7 
Introduction 
1 Introduction 
For the German coastal waters, comprehensive tide gauge time series of good 
quality are available; since the mid-1990s, these are available also at minute 
intervals. In the course of extensive research projects on global climatic fluctua 
tions, the development of the relative sea level at some German gauging sta 
tions has likewise been researched In greater detail (Wahl et al., 2011). 
The motivation for this paper Is, for one, the public documentation of the Ger 
man Federal Maritime and Hydrographic Agency tidal analysis procedure and, 
far more importantly, the fact that soon (about end of 2014) minute interval dig 
ital tide gauge data spanning 19 years will have been collected and been 
made available. More diversified operational harvesting of the data flow is de 
facto being demanded, yet this will not be possible without considered atten 
tion to the tidal proportion. Recently, a report was published by the technical- 
scientific association for water-borne transport, navigation, ports and water 
ways PIANC, which highlights the future significance of operational data serv 
ices for the accessibility to sea ports (PIANC, 2012). Tidal analyses and 
predictions have a long-standing tradition (Cartwright, 1999). So far, three dif 
ferent procedures have emerged to achieve practical significance, mostly as 
regards the production of tide tables: 
• the non-harmonic procedure, 
• the harmonic procedure and 
• the harmonic representation of inequalities. 
The non-harmonic procedure for calculating tides (of semidiurnal form) is a pro 
cedure rendering the high and low water times of a given location by adding to 
the Moon’s meridian transit times the mean high and low water intervals as well 
as the inequalities in high and low water times. The high and low water levels, 
i. e. marks, are rendered by adding the inequalities of high and low water 
heights to the mean high and low water heights. The four inequalities regarding 
time and level themselves are derived from the combination of one semi 
monthly, parallactic, declination and daily inequality each as well as, as the 
case may be, also from other improvements. 
The harmonic analysis of tides (e. g. Pansch, 1988, with further sources) 
derives from an similar decomposition of the tidal forces into harmonic parts 
(Hartmann and Wenzel, 1995). The angles of the individual tides, also called 
constituent tides, increase steadily with the local time. The various periods of 
the individual tides derive from the study of the movements of the Moon and the 
Sun; these are the same for any location on Earth. Conversely, the amplitudes 
and phases of the constituent tides are generally different from location to loca 
tion and mark the different cycle of tides at individual locations.