record the materials and decorative elements based on the restitution of the granite stones. Furthermore, close range photogrammetry made the analysis and quantification of the inclination of the south tower possible.

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Infrared thermography (IRT) techniques for building inspection are currently becoming increasingly popular as non-destructive methods that provide valuable information about surface temperature (ST) and ST contrast (delta-T). With the advent of unmanned aerial vehicle (UAV)-mounted thermal cameras, IRT technology is now endowed with improved flexibility from an aerial perspective for the study of building envelopes. A case study cellar in Northwest (NW) Spain is used to assess the capability and reliability of low-altitude passive IRT in evaluating a typical semi-buried building. The study comparatively assesses the use of a pole-mounted FLIR B335 camera and a drone-mounted FLIR Vue Pro R camera for this purpose. Both tested IRT systems demonstrate good effectiveness in detecting thermal anomalies (e.g., thermal bridges, air leakages, constructive singularities, and moisture in the walls of the cellar) but pose some difficulties in performing accurate ST measurements under real operating conditions. Working with UAVs gives great flexibility for the inspection, but the angle of view strongly influences the radiometric data captured and must be taken into account to avoid disturbances due to specular reflections.

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Photogrammetry is a commonly used technique in three-dimensional image-based modelling for cultural heritage documentation. Three-dimensional image-based techniques that combine close-range photogrammetry and automatic image matching are presently attracting a great deal of interest. This paper evaluates the feasibility of the application of photogrammetric three-dimensional modelling of an archaeological site with close-range automatic image-matching software and a consumer-grade digital camera. In order to correctly model upward-facing surfaces using this technique, the photographs were taken from the air with the camera in low-oblique position. A mast pole was used as camera platform to obtain low-altitude imagery. To verify the usefulness of this method it was applied to the hill fort 'Castro de Formigueiros', located in Lugo, Spain. In this case, low-cost automatic image-correlation photogrammetry has proved to be a powerful, cost-effective and versatile technique for the documentation, analysis and cultural dissemination of archaeological mapping. The mast used is inexpensive, easily transported and handled on site, and allows oblique photographs of the ground and wall-tops to be obtained at distances similar to photographs of vertical wall faces taken from the ground. As a result, the resolution and accuracy of the point clouds of all the surfaces of the final model are similar. Given the geometric peculiarities of hill forts (the occupied surface area, height, volume and distribution of the objects) and the relief (they are generally located in areas difficult to access and often on high ground), the mast is particularly suitable for photographing low-altitude imagery at archaeological sites, as the final accuracy of the three-dimensional model demonstrates. The tools that have been applied to the final digital model of the hill fort show the information analysis potential that can be obtained for archaeological work.