About CoastFinder

Point your phone at the sea and CoastFinder names every island, lighthouse, shipwreck, shoal and reef in front of you, with distance and depth.

Mountains have had this for years: hold up a phone and every peak on the skyline is named. The coast had nothing of the kind, and there is a reason. Almost everything worth naming on the water is low or underwater. From a beach, the curve of the earth hides nearly all of it, so an app that labelled only what you can see would show an empty sea.

CoastFinder draws what the curve hides instead of deleting it. Hidden features are drawn faintly and marked below the horizon, with their true bearing and distance, and submerged ones carry their charted depth and an estimate of the depth right now. Nothing is recognised in the picture. The app knows where you are, which way you are pointing and where every charted feature sits, and works out the rest.

Where the data comes from

Positions and depths come from public sources: NOAA charts and wreck records, the US Coast Guard Light List, the North and South Carolina artificial reef programs, NOAA tide predictions and OpenStreetMap. They are not invented. The full list is on the Data sources page.

Every feature records which source its position came from and how far off that position could be. A surveyed light is good to a few tens of metres; a wreck position from an old loss report may be out by kilometres. Where two sources disagree and nothing settles it, the feature is marked as disputed rather than quietly picked. When the app is unsure enough that it matters from where you stand, it draws a span instead of a point, so you can see the doubt rather than be misled by a precise-looking label.

Built in North Carolina.