Kronstadt Tide Gauge

The Kronstadt tide gauge, located on the Blue Bridge across the Obvodny Canal, is metric and graduated in centimeters. In 1840, at the suggestion of hydrographer Mikhail Reinecke, a mark corresponding to the average water level of the Gulf of Finland was made on the stone abutment of the bridge. In 1913, the head of the port's instrument chamber, H. F. Tonberg, installed a new plate with a horizontal line, which serves as the starting point for the leveling network of Russia. To control the immutability of the zero position of the tide gauge, it is linked to the upper stroke of the letter "P" in the word "Benefit" on the monument to Pyotr Pakhtusov, and a meteorologist manually records readings from a paper recorder four times a day.