Tide gauge is a device for measuring sea level changes and detecting tsunamis. INCOIS has established a network of 36 tidal gauge stations along strategic locations of the Indian coastline to monitor progress of tsunami waves, as well as for validation of the model results. The data are transmitted in real time through different modes of communication like INSAT and GPRS simultaneously for processing and interpretation.

Tide gauges are very critical to monitor the tsunami progress and the coastal sea level changes. INCOIS installed three types of tide gauge sensors i.e. Radar (RAD), Pressure (PRS), and Shaft Encoders (ENC) at 21 locations (established in 2010-11) and one sensor (RAD) at 15 locations (established in 2015-16) to measure the water level heights.

Radar (RAD) gauge: The radar gauge emits microwave pulse and measures the distance between its reference point and the water surface with an averaging of the single high-rate measurements over a few seconds. The gauge is usually mounted on top of the tide gauge cabin with a U-profile steel girder. The maintenance of these sensors is very low when compared with other kind of sensors.

Pressure (PRS) gauge: This gauge measures the hydrostatic pressure of the water column and converts it into height based on knowledge of the water density and local acceleration due to gravity. The gauge is mounted in the sea water within a metal construction.

Shaft encoder (ENC) gauge: The shaft encoder records changes in the water level with a float in a stilling well that rises and falls with the tide. A pulley attached to the float causes the encoder shaft to rotate in response to vertical motion of the float. The position of the rotating disk is determined by single or dual optical or magnetic sensors to provide an electrical output.

All sensors are connected to a data logger, which provides data logging, storage and control functions for the sensors as well as the data transmission to the tsunami warning centre. Each tide gauge measures the sea level by sampling for every one minute and transmits it for every 5 minutes (Islands stations every 3 minutes). The data are transmitted in real time through different modes of communication like INSAT and GPRS simultaneously for processing and interpretation. INCOIS is equipped with an INSAT satellite communication hub, state-of-the-art computing hardware, real-time data processing and visualization facilities for real-time reception, display and archiving of tide gauge data.