This app alerts you 30 seconds before you enter over the sea charts 3-meter curve. It also functions in background in the pocket or in a strap on the arm. When the app is on, the camera image is used to display areas in the charts 3-meter curve with transparent red polygons.
The 3-meter curve is provided by the Mapping Division of the sea and refers to depths in relation to the 0-level for depths in charts (sea charts). The app is intended to be used on phones and tablets with forward facing cameras. Attached to the window and directed forward, the app displays camera images with stored NoGo areas (areas of depth less than 3 meters at low tide) in transparent red. A "course vector" points in front of the boat in the course direction. The length of the vector is configurable, in the default option it is set in 30 seconds.
The phone can also be held by hand to view the No-Go areas surrounding the boat. The quality of the phones compass then determines how accurate the display will be.