A system consisting of a device such as a tide gauge for measuring the height of sea level, a data collection platform (DCP) for acquiring, digitizing, and archiving the sea level information digitally, and often a transmission system for delivering the data from the field station to a central data collection centre. The specific requirements of data sampling and data transmission are dependent on the application. The GLOSS programme maintains a core network of sea level stations. For local tsunami monitoring, one-second sampled data streams available in real time are required. For distant tsunamis, warning centres may be able to provide adequate warnings using data acquired in near-real time (one-minute sampled data transmitted every 15 minutes or better). Sea level stations are also used for monitoring long-term sea level change and climate change studies, where an important requirement is for the very accurate location of the station as acquired through surveying techniques.