14
In the case of calculating hydrographs, the times are defined within a fixed grid
with 96 sampling points. The index k=1 is arbitrarily assigned to a point in time
1/8 Moon hour after transit in upper culmination plus MHWI; thus, this point in
time is approximately 7.8 min after the corresponding high water (Figure 1). The
other points in time 2 to 96 each follow in intervals of 1 /t Moon hours.
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93
1.4
1.2
0.8 E
0.6
0.4
0.2
Figure 1: Mean values (above, left ordinate scale [m above gauge zero GZ] and standard deviation
(below, right ordinate scale [m]) of complete data set (dotted line), of 3 SD filtered data set (thin
line) and of tidal synthesis (thick line), fixed grid with 96 sampling points.
Since the relevant angular velocities m- can be judiciously chosen from the
components of the tide-generating potential (Hartmann and Wenzel, 1995), this
is largely about determining the coefficients c k , . (1) and c k . (2), respectively.
This somewhat fickle calculation of coefficients is called tidal analysis; the sim
ple application of the equations (1) and (2), respectively, is called tidal synthe
sis.
Given the consequent application of the identifier Moon transit, the tidal analy
sis is easy to accomplish. This becomes particularly evident by the arguments
of the trigonometric functions in (1) and (2) co, ■ i, respectively. The angular
velocity, recorded as °/Moon day, acquires values between 0 and 100 °/Moon