In this project we investigated in cooperation with Linsinger civil engineering methods with which one can carry out inventory and recognition as well as documentation of changes to buildings - preferably in the area of cultural heritage - as precisely and efficiently as possible. Both terrestrial scanners and drones were used to capture the buildings as a whole. The methods used include laser scanners, photogrammetry, thermography and photometry in order to detect even the smallest changes.
Restorations and building projects in the building are playing an increasingly important role in the field of building management. Building inventory documentation therefore forms the basis for all types of planning. In the meantime, data acquisition using 3D laser scanners and subsequent evaluation has established itself in the field of internal service. This provides an effective planning tool for the architect, restorer and craftsman. However, many historic buildings can only be partially viewed from the ground or from a lifting platform: The Cologne Cathedral - a parade example from the repertoire of Linsinger ZT – cannot be viewed completely from the ground. In such cases, unmanned aerial vehicles (UAVs, usually referred to as "drones") are increasingly used. They are equipped with high-resolution cameras that can produce hundreds of photographs of the building from many angles within a short time.
From these "photo clouds" a three-dimensional model of the building can be calculated by means of photogrammetric methods on highly parallel computer clusters. These models can be viewed in real-time from all sides and serve both to document the actual state as well as to create conventional representation, such as a line drawing in orthoprojection, which represents an arbitrarily large part of the facade undisturbed.
By using the methods described above, the condition of buildings can be described very well, but some aspects of aging are difficult to detect: efflorescence and mossing is difficult to identify visually or from photogrammetric reconstructions. For this reason, we are combining additional methods with the existing ones in this project: Photometric methods allow the reconstruction of minimal differences in height, even brush strokes and scratches are clearly visible. As a result, the course and spread of minor changes in the surface can be tracked and documented. Far Infrared Vision - FIR, also referred to as thermal photography - allows to detect and display the slightest differences in the temperature profile, for example, due to spalling or vegetation. A combination of visible light and FIR allows us to fuse the detailed reconstruction of buildings with the measurement of finest temperature differences (<0.04K).
Impact and effects
The combination of multispectral data with the high resolution of photometric reconstruction allows the long-term observation of the subtlest changes to the building. As a result, potential damage points can be detected in a timely manner in order to avoid greater damage or even danger to persons.