Abstract: A system for monitoring a mechanically coupled structure with a first sensor configured to determine at predetermined times its orientation relative to Earth's rotation axis as a first measurement. The first sensor is connectable with a first part of the mechanically coupled structure with at least one second sensor which has a known first orientation to the first sensor at startup of the system and which is configured to determine a rotation rate or an acceleration as a second measurement. The at least one second sensor is connectable with a second part of the mechanically coupled structure with a central unit and with a communication network over which the central unit is connected with the first sensor and the second sensor wherein the first sensor is configured to transmit the first measurement to the central unit.