This paper presents a new automated method for the detection and determination of building heights using their cast shadows. The approach consists in applying image processing using PCA and segmentation for the detection and recognition of buildings and their shadows. The height of the buildings is deduced by knowing the length of their shadow projected on the ground, the position (azimuth and zenith) of the sun and the sensor at the time of acquisition. These shadow analyses were carried out on a free satellite image from Google Earth. The results of the height calculations are used for the three-dimensional modelling of the buildings.The 3D models produced can be used for strategic decisions in the professional field and for urban monitoring and surveillance, as well as for various research studies on the relationship between building heights and natural and man-made phenomena: energy consumption and land subsidence. Our method, which requires a good precision of the geometric characteristics of the proposed remotely sensed data, has outperformed the majority of existing research as an automated approach to exploiting the shadows of several buildings in a single satellite image and their 3D reconstruction.

Boujad is a Moroccan city located in the region of Beni Mellal - Khenifra, and is considered until now as a spiritual center welcoming travelers from the Kingdom in search of religious precepts. Investigations carried out in the ancient medina of this city reveal the presence of underground cavities of natural and anthropic origin, which repeatedly cause collapses and considerable human and material damage. In order to characterize the subterranean network of this city, a geophysical study was carried out by means of electrical prospecting of the subsoil, complemented by a seismic refraction investigation, in order to investigate the geological and geophysical characteristics of the underground cavities, and then to produce a detailed mapping of the anomalies detected within the ancient medina of Boujad. The geophysical investigations thus revealed a heterogeneous subsoil dominated by limestone formations and sheltering several underground anomalies, and allowed, by superimposing the maps of anomalies drawn up at the end of each technical investigation, then correlating and verifying the results collected in relation to the data from the surveys and preliminary investigations, to draw up a synthetic map of the main areas concerned by the presence of cavities which are quite varied and spread over the entire extent of the ancient medina of Boujad.