Paul Adrien Bourdaloue, born in Bourges in 1798 and deceased in Bourges in 1868, was a French engineer and topographer who proposed the first orthometric levelling system in France. He served as resident engineer for the Gard railway. From 1847 onward, he carried out the levelling of the area that would become the Suez Canal in Egypt.
There, he observed that the difference in sea level between the Mediterranean and the Red Sea was negligible—contrary to what Bonaparte’s engineers had believed.
In 1850, he presented his findings to the Académie des Sciences and was made a Chevalier of the Légion d’Honneur.
He was also named a Chevalier of the Order of Saints Maurice and Lazarus by the Duke of Savoy, Victor Emmanuel, King of Piedmont-Sardinia.
From 1857 to 1863, he was entrusted with conducting the general levelling of France. He created a network of baseline lines passing through all departmental capitals, materialized by a grid of 15,000 embedded cast-iron benchmarks—France’s first national levelling lines.
The reference datum for this system, the sea-level height at Marseille, was set by ministerial decree on 13 January 1860.
This datum became known as the “Bourdaloue zero.”
Bourdaloue also served as deputy mayor of Bourges. In 1865, he entrusted architect Tissandier with the design of the Séraucourt water tower in Bourges, which still stands today and now serves as a cultural venue.