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    Re: Dependence on GPS
    From: Lu Abel
    Date: 2009 Nov 01, 10:20 -0800
    Peter:

    I've seen some themes in replies to your posting:  (1)  First and foremost, good navigators use ALL available information and techniques to assure a safe voyage.   To eschew any particular technique (eg, GPS because "it can't be trusted") is as silly and dangerous as to eschew any other technique (eg, DR because I'm too lazy and/or trust the electronic box too much to do it).   (2)  There are technologies to keep GPS sets working under pretty adverse conditions (eg, waterproof bags, even waterproof metal cases).

    My understanding of  your point of view would be helped if you would provide the brand names and models of these GPSs that failed you. 

    I have difficulty believing that a contemporary GPS set would fail as easily as you claim.   For example, the commonplace Garmin 76 series is rated IPX7 for waterproofness.   To gain an IPX7 rating a unit must withstand being submerged to a depth of 1 meter for 30 minutes.   That seems a heck of a lot more stressful than the occasional splashing a unit might get on a small boat or kayak.  (I'd also note that handheld radios, which one poster mentioned carrying, are also rated IPX7, so how can he trust his handheld to work reliably while not trusting a GPS?)

    As for battery life, the rated battery life for a Garmin 76 is 16~18 hours.  We all know battery capacity is reduced in the cold, so maybe it's less in a cold, water-soaked environment.   But "chewing through at an unsustainable rate?"   First of all, I use a 12v accessory cord off my boat's 12 v electrical system.  AA cells are suddenly replaced by a 90 lb lead-acid golf cart battery that's pretty hard to "chew through"   But even suppose I didn't have an accessory cord?   The Garmin 76x series of hand-held GPS sets will give a fix within one minute of turning on.   Let's say I was doing a trans-Atlantic voyage, which takes about 30 days.   I could get a fix every three hours and still have plenty of life left in the original set of batteries when I hit the other side of the pond.  I wouldn't have had to open a single one of the heat-sealed waterproof packages of batteries that, as a prudent navigator, I had carefully stowed about the boat.

    In the early 1990s when GPS handhelds first became available I remember attending a talk by a Magellan representative.  He brought a military GPS set with him and demonstrated that it was identical to the civilian model except (a) it was olive-drab instead of yellow and (b) one of the buttons on the keypad was different -- in the military unit it was painted bright red and labeled "Target."    The rep demonstrated the ruggedness of the unit by repeatedly dropping it on the floor -- "took a licking and kept on ticking"

    I truly believe you have had some bad experiences with GPS.   But without more data on the exact details I have very hard time accepting a generalization to "GPS is an inherently unreliable navigation tool."

    Lu Abel

    Peter Fogg wrote:

    Frank writes:

    If you're going to claim that those waterproof bags are just another technology waiting to fail, then you have to apply that same standard to traditional methods of navigation. Do you store your chronometer in a waterproof bag? How about your spare chronometer?

    Sure.  These may be good ideas.  Over time the watches that are less waterproof fail to proceed and get replaced.  The aim is to have back-up systems, ideally ones that can perform the same useful functions as those being backed-up, but not vulnerable in the same ways.  So motors to augment sails, oars to function in the place of recalcitrant outboards, kerosene (paraffin) lamps in case the electricity supply goes (or just to preserve battery power), tinned food if the fish don't bite, and so on.  Traditional methods of nav for when the GPS has an issue.  Nah, forget that one.  Nav is a whole mindset, not just an alternative methodology.  Its about being aware, in a wide sense.

      So what to do... carry a cheaper handheld GPS that you can turn on when the main system fails.

    Frank, Frank.  Impractical in practice.  Those things take quite a while from cold to become functional, then continue to chew through those little AA or even worse AAA cells at a quite unsustainable rate.  You couldn't carry enough cells to cross an ocean with.  They are only for occasional use, assuming the nearest Wal Mart is always close-by.  Yes, you could use rechargeable cells, with a solar system to do that, and then you have another system to maintain while you wait for it to fail.  I'll say it again, sailboats provide terrible environments for even robust equipment.  Sailing involves a lot of fixing stuff or learning to do without it.
     
    Let me ask you this: if you met someone planning on doing some long-distance sailing, and they said to you, "I'm planning on taking a carefully stored handheld GPS for backup in case the main satnav system fails", would you advise AGAINST taking that backup GPS?? Do you not agree that the very great majority of the cases where the main satellite system fails can be answered simply by breaking out the spare and using it properly?

    I think this person would be much better advised to learn to navigate, and not be dependent on electronics to do it for him/her.  

    Let's remember that the basis of nav is a DR plot.  Knowing where you start from, then tracking movement over time.  Everything else is just ways of checking that plot.  This is the real reason why GPS is so potentially dangerous - when it fails, or the necessary supporting systems fail to allow it to do its miraculous stuff, then the poor silly sod has no idea at all, instead of having quite a useful idea that is regularly updated, albeit a derived position that can probably stand some refinement.  Dependence on GPS doesn't encourage people to look carefully at their environment on an ongoing basis and think constantly about how what they see can be useful information.  Traditional nav does this.




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