Tower of the prime meridian of Italy

Viale del Parco Mellini, Monte Mario (Roma)
41°55’27.8”N 12°27’07.7”E (datum WGS84-ETRF2000)

In February 1870 the Pontifical government announced a geodetic surveying plan of the state of the church following the Berlin Conference of October 1864 for the measurement of the degree of the Central meridian of Europe. The triangulation had to make base on Monte Mario where was erected a “station-observatory astronomical-geodetic fundamental”. In fact, the meridian passing through the Dome of St. Peter’s Basilica did not meet the needs of a measure that was to be very precise and uniform in every country. The project was entrusted to P. Buckets, which in 1855 had measured the geodetic base along the Via Appia Antica. The original tower that materialized the point was shaped truncated-conical, square-based, high-C. 12.50 m, and was initiated in May 1870. The operations were interrupted due to the annexation of Rome to the Kingdom of Italy (September 1870), but the new Italian Government made the decision to use Monte Mario as the point of origin of the new National Geodetic Network (official decision Only in 1940, with the Datum ROMA 1940).
For the construction of the fort of Monte Mario, the Square tower was demolished in 1877 and the reference point of the longitudes was moved to the nearby Villa Mellini, now home of the INAF. Around 1882 the original point was reused, building a new circular-based truncated conical tower, 7.00 m high, at the circular witness buried at 4.00 m of depth.
The trigonometric point of Monte Mario, the first meridian of Italy, is located at 12 ° 27 ‘ 07.7 “E (Datum WGS84-ETRF89).
A plaque recalls the point of “origin of the Italian longitudes” (Figure 1), while a plaque, recently affixed, indicates the direction of the meridian (Figure 2).

Tullio Aebischer, SISFA

Bibliography
T. Aebischer: La torre del primo meridiano d’Italia in Semestrale di Studi e Ricerche di Geografia, 2, 2006, pp. 145-152; T. Aebischer, P. Battinelli: Un segno per il primo meridiano d’Italia a Roma in GEOmedia, 1, 2008, pp. 20-21; T. Aebischer: G.B. Beccaria e lo studio della forma e dimensione della Terra: il Gradus Taurinensis in Giornale di Astronomia, 40, 3, settembre 2014, pp. 18-23; T. Aebischer: Gnomonica geodetica: l’uso delle meridiane per studiare la Terra in M.L. Tuscano, a cura di: Atti del XIX Seminario Nazionale di Gnomonica, Cefalù (PA), 4-6 aprile 2014, pp. 14-17; T. Aebischer: 150° anniversario dell’istituzione della Commissione Geodetica Italiana (1865-1977) in Giornale di Astronomia, 42, 1, marzo 2016, pp. 25-33.