Reading a tide table

A tide table looks like a wall of times and decimals. Once you know what the numbers are measured from, it reads easily.

Times and heights

Each line is a turning point: a high or a low, the time it happens, and the predicted height of the water. Around Singapore you usually get two highs and two lows a day, and the two lows are often quite different in height. One may barely uncover anything while the other drains the flats.

Measured from where?

Official tables give heights above chart datum, a level set low enough that the water rarely goes below it. That's why the numbers are almost always positive, and why guided walks talk about tides "of 0.5 m and below".

This site doesn't use chart datum. My predictions come from tide-gauge records measured against the gauge's own reference, so I show heights relative to mean sea level instead, which is why you'll see negative numbers here. The two scales differ by a fixed offset that I don't publish. To compare with a guided walk's threshold, look up the same day in the official table.

The ratings

Rather than ask you to translate heights, the calendar rates each low against all the others in the two years it covers: excellent is the lowest 5% of low tides, good the next 10%, and fair the next 15%. Everything else isn't shown on the overview. Each low is also marked by whether it falls in daylight, twilight, or the dark.