The Eiffel Tower was used as a giant reference point to create the first highly accurate topographical maps of France.

When the Eiffel Tower was completed in 1889, it stood at 300 meters, making it the tallest man-made structure in the world at the time. This immense height provided a unique advantage for geodesy, the science of measuring Earth's geometric shape and orientation. Gustave Eiffel himself encouraged scientific use of the tower to ensure its survival beyond its original 20-year permit.General Gustave-Auguste Ferrié and other French scientists utilized the tower as a primary station for the 'Triangulation of France' project. Triangulation involves measuring the angles between two known points to calculate the location of a third point. Because the tower was visible from great distances, it served as a fixed 'zero point' for surveyors to align their instruments and verify calculations across the Parisian basin.This work was critical for the Service Géographique de l'Armée, which sought to replace outdated 18th-century maps with modern topographical data. The accuracy provided by the tower helped establish the 'Nouvelle Triangulation de la France' (NTF), which remained the national standard for decades. These precise measurements allowed engineers to plan the expansion of the French railway system with unprecedented geographical certainty.Beyond mapping, the tower's height enabled groundbreaking experiments in meteorology, aerodynamics, and radio telegraphy. In 1910, the tower was even used to synchronize time signals via radio, allowing ships at sea to determine their longitude more accurately. Today, the Eiffel Tower continues to host over 100 antennas, maintaining its legacy as a vital piece of scientific and communication infrastructure.