A common method for determining mean sea levels is to use tide gauges. This device measures the periodic tidal changes in sea level over a long period of time at the installation site. Tide gauge, which also includes a graduated ruler, is one of the most convenient and reliable methods of measuring the water level at any point and time. Depending on the type, this device is installed on the shore outside and near the sea water, in the water in the rocky wall of the beach, or on the sea floor. At the entrance of ports or river canals near the shore, where the Tide Gage and Tide Bridge devices are located, it is possible to read the water level from the Tide Gage with a difference of 10 +/- cm from the hydrograph boat, dredging ship or other ships by the camera.
Sea water measurements are either continuously and analogously plotted on a millimeter-scale paper or stored digitally at regular intervals. The height of the instantaneous surface is measured relative to the device itself (zero device). If the height difference of the device compared to a benchmark located on the beach is known, sea level changes can be obtained compared to the benchmark on the beach.
In large and crowded ports, it is necessary to use automatic tide gauges or mariographs to analyze the tidal height to accurately predict the height of the water. Also, water sampling and recording for a long time are required for application in tidal calculations. The reliability and accuracy of an automatic tide gauge is very important and is achieved through the following:
- Careful study of Tide Gage location because the quality of the recording is affected by the turbulence of the water surface and the irregularity of the location in the propagation of water height.
- A platform with a frame on which Tide Gage is located and is precisely adjusted based on the geographical map of the area.
- Automatic gauge stability tested optimally.
- Regular and periodic maintenance and repair, especially floating tide gauge tube to remove any obstacles in sending data to the desired centers.