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Earthen Domes and Habitats
Fig. 16: Er Raheb (a), orthophotos relative to the four elevations of the form model of the entire dwelling unit.
Topographical survey Er Raheb (b) ER(b) is an open dwelling unit with two pseudo-conic domes (Sultan dome). It was possible to survey the interior of ER(b) to study the qualitative and quantitative aspects of the isolated-type construction system composed of two cells connected by an archway. The topographic traverse had four principal vertices (100, 200, 300, 500) and one secondary vertex (400) for reading the signals placed inside the dwelling unit. 18 targets were used: these were essential during the alignment phase of the points clouds generated by the scanning systems. 8 scans were carried out from different positions: 5 outside, 2 inside and 1 uniting inside and outside. For obvious reasons a higher resolution was used for the outside scans than for those carried out inside; this was quantified on a grid made up of points placed at 0.5 cm intervals when the object was 10 m away and placed at up to 3 cm intervals at a distance of 50 m.
duced during scanning (Fig. 18). The retro-projection of an oriented photogram takes place in such a way that each ray of the star of directions meets the form model of the object: the objective in this instance is not the reconstruction of the form of the building, which should already be known, but the calculation of the ‘photographic coloration’ to attribute to each tiny portion of the surface of the object. Orthogonal viewpoints relative to the four elevations of the form model of the entire dwelling unit were set up and the corresponding orthophotos were calculated (Fig. 16).
The graphic output The three-dimensional points model obtained after aligning all the 3D scans constitutes a real database: it is an extremely dense and sufficiently accurate ‘information depot’ from which all the required graphic output can be successively derived. The wealth of information contained in these models is valorised by the possibility of visualizing and exploring them interactively with the appropriate software. The model acquires the role of significant referent of the object, and it is possible to observe the model as if it were the object itself: the mod-