IBGE will finish, next April 19^th, the installation of the fifth station of the Permanent Tide Gauge Network for Geodetics (RMPG) at the Port of Mucuripe, located  in Fortaleza (CE), in order to measure sea level at that point of the coast.  By sea level measurement it is possible to determine the maximum, medium and minimum altitude of tides, so as to enable the construction of ports or jetties. These stations are also relevant to altimetry (since the average sea level is the origin of altitude). The digital equipment for the station was donated by the Global Sea Level Observing System of the Intergovernmental Oceanographic Commission of UNESCO (GLOSS/IOC), through a partnership with the Brazilian Navy, by which IBGE has been invited to integrate the GLOSS-Brazil group.

The installation of the equipment in Fortaleza started in September last year, when IBGE built the supporting structure to the installation of digital tide gauges and installed a conventional tide gauge (a mechanic one with results in paper) in order to make it possible to obtain digital data from these first registers. Between April 10^th and 19^th two tide gauges will be installed in Fortaleza – a digital radar sensor which works on energy taken from solar panels or electricity, and one of the encoder type, which is a mechanic appliance for digital data registration. The appliances measure sea level every five minutes and send the information every hour to the GOES satellite (international geostationary satellite) and, every day, transmits it to the Tide Gauge Network through a telephone line.

The implementation of the Fortaleza station has been done according to a schedule planned in 2000, and which predicted that six other tide gauge stations would be installed along the Brazilian coast. The stations installed so far are those of Imbituba, in Santa Catarina (2001), Macaé, in Rio de Janeiro (2001; it is worth mentioning that, in 1994, IBGE took charge of a conventional tide gauge which belonged to Petrobrás), Salvador, in Bahia (2004) and Santana, in Amapá (2005). The implementation of another Tide Gauge Network station is expected to occur in Belém, in Pará. The stations which form the network are distributed among strategic points along the Brazilian coast, once the sea level can vary significantly from place to place.

The study of tides is a permanent activity, since sea level undergoes frequent changes. Some of the reasons accounting for these changes are the rotational movement of the Earth (which lasts approximately 14 months); the nodal cycle of the moon (which lasts approximately 19 years); sunspot cycles (duration of about 13 years); meteorological phenomena (especially winds and atmospheric pressure);   the movement of ocean currents, among other oceanographic phenomena.