Set your anchor

Missed the moment it dropped? Estimate its position from your boat, or choose it on the map.

Logbook

Completed watches saved in this browser.

A clear view of your anchor

1. Allow location, then tap Drop anchor here when you drop it.
2. Tap the swing distance to size your circle. A tap changes it by 1 m; holding repeats.
3. Start or resume your watch. Keep this page visible and test your sound.

Know what is being monitored

GPS tolerance is the largest reported position uncertainty accepted for monitoring. Automatic uses 40% of your swing radius, capped at 25 m. A larger tolerance admits less precise fixes. Positions older than 20 seconds are not used.

An outside-circle warning requires fresh, distinct GPS fixes over at least two seconds, with the reported GPS uncertainty also outside the circle. Poor GPS shows “Monitoring degraded”; it cannot reliably confirm a boundary crossing.

This browser preview cannot provide a dependable overnight or background safety alarm. Wake lock and audio depend on your browser and device settings. Closing the page or restarting your phone stops monitoring. Your anchor is saved, but you must reopen and resume with fresh GPS.

Maps and depth

Standard maps use OpenStreetMap; satellite imagery uses Esri. WA seabed adds Landgate regional bathymetry where available. It is a seabed reference, not a current nautical chart, tide-corrected depth or depth under your boat. C-MAP is not connected.

Privacy

No account is required. Anchor coordinates and completed watches stay in this browser's local storage. Clearing website data deletes them. Map providers receive your IP address and the map area requested. Demo data is kept separate from your real anchor and logbook.