Anchor! helps you to detect a dragging anchor

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The Anchor! app handbook

Main view presentation

This is the position of your anchor on the Map. 

Anchor location drag and drop :

Most skippers do not set the alarm while lowering the anchor. However, it is more appropriate to center the alarm on the actual anchor position. Anchor features the unique possibility to move the anchor position. 

As for all anchor applications, if you are in the cockpit, the cockpit position will be recorded instead of the anchor position in the front of the Boat. You could enhance the anchor location precision by setting the anchor from the windlass position.  Moving the anchor on screen with drag and drop seems a better idea.

Alarm distance: 

This is the distance from the "anchor position" as set on the map at which the alarm will be triggered. You can ajust this distance from the map view or the settings view. Usually I put the chain's length+5m.

A red circle shows the position on map where the alarm is triggered. You can adjust the circus radius by touch on the red disk.


The path of the boat is shown on map. The color of the path slightly evolves with time to allow you to discriminate older locations. If the anchor holds correctly, the most recent tracks will be above the older ones.

Auto zoom: 

The app automatically set the zoom level according to the alarm distance and your speed. You can also zoom freely on the map.

Map view buttons

Use the LOWER button to set the anchor position in the current location. The adequate moment to push the LOWER button is while lowering the anchor.

Use the RAISE button to disable all alarms and before lowering again: The adequate moment to push the RAISE button is while raising the anchor.

Changing position and center:

The locate button enables Tracking mode: the map is centered on the current location and follows the device. Track mode can be disabled either by deselecting the locate button or by moving the map, In tracking mode, the aiming circle turns blue.

Center the map at the anchor location. 

The compass button enables or disables Heading mode. In Heading mode the compass turns to point to the North. 

The orientation of your device is shown under the compass needle, in heading mode the Hull is pointed up.

When Heading mode is available and disabled, the map is either aligned with North up or turned by you.


When an alarm is triggered, you will be prompted to stop the alarm for 15s. You can then disable the alarms, change the alarm radius or the anchor position as you see more fit. After 15s, the alarm will run again if it is enabled and triggered.

Ring alarm: 

An alarm noise will be triggered when the current distance from the application to the anchor recorded position is more than the alarm distance. You can activate the alarm from the Map, Anchor and Settings views. The alarm status is shown on the map view.

Accoustic alarm button when disabled.

Accoustic alarm button when triggered.

Visual alarm: 

A visual warning will be triggered when the current distance from the application to the anchor recorded position is more than the alarm distance. The visual warning is blinking to attract attention. You can activate the alarm from the Anchor and Settings views. The alarm status is shown on the map view.

Visual warning is effective only when the app is runned in foreground.

Visual alarm button when disabled.

Visual alarm button when trigerred.

Mail alert:

You can also receive an alert by mail. The app will alert you by sending a single email to the address of your choice.

Other views


The Settings view allows you to set or unset the visual and ring alarms. 

A slider allows you to set the alarm distance.

The Settings view also displays your location's GPS coordinates. 

Furthermore, when anchored, the anchor position and the distance in meters from anchor to the device are also shown.

Help view:

Anchor ! is very easy to use, but in case you have any doubt on its usage while at see, the full documentation is included in Anchor! and available offline.

Last tips

Accuracy: it is recommended to lauch the app a few minutes before anchoring, so that the accuracy builds up.


When you have no GPS signal, this icon is  shown. 

Check that you are not that plane mode is disabled  and that localisation services are enabled for Anchor!

Battery usage:

This application require precision positionning. Precision positionning drains the battery quickly. Once in background, the localisation is stopped is no anchor is set. However when an alarm is active, even in background Anchor! will track your position to notify you if you leave the anchor perimeter. If you intend to use the app for a long time, put your device on charge.


The app use the maps provided with IOS. These maps are clearly not nautical charts: do not rely on them for navigation. Check reliable charts for depth contours while anchoring.

Remote mode - iPad 


Landscape mode - iPhone


Settings view - iPad


Settings view - iPhone


Remote mode - iPhone


Visual Alarm - iPhone

(white/black blinking eyecatcher)


Map mode - iPhone

(c) A. Arnail 2013