Anchor alarm

Set a swing radius around your anchor and Guardian watches your position against it — sounding the boat and alerting your people the moment you drag.

Dragging anchor is the failure every sailor plans around: it happens at night, in weather, and the first sign is usually the wrong one — a neighbor's horn, a change in the boat's motion, a depth alarm. Guardian's anchor alarm replaces "sleep with one eye open" with a watch that never blinks: your GPS position, checked continuously against rings you set around the anchor.

Two halves: aboard and away

  • Aboard (free on every plan): with the app open on the boat, the local anchor alarm runs entirely on your device — a siren and an alarm entry the moment you're outside the ring. Like the in-app Flooding Sentry, it needs no plan and no internet.
  • Away (the cloud watch — Weekender and Cruiser): the Guardian cloud keeps evaluating the positions your boat reports even with every phone asleep, and pushes a drag alert to everyone on the vehicle. Cruiser can escalate a drag to SMS Not live yet.
How the anchor watch's two rings work ⚓ your anchor — the center of the watch normal swing on the rode ⛵ ⛵ ⛵ Warning ring a heads-up as you approach the edge — time to look, not yet an emergency Alarm ring outside it (beyond GPS accuracy, or two fixes in a row) → the drag alarm fires: siren aboard, push to everyone on the boat Swing back inside and the alarm resets itself — no stale alarms to clear. Arming requires a live GPS fix — Guardian refuses to watch blind against a stale position.
Two rings around the anchor: the warning ring buys you a look outside; the alarm ring wakes the boat. Set the radii to match your rode and swing room.

Setting it up

  1. Give the boat a live position. The alarm needs a real GPS feed — a GPS source: your cellular router's built-in GPS, an NMEA feed, or this phone. A manually pinned position can't drag, so Guardian refuses to arm an anchor watch against one.
  2. Anchor, then arm. From the Location page, arm the watch at your current position — that fix becomes the center.
  3. Set the two rings. The inner warning ring gives you a heads-up as you approach the edge; the outer alarm ring is the line that fires the drag alarm. Size them to your rode: swing room plus a margin for GPS scatter.

How the alarm decides

GPS jitters, and a good anchor alarm can't cry wolf. Guardian fires when your position is outside the ring by more than the fix's own accuracy, or when two consecutive fixes land outside — so one noisy reading doesn't wake the boat, and a real drag doesn't wait. The alarm is rising-edge (it fires once as you cross, not continuously) and resets itself if you swing back inside.

The stale-feed rule: if the position feed goes quiet for ~5 minutes, Guardian warns you instead of pretending to watch. An anchor alarm that's silently blind is worse than none — you'll always know which one you have.

Who gets alerted

Aboard, the siren wakes the boat. On the cloud watch, the drag alert pushes to everyone the vehicle is shared with — your partner in the next bunk, crew ashore, the friend keeping half an eye on her. See Sharing & roles for how people join a vehicle.

Coming soon Friends will extend this further: notification-only contacts (no dashboards, no controls) who can receive anchor-drag alerts — on every plan, including Dockside. Details on the roadmap.

Anchor alarm vs. security zone

They share the same jitter-resistant logic, but answer different questions. The anchor alarm asks "are we dragging?" while you're aboard or anchored out — centered on the anchor, armed against a live fix. The security zone asks "did it leave without me?" while the vehicle is parked or slipped — centered on where it belongs, and happy with a manual pin because it's the vehicle's feed that proves it moved.

Location, security zone & presence →