Anchor Alarm 219

GPS Anchor Alarm, Anchor Watch and Danger Ahead Alerts

Anchor Alarm 219 is a maritime safety app that provides GPS anchor-drag monitoring, anchor-watch functions and Danger Ahead alerts for boats.

A one-time in-app purchase unlocks the full version. No subscription is required.

Anchor monitoring

While the vessel is anchored or moored, the app monitors its GPS position and continues monitoring in the background after the anchor alarm is started.

If the vessel moves outside the selected safety area, the app sounds an onboard alarm and can send an SMS warning of possible anchor drag or unauthorized vessel movement.

For remote SMS alerts, the monitoring phone must remain aboard the vessel, powered on, with GPS and mobile service available.

Danger Ahead alerts

While underway, Danger Ahead monitors the area in front of the boat using NOAA-derived nautical chart and depth information. It warns when shallow water, shoreline or a charted obstacle is detected ahead.

Danger Ahead is available in U.S. waters only and requires an internet connection.

Core features

• GPS Anchor Alarm: Monitors the vessel and detects movement outside the selected safety radius.
• Anchor Watch: Continues monitoring while the app is running in the background.
• SMS Safety Alerts: Sends an alert to a user-selected phone number when anchor drag or GPS loss is detected.
• Danger Ahead: Warns of shallow water, shoreline and charted obstacles ahead.
• GPS Accuracy Filtering: Uses multiple GPS samples and rejects inaccurate readings.
• Two Anchor Setup Methods:
– Over Anchor: Hold the phone over the bow and tap when the anchor reaches the bottom.
– Bearing to Anchor: Align the vessel with the anchor line and tap Set, preferably using the boat compass.
• Manual or Automatic Heading: Enter the anchor bearing manually or obtain it using the phone or boat compass.
• False Alarm Adjustment: Adjusts the allowance following a false alarm to reduce repeated alerts.
• Activity Logs: Records anchor status, vessel movement and alarm events.
• GPS Loss Alarm: Sounds an alarm and can send repeated SMS alerts if GPS is lost during anchor monitoring.
• NOAA Nautical Charts: Displays vessel position, anchor location and alarm settings. U.S. waters only.
• NOAA Tide Information: Displays predicted and observed tide information graphically. U.S. waters only.
• Markers and Measurement Tools: Save chart locations and measure distances.
• Anchorage Search: Links to Navily on supported phones.
• Boat Position Display: Shows the vessel, anchor bearing, safety circle and previous positions.
• Last Anchor Status: Displays the most recently recorded position and monitoring information.
• Automatic Allowance: Adjusts the safety margin for GPS variation, vessel movement and anchor resets.
• Built-in Help: Explains the app’s settings and features.

SMS and privacy

The SMS alert number is entered voluntarily by the user on the Setup screen. It is stored locally on the user’s phone and can be changed or deleted at any time. To send SMS safety alerts, the app requires SMS permission. The user is asked to grant this permission each time a phone number is entered or changed on the Setup screen.

The app uses the number only to send requested safety alerts. It does not transmit the entered alert number to the developer or use it for advertising or promotional messages.

Permissions

• Location: Monitors vessel position and movement.
• SMS: Sends user-enabled anchor-drag and GPS-loss alerts.
• Notifications: Displays monitoring status and safety alarms.
• Internet: Accesses NOAA charts, tides and Danger Ahead information.

Important safety notice

Anchor Alarm 219 is a support tool and must not be used as the sole navigation, collision-avoidance, grounding-prevention or anchor-watch system.

NOAA chart and depth information may be incomplete, inaccurate or outdated. Always maintain a proper watch, verify water depth, use appropriate navigation equipment and maintain backup alarms.

Recent changes:
New feature to improve alarm accuracy based on the boat's movement as it swings around the anchor.
Added help for calculating the chain to let out when anchoring.