Gisemundus and the orientation of the romanesque churches in the spanish pyrenees (11th-13th centuries)

Abstract

This study examines an ensemble of thirty-two Romanesque churches in the region of Boí Valley and Aran Valley in the Spanish Pyrenees, built between the 11th and 13th centuries. The data obtained allowed for a geometric study of the orientation of these churches based on four Romanesque liturgies: Gemma animae (c.1120), by Honorius of Autun; Rationale divinorum officiorum (c.1150), by Jean Beleth; Mitralis de Officio (1190), by Sicard, Bishop of Cremona; and Prochiron, vulgo rationale divinorum officiorum (1291), by Guillaume Durand. A group of these churches have been equinoctially oriented. The mountainous topography does not allow a setting-out by observing the solar ortho, because the angular altitude of the skyline (AAS) is >0º. Therefore, we conclude that, due to their precision azimuth (Az) (91.41º, ± 1.91º), they have been traced using instrumental systems inherited from Vitruvius, Hyginus Gromaticus, Gisemundus, or Gerbertus Aureliacensis. It is concluded that the method of land surveying sources of Gisemundus (c.800), is the one that geometrically allows the sacral orientation from East to West to be plotted with less error