Landlubber
Landlubber teaches underwater compass navigation by having you walk the patterns on dry land, with the phone acting as referee: it reads your heading, counts your steps, and shows you the shape you actually walked.
No — that is a real magnetic effect and it is worth knowing about. Reinforced concrete, wiring, steel furniture and vehicles all bend the field a phone's magnetometer reads, exactly as they bend a real dive compass. It is the same reason you keep a compass clear of your tank valve. Take heading scores outdoors, away from cars, before trusting them.
An exam is scored on how far you finish from where you started, so it needs a GPS fix. Indoors there is no distance to be wrong by and a pass would mean nothing. Step into the open, the lamp turns green, and the start button appears on its own.
Steps are detected from the phone's accelerometer, which is good to within a few per cent at a steady walk. Hold the phone reasonably still, walk at a natural pace, and it will track you closely. In tutor mode it ticks on every step it sees, so you can feel whether it agrees with your count without looking at the screen.
Forty steps or more. GPS is good to a few metres, so a very short leg cannot be scored honestly — the error in the measurement would be a large share of the leg itself. The app shows its own confidence beside the closure figure for that reason.
No, and it is not intended to. Buoyancy, trim, task loading and the disorientation of poor visibility are absent on dry land, and they are most of what makes underwater navigation difficult. What it replaces is the guesswork in the debrief: it shows which leg went wrong, which the water never does.
Open the app, go to Unlock and choose Restore Purchase. Purchases are tied to your Apple or Google account, so a new phone signed into the same account will restore them.
Please do — it was built to be set as homework between the classroom session and the first dive. Write to [email protected] and we will sort out promo codes for your students.