GeoWerkstatt July: Chronometric Levelling to Establish a Global Height System

How high is Mount Everest actually? Nepal and China did not agree on this question for a long time - because they each used their own reference system for measuring altitude. An agreement was reached at the end of 2020. The reason: the two countries now used an international height reference system as the basis for their measurements. The reference value is no longer a specific sea level ("above sea level"), but a so-called global equipotential surface. This refers to the Earth's gravitational field: all points on the equipotential surface have the same gravitational potential. In order to measure the height of locations on the earth, one simply determines the respective deviation from this gravitational potential. The current Geowerkstatt project shows that optical atomic clocks are particularly suitable for these measurements.