UNDERGROUND SURVEYING: 16^TH CENTURY CELLAR VAULTS IN THE GALERÍA DE CONVALECIENTES, MONASTERY OF SAN LORENZO DEL ESCORIAL

Abstract. Underground surveying of cellars, caves, and architectural spaces, is quite different from surveying on the surface. Researchers must deal with various challenges derived of the lack of natural light, low temperature, and humidity, but also with inaccessibility. But the essential problem in underground surveying is that of orientating the underground surveys to the surface surveys. For this purpose our methodology integrates different geomatic techniques, as the use of a scanner laser in order to obtain a 3D model, as well as classic topography, and GPS to locate accurately the control points according to the official reference frame of the Spanish Geodetic Network. The developed methodology is described and applied to the case study of the cellars of the Gallery of Convalescents (Galería de Convalecientes) in the Royal Monastery of San Lorenzo de El Escorial. These cellars compose an outstanding series of interrelated singular complex spaces. Their study is particularly relevant because of the quality of the stonework, the geometry of the vaults and lunettes, and the stereotomy. The fact that these spaces were neither surveyed nor studied before, must be stressed. And our work will bring into light an important part of the 16th century Spanish architectural heritage. Finally, the INSPIRE Directive becomes an opportunity to integrate cultural heritage datasets into an interoperable framework, and to share and diffuse them as geographic information.