Bitung, Sulawesi Utara

Mixed, mainly semidiurnal

Period: 01 Jan 2026 — 01 Agu 2026212 days
Datum: Nol sensor stasiun (bukan MSL)
gaps: 27707 jam
Source: IOC Sea Level Station Monitoring Facility (UNESCO/IOC & VLIZ)

Source, licence and datum notes

IOC menyajikan data mentah terhadap nol sensor masing-masing stasiun. Tinggi di sini tidak merujuk MSL, LAT, maupun chart datum.

Licence: Akses terbuka dengan kewajiban sitasi (VLIZ/IOC, DOI 10.14284/482)

Flanders Marine Institute (VLIZ); Intergovernmental Oceanographic Commission (IOC) (2026): Sea level station monitoring facility. https://www.ioc-sealevelmonitoring.org — DOI 10.14284/482

Not for navigationThe official Indonesian tide tables are published by Pushidrosal.

Constituents

Harmonic constituents

Amplitude, phase and frequency per constituent. The ones the record cannot honestly resolve are marked, not reported.

Condition number κ: 1.65good
Residual RMS: 0.0758 m
Mean level Z₀: 7.8795 m
Record length: 212.0 days

Harmonic constants per constituent
Constituent	Amplitude H (m)	Phase g (°)	Lag (h)	Speed (°/h)	Period (h)	Nodal factor f	Nodal correction u (°)
M2255.555	0.3414±0.0017	277.0±0.3	9.56	28.984104	12.421	0.9663	0.85
S2273.555	0.2254±0.0017	314.5±0.4	10.48	30.000000	12.000	1.0000	0.00
K1165.555	0.2077±0.0015	310.1±0.4	20.62	15.041069	23.934	1.1057	3.09
O1145.555	0.1201±0.0014	291.2±0.7	20.89	13.943036	25.819	1.1710	-3.50
K2275.555	0.0677±0.0013	307.4±1.1	10.22	30.082137	11.967	1.2919	6.60
P1163.555	0.0630±0.0017	309.5±1.5	20.69	14.958931	24.066	1.0000	0.00
N2245.655	0.0508±0.0017	269.5±1.9	9.47	28.439730	12.658	0.9663	0.85
Q1135.655	0.0251±0.0014	287.6±3.2	21.47	13.398661	26.868	1.1710	-3.50
M4455.555	0.0072±0.0017	170.0±13.8	2.93	57.968208	6.210	0.9338	1.70
MS4473.555	0.0060±0.0017	258.4±16.0	4.38	58.984104	6.103	0.9663	0.85

H is half the height of that constituent’s wave; g is how late it arrives behind the Moon or Sun, and the column beside it says the same thing in hours — g divided by the constituent’s speed. f and u are the 18.6-year corrections, applied and still shown.

The ± figure is one standard error, taken from the diagonal of the solve’s covariance matrix. It assumes the record’s noise is independent from hour to hour, and tidal residuals are not: weather lasts for days, so neighbouring hours are wrong in the same direction. The true uncertainty is larger than what is printed here — by how much, this site does not compute.

The geometry

How alike these constituents look to the record

The condition number says this solve was hard; the Rayleigh criterion says which pairs are impossible. Between them sits the thing neither reports: how hard, and because of whom. Each number below is the cosine of the smallest principal angle between two constituents in this record — 0 means cleanly separable, 1 means indistinguishable.

The most nearly parallel pair in this record: K1 / P1 (0.262).

Correlation between constituents in this record
	M2	S2	N2	K2	K1	O1	P1	Q1	M4	MS4
M2	—
S2	0.03	—
N2	0.04	0.01	—
K2	0.03	0.26	0.01	—
K1	0.00	0.00	0.00	0.00	—
O1	0.00	0.00	0.00	0.00	0.03	—
P1	0.00	0.00	0.00	0.00	0.26	0.04	—
Q1	0.01	0.00	0.00	0.00	0.01	0.04	0.01	—
M4	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	—
MS4	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.03	—

all but indistinguishable≥ 0.9
strong≥ 0.6
moderate≥ 0.3
slight≥ 0.1
negligible≥ 0.0

Computed from the design matrix that was actually solved, so it sees the record’s real sample times rather than only its span, which is all the Rayleigh criterion sees. What matters is not how many hours are missing but where: one long outage cuts the effective span and lets a hard pair collapse back together, while the same number of hours missing at scattered times costs almost nothing. Björck & Golub 1973.

The 18.61-year cycle

What f is actually correcting for

The lunar node regresses once in 18.61 years, and modulates the amplitude of every lunar constituent as it goes. In the table above f is just a column, and “f = 1.037” reads as a rounding correction. It is not: across that cycle K2’s f runs from 0.748 to 1.317 — the same wave stands at three quarters of its nominal height at one point and four thirds at another.

M2f 0.966 ±4%
K1f 1.106 ±12%
O1f 1.171 ±19%
K2f 1.292 ±28%
N2f 0.966 ±4%
Q1f 1.171 ±19%
M4f 0.934 ±7%
MS4f 0.966 ±4%

range of f over one cycle

where this record sits

f = 1, if the node were ignored

Solar constituents do not follow the lunar node at all — f = 1 and u = 0, for all time: S2, P1.

The reported amplitude H has f divided out, so it does not depend on the cycle; the wave actually in the water is H·f. That is why f and u are recomputed at prediction time rather than carried forward from the fit window — a harmonic constant is a constant with respect to an epoch, and copying one without its epoch is the kind of error that never shows in the output. Series from Schureman 1958, SP 98, table 14.

Tidal character

Formzahl number and tide type

Two high waters and two low waters a day, but of differing height and spacing.

Formzahl F

0.578

Mixed, mainly semidiurnal

F = (K1 + O1) / (M2 + S2) = (0.208 + 0.120) / (0.341 + 0.225)

Published values, for comparison

Segara Anakan0.557
Teluk Balikpapan0.370
Teluk Banten—
Tanjung Priok—

The published values above are for comparison only. Not one of them is an input to any number computed on this page.

Shallow water

The rise and the fall are not the same length

In shallow water, friction on the sea bed moves some of M2’s energy into multiples of its frequency, M4 above all. One half of the wave steepens and the other flattens: the water rises faster than it falls, or the reverse.

The flood is faster

The water rises in less time than it falls. Flood currents run stronger and shorter, ebb currents weaker and longer.

moderate

The tide as it runs

Time to rise

Time to fall

6.64 h6.47 h

M4/M2 ratio

0.0211

Relative phase 2g(M2) − g(M4)

24°

From M2 and M4 alone — Time to rise

6.14h

From M2 and M4 alone — Time to fall

6.28h

Interactive

Constituent explorer

Start with M2 alone — a clean twice-daily wave. Add S2 and the spring-neap rhythm emerges from the beat between two cosines.

Semidiurnal

Diurnal

Shallow water

Computing…