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Mike's Muses: Diving with GPS?

Date 9th March 2007

Article by Mike Barrett


Ever since I can remember I have been interested in navigation of one sort or another. Starting from an early age in the boy scouts with an Ordnance Survey paper map and compass I learnt the basic skills of map reading, and navigation.


Over the years compasses became slightly more sophisticated, and then GPS was introduced which could pinpoint your position to within 100 metres. This allowed pretty much anyone to work out where they were with little or no basic skills. This was a real break through for hill walkers, particularly in fog.


The technologies improved allowing the interactive display of map data and GPS position on a PDA. This is where today's SatNav really got started. For me it was Memory-Map that sparked my interest in PDAs as a navigation tool, this was soon added to with Microsoft Streets and Trips, and the initial TomTom application that was bundled with the Navman GPS sleeve.


Looking back five or six years ago we were hardy pioneers of these emerging technologies. We endured frequent crashes, long or no GPS fixes, and the embarrassment of failed demonstrations, but we were safe in the knowledge that this was where the future lay...


I think that the SatNav industry has moved in tremendous leaps over the last three years with the introduction of the original TomTom GO and other PNDs. We now have a mature technology base with lots of potential for expansion, but what are the next moves? Who knows? Each year the industry comes up with some new ground breaking ideas.


Moving away from the Street Navigation market: Marine navigation offers some interesting challenges.


Although you are not restricted to constrictions of road boundaries and rules, there are a large number of other factors to be taken into consideration, not least of which are tides, underwater obstructions, currents and winds. Although in open water you can pretty much plot a course from point a to point b in a straight line it would be rare for you to actually maintain the initial bearing and still arrive at your destination. This becomes even more difficult when your vessel has sails and is powered by the wind. At least under most circumstances though you have confidence when you can see your destination and other reference points on the way.


This brings me to the point of this article, a challenge to the GPS manufacturers.


Last week I was on vacation (a feeble excuse for testing GPS in the Caribbean) when I was literally plunged into a navigation conundrum. I was SCUBA diving and part of the course I was doing was underwater navigation. Well if I thought marine navigation was difficult, trying to do the same underwater is far more difficult.


When you are underwater it is quite easy to lose track of where you are, and where you have been. Previously I have let the divemaster lead the way and I followed. Not so this time, I was the leader, and I had to go right back to basics with a compass.


Actually it is far worse trying to navigate underwater as there are not many points of reference to guide you and often you can get thrown off course by swells, and currents. There is also the added problem of limited visibility, 10 metres is not uncommon, whereas on land you would most often have 10 miles. Underwater it is also a little tricky unfolding an OS map and trying to read that. To my mind this makes underwater navigation far more than a skill. It is a fine and delicate art.


I might point out that I did pass my navigation tests with flying colours, but that is not the issue here. It was a rude awakening having once again to have to use my brain to get around rather than relying on an electronic device.


And there is a lesson to be learnt here: In today's technological age we are starting to forget our basic skills and starting to trust eminently fallible machines. What happens when you rely so much on your SatNav that you no longer pay attention to where you are and where you are going? What happens when the SatNav breaks? Do you have a fall back, and can you still use it?


So finally on to the challenge. You may have guessed what is coming. I am wondering if it is possible to use GPS to navigate underwater. I was half tempted to take my Garmin 60cx down with me, but that is only rated IPX7 so good for 1 metre for 30 minutes. I needed up to 40 metres for 45 minutes or 10 metres for an hour.


Can GPS signals penetrate 20-30 metres underwater? If so can a GPS be built that can withstand the harsh environment of up to 4 times the pressure at the surface, and still work. I know that cameras can with special waterproof housings.


I was initially looking at the problem from a, selfish, recreational diver's point of view. Knowing where you are and where you are going is always a good thing. But if this technology can be made to work then there are a whole host of professional applications that it can be used for.

Coupling precise location data with short or long range transmitters can significantly improve the efficiency and safety of underwater workers, particularly search and rescue divers who often have to work in zero visibility. With this sort of personal tracking a command post will be able to determine exactly where each of the divers are. The swimming patterns used in searching can be analyzed later, and a full record of a search can be made.


I met a New Jersey rescue diver in Australia last year who was telling me that because of the poor visibility conditions he used a special full face mask so that he could communicate with his dive buddy over the radio. This was required as they frequently worked in conditions where there was less that 1 metre visibility. Just imagine how claustrophobic and disorientating that must be.


For companies running dive trips this would also have potential benefits. There would never be any question of "have we got everyone back on board?". If someone did manage to go missing then you would know exactly where they were and could pick them up easily.


For marine biologists the use of GPS underwater could be used to accurately trace out areas of interest such as wrecks or areas of special scientific interest. Going one stage further and linking the GPS data to the dive computer the depth of a waypoint could be accurately recorded. I know that there are sounders and scanners that can perform these functions, but all on the surface, not underwater. This sort of information can vastly improve the records of Marine Biologists.


Getting back to my own personal area of application. I am always fascinated with maps and locational information. I keep hundreds of GPS tracks of boating, cycling, walking and sometimes even driving outings. A few years ago I developed a personal system for geo-referencing pictures taken on my digital camera (long before Sony and others offered these facilities). My utopia would be to know where I am going, know where I have been, and know exactly where I took that magnificent fan coral picture.


Diving with GPS

Now where exactly am I?


Diving with GPS

Navigation on a boat is (relatively) easy.


Diving with GPS

Is underwater GPS Feasible?


Diving with GPS

One of my favorite dive sites in Barbados


Diving with GPS

Here are the GPS tracklogs.


Diving with GPS

Rule 1 stick close to your Dive Buddy


Diving with GPS

We found the boat again.


Diving with GPS

On a different type of dive a boat had to collect us.

So if there is any manufacturer out there wanting to enter a completely new dimension, I am sure that there will be both a recreational and professional market for underwater GPS. And I know someone who is willing to help you develop it... :D


Pocket GPS Contributor

Mike Barrett

Pocket GPS Contributor Website





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