Underwater GPS positioning made easy
The solution for underwater position logging.
Gramper GPS buoy, for divers, developed by divers.
What it is
That is exactly what it is for. Up on your reel, a GPS fix at the surface, and back down. The position is on the card in your hand.
The magnet in your glove is the only control there is. One lamp tells you what it is doing.
The buoy on its way up. The diver has not moved.
Why carry one
The buoy goes up on your reel, takes the fix and comes back down. You are still on the point you wanted to mark.
The surface
Three readings every time it surfaces, each with its own HDOP value. The software discards the ones that are too high, and what is left is accurate to two metres.
Light tension on the reel is what holds the buoy upright and closest to where you actually are. If it has drifted it shows up in the data as a line, and the position can still be calculated from it.
The magnet in your glove is the only control there is — no button to find with cold hands — and nothing about marking a point takes you off the bottom.
The bottom
You are on it now, and the alternative is a compass bearing and your memory of the swim out. Unclip the reel, send the buoy up, and the position is on the card before the dive is over.
Mark it and carry on; the salvage can happen another day. Ninety-nine positions fit on one card, each stamped with the date and the time in UTC, so work spread over a season stays in order.
After the dive the card goes into a computer: one CSV per location, three readings each with their HDOP value. Convert them at gpsvisualizer.com and the whole site opens in Google Earth, named point by point.
How it works
Calm weather and zero current give the best results. If the buoy has been drifting it shows up as a line, and you can still calculate your position from it.
On the point that matters. The magnet in your glove to the sensor under the lid — there is no button to press with cold hands.
It blinks red while it acquires. A cold fix takes about two minutes, a warm one under twenty seconds.
Off the reel on a light tension, which is what keeps it upright and closest to the position it is logging.
Green means the fix is on the card. Ninety-nine of them fit, each stamped with the date and time in UTC.
Order
By Karst Braaksma and Leon van Kesteren. One price, one buoy, complete.
€300
