2008-05-23

The 12 German reference stations were originally generated with no
consideration for whether the time serieses were long enough to separate all
of the constituents.  The plan here was to regenerate the German reference
stations from the original time serieses using the 1-year constituent set and
to suppress constituents whose amplitudes were below the noise.

While regenerating the stations with the 1-year constituent set appeared to
improve the matching of heights to authoritative predictions, it had a
negative effect on the matching of times.  Suppressing low-amplitude
constituents did not help.  Reducing each station to 40 constituents made it
worse.

To eliminate breakage of the software as a contributing factor, the original
results were successfully reproduced with Octave 3.0.1 and harmgen 3.1
(--force congen_9yrs.txt).  The harmonics file was then left unchanged
(retaining the data as generated in 2004).


Compare with http://www.bsh.de/en/Marine_data/Forecasts/Tides/index.jsp
"chart datum"
Compared 2008-05-23 local time (1 day)
Time delta in minutes, height delta in meters (rounded to 0.1 m)


OLD = 2004 data
NEW = 1 year constituent set, amplitude cutoff 0.01 m

                           OLD                            NEW
                 time delta   height delta      time delta   height delta
Büsum                10           0.3               15            0.2
Bremerhaven           7           0.3                6            0.2
Bremen               13           0.3               15            0.2
Brunsbüttel          10           0.3               11            0.4
Borkum                9           0.3                9            0.2
Cuxhaven              6           0.3               16            0.4


OLD = 2004 data
NEW = 1 year constituent set, no cutoff

                           OLD                            NEW
                 time delta   height delta      time delta   height delta
Büsum                10           0.3               17            0.2
Bremerhaven           7           0.3                6            0.2
Bremen               13           0.3               12            0.2
Brunsbüttel          10           0.3               13            0.3
Borkum                9           0.3               13            0.2
Cuxhaven              6           0.3               15            0.2


OLD = 2004 data
NEW = 1 year constituent set, limit 40 constituents

                           OLD                            NEW
                 time delta   height delta      time delta   height delta
Büsum                10           0.3               17            0.2
Bremerhaven           7           0.3                9            0.3
Bremen               13           0.3               22            0.4
Brunsbüttel          10           0.3               16            0.3
Borkum                9           0.3
Cuxhaven              6           0.3