Manual on Sea Level Measurement and Interpretation
This manual is concerned primarily with techniques for the measurement of what are called relative sea level changes which means changes relative to the level of the land upon which the measuring instrument (the tide gauge) is located. The subject of changes in the level of land itself is reviewed later in this document but is given more detailed presentation in other reports to which we refer. The manual also concerns itself primarily with the part of the frequency spectrum of sea level change from minutes through to centuries by means of in situ devices at the coast (tide gauges). Such changes are sometimes called still water level changes, being changes over a period long enough to average over wind waves. The devices employed to make these measurements are usually called tide gauges, although sea level recorders might be a more appropriate term. In this manual we have kept the older, conventional term.