Gisemundus and the Orientation of the Romanesque Churches in the Spanish Pyrenees (11th – 13th Centuries)

A precise azimuth of 91.41° (±1.91°) in the orientation of equinoctially aligned Romanesque churches in the Spanish Pyrenees suggests the use of advanced land surveying techniques inherited from medieval scholars like Gisemundus, rather than direct solar observation. The study analyzed 32 churches built between the 11th and 13th centuries, comparing their orientations to liturgical texts from the period. Given the mountainous terrain's obstruction of solar sightlines, the researchers concluded that these churches likely used geometric methods—such as those described by Gisemundus (c.800)—to achieve accurate east-west alignment with minimal error.

Ginovart, J. L. i, Ugalde-Blázquez, I., & Lluis-Teruel, C. (2021). GISEMUNDUS AND THE ORIENTATION OF THE ROMANESQUE CHURCHES IN THE SPANISH PYRENEES (11TH – 13TH CENTURIES). Zenodo. https://doi.org/10.5281/ZENODO.4574636