Open it
Tap a spot, then Hour by hour, then Anchor here. Or open the panel and tap Anchor math for your position.
Work it out
- Enter the depth from your sounder. Until you do, it estimates from NOAA's elevation model, which is coarse.
- Choose how long you're staying: Tonight, 1 day or 2 days.
- Choose a scope: 3:1, 5:1 or 7:1. You see the chain for each.
Chain to let out = (deepest water during your stay + bow roller height) × scope.
In the picture: 27 ft at the highest tide plus a 4 ft bow roller is 31 ft, and 5 times that is 155 ft.
What else it tells you
- Deepest and Shallowest: the water at high and low tide during your stay, and when.
- Under the keel: what's left at low water, using your draft.
- Swing room: how wide a circle you'll need.
- Most wind and Most current: what's forecast while you're there.
- Tide during your stay: the curve, with every high and low.
If the chain is more than you carry, it says so. If weather is forecast to build, it suggests more scope. Set your boat's details once in Settings.
This is a starting point, not a guarantee. Your bottom, your anchor and the weather all matter. Set it and check it like you always would.
Common problems
It says the tide hasn't loaded.
It may still be loading, or there may be no tide station within 15 nm. Until it loads, the numbers don't include the tide, so don't rely on them.
The chain is far more than I expect.
Check that you entered a sounding. The chart estimate can be well off, and a deep spot needs a lot of chain.
Next: Underway alerts