Recovering the Vestiges of the Old Meridian Arc of Paris in the Valencian Community of Spain

This paper describes research carried out both to obtain the location and identify possible vestiges of the old geodetic benchmarks used by the expedition formed by French geodesists Arago and Biot and Spanish geodesists Chaix and Rodriguez, to carry out the prolongation of the meridian arc of the Paris Observatory in the Valencian Community in the early 19th century in order to define the meter as the base unit of length of the International System of Units. Geodetic, historical, and field work methodologies were integrated in the study to obtain scientifically sound results, which include the determination of coordinates of the original geodetic benchmarks and the successful identification of several remains. An outstanding typical error of 0.4 '' for the old angular measurements can also be deduced from the analysis. Conversely, several old altitudes were found to have errors or considerably lower accuracies than those expected, around 1 m.