Manual · Harmonic Tide

01 · Quick start

Four steps to your station.

The most reliable way is a fixed station number. You find all settings in the Garmin Connect app on your phone, under watch faces at Harmonic Tide.

Search for a stationOpen the station list and search for your harbour, your town or your coordinates.
Pick the matching stationTake the station whose setting is most like yours: same coast, same bay or same estuary. That is not always the nearest one.
Enter the numberSet “Tide station” to “Station number” and enter the number under “Tide: station number”.
Save and checkThe watch loads the station right away. When you open the settings again later, “Active tide station” shows which station the watch is using.

Settings · Harmonic Tide

Active tide station: No. 1368 · Cuxhaven Steubenhöft (DEU)
Tide station: Station number
Tide: station number: 1368
Tide: latitude
Tide: longitude

Example Cuxhaven: the coordinate fields stay empty while you use a station number.

02 · The three modes

Automatic, number or coordinates?

The “Tide station” setting decides how the watch picks its station. All three use the same database and calculate equally well. They only differ in which station is chosen in the end.

Automatic

For being on the move, such as travelling or sailing along the coast.

Takes the station nearest to the watch’s last known position. That position comes from your last activity with GPS or from the weather data.
Only switches when a new station is at most 50 km away and at least 2 km closer. Inland, the last station stays.
The nearest station is not always the best match, for example on the other side of a peninsula.

Up to about 5 minutes

Recommended

Station number

For your home harbour or a fixed place you know well.

You decide which station applies. The watch needs no location for it.
The station stays fixed, even when you travel.
The number comes from our station list. Numbers from NOAA, the BSH or other services do not work here.

Loaded instantly

Nearest to coordinates

For a particular place where you are not right now, such as your next destination.

Enter latitude and longitude in decimal degrees, with a point or a comma. Cuxhaven, for example, is 53.87 and 8.72.
For places south of the equator or west of Greenwich, put a minus sign in front of the number.
The watch picks the station nearest to that point. It stays until you change the coordinates.

Up to about 5 minutes

Tip: the station list can also sort by distance to coordinates. That way you see in advance which station the watch will choose, and you can enter its number as a fixed station right away.

03 · Optional

Local correction.

If your harbour lies further up an estuary or behind islands, high and low water arrive a little earlier or later there than at the station. With one pair from your local tide table, the watch evens this out.

Pick a high water from your tide table and enter its date and time.
Enter the low water that directly follows in the same way.
The watch shifts the station’s times to match. “Active tide station” then says “local correction”.

04 · Common questions

Answered briefly.

How long until my station is ready?

With a station number, instantly. In automatic and coordinate mode the watch searches in the background, which usually takes just a few minutes, about 5 at most. Until then the watch shows “Finding tide station”.

The watch says “Waiting for location”. What now?

Automatic mode needs a position. Briefly start an activity with GPS outdoors, or wait until the watch receives weather data from your phone. Or simply enter a station number.

“Active tide station” says “No station”.

The number does not exist or the coordinates cannot be read. Valid numbers run from 1 to 1998. Please enter coordinates in decimal degrees, so 53.87 rather than 53° 52′.

Which station suits my place best?

The one whose setting is most like your place. A station on the open coast is a poor match for a harbour deep inside a bay or estuary. If in doubt, compare two stations with your local tide table and take the one with the closer times.

How accurate are the times?

Compared with official NOAA predictions, the times of high and low water are usually only a few minutes off. The watch knows nothing about wind, air pressure or river water. Where the tide runs very flat, a turning point can also shift noticeably.

Why do the heights not match my tide table?

The watch measures heights from the station’s mean water level. Tide tables usually refer to chart datum. The difference between high and low water still matches, only the reference point is different.

Does the watch need a phone or the internet?

No. All stations are stored on the watch and it does the maths itself. You only need the phone to change settings. The prediction runs until 2056.

How can I see on the watch which station is active?

Turn on “Info line: station and water level”. The watch face then shows the station name and the height next to the next high or low water.

05 · Behind the scenes

How the watch calculates.

The moon and the sun create the tides. Their pull can be split into many regular waves, the tidal constituents. The most important one is M2, the principal lunar tide with a period of 12 hours 25 minutes.
For every station it is known how strongly each of these waves arrives there and how much it is delayed. These harmonic constants come from the TICON dataset of the German Geodetic Research Institute at the Technical University of Munich, derived from decades of tide gauge records.
The watch adds up its station’s waves and adjusts them with yearly factors for the slow cycle of the moon’s orbit. That gives the curve in the graph. High and low water are pinned down to the minute.
Weather, storm surges and river water are not included. Harmonic Tide is therefore a good approximation, but not suitable for navigation.

M2
S2
N2
Sum

Wave	Cause	Period	Strength
M2	Moon	12 h 25 min	135 cm
S2	Sun	12 h 00 min	35 cm
N2	Moon’s distance	12 h 39 min	21 cm
O1	Tilted lunar orbit	25 h 49 min	9 cm

Cuxhaven Steubenhöft: four of the 21 waves the watch uses there, and their sum. Simplified over 24 hours.

Harmonic Tide manual.