Manual on sea level measurement and ... - unesdoc - Unesco

Sea Level Measurement and InterpretationChilean Sea Level NetworkJuan Fierro, Chilean Navy Hydrographic and Oceanographic Service (SHOA)E-mail: jfiero@shoa.clIn 1941, the Chilean Navy Hydrographic andOceanographic Service (SHOA) initiated the establishmentof the national tide gauge network with theobjective of starting a systematic and permanentrecording of the sea surface level along the coast.Figure 2. Sea level station configuration.obtained has been of great value to the national andinternational scientific communities.Figure 1. Chilean sea level network.At the end of 1950, the network consisted of five tidegauge stations, and the experience gained during itsdeployment and operation was extremely important fora successful extension of the network.The great length of the Chilean coast and the accessibilityproblems in some areas have been the mainobstacles to extending the network in the short term.However, at the end of 1998, the sea level networkcomprised 19 permanent tide gauge stations, locatedon the mainland as well as in some islands and inAntarctica. Considered as a system, the operationof this network has allowed SHOA to provide usefulinformation to mariners sailing in Chilean waters andto contribute to engineering projects associated withcoastal-zone management. Moreover, the informationThe upgrading initiated in March 1999 considered thedeployment of 17 HANDAR model 555C data-acquisitionplatforms, as shown in Figure 1. The new platforms,with satellite data-transmission capability, replaced theold recording tide gauges, whose operation was basedon nitrogen gas pressure. The present tide gauge station’scharacteristics are shown in Figure 2.For the comparison of old and new gauges, six monthsof overlapping (concurrent) operation were considered.During this time, both systems operated in parallel andintercomparisons were performed. Sea level data andancillary data collected by the sea level network weretransmitted via the GOES satellite system. Incoming sealevel data were validated using a quality-control packageprovided by the University of Hawaii. Plots of newcomputations of yearly residuals showed fewer errorsin comparison with previous findings.The standard configuration of every sea level stationincluded a water-column pressure sensor, an atmo-72IOC <strong>Manual</strong>s and Guides No 14 vol IV