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View Poll Results: Blue Water- is a Sextant Necessary?
Absolutely essential 24 18.90%
Desirable, but not essential 52 40.94%
Good fun, but little practical use these days 39 30.71%
Don't waste your money and time on this 11 8.66%
Sextants make excellent dingy anchors. 3 2.36%
Multiple Choice Poll. Voters: 127. You may not vote on this poll

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Old 06-11-2012, 14:38   #166
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Jim, you mean the lunar landing wasn't filmed on a sound stage in Culver City?? Or maybe near Roswell with the aliens as advisors?

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Old 06-11-2012, 14:58   #167
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Re: Poll-Blue water. Is a Sextant Necessary?

I don't think it makes sense to be anti-GPS, and I don't recall coming across any posts in this thread which struck me as such.

Nor does it seem to make much sense to be anti-sextant.

I don't understand why the discussion seems to keep re-polarising.


I think the analogy of GPS with motors, and sextants with sails, has some merit.
Of course it also has limitations.

What it does illuminate for me is that it makes sense to some people to have both.

But a majority of boaters do not seen any benefit in sail: it's dated or archaic, it requires considerable effort and knowledge to get good results, and even then it's slow, inconvenient, inaccurate and expensive. So it goes with sextants.

However circumstances alter cases. If you plan to spend years at a remote, uninhabited location, it might not make much sense to have a motor; once you run out of fuel, it's useless deadweight.

Similarly, in such circumstances, the usual attractions of a GPS-only vessel start to dim a little. Repair or replacement is not possible. The hand-held backups rely on dry batteries which do not have unlimited shelf life.

- - - -

Another aspect of this analogy: if you get any sort of kick out of motors, then they're a great backup to a mainly sailing vessel.

And vice versa: if you love aspects of sailboat rigging and repair, it might be a good option to have a small steadying rig, sufficient to get you home, on a predominantly motor boat.

But in each context the choice of this backup is optional, not necessary.

A person who loves motors and doesn't have any affinity for sail should perhaps think about an auxiliary backup propulsion motor. This should not be construed as 'anti sail'.

Conversely a person whose blood does not quicken even slightly when a motor catches on the first spin of the flywheel and burst lustily into life, might be better served by concentrating elsewhere for backup options: sweep oars for getting into and out of windless anchorages, spare rigging and materials for constructing a jury rig, a comprehensive set of sails for all circumstances, etc etc.

They're going to make a better job of the planning and the implementation, and a deeper level of understanding, than for an option for which they really have little enthusiasm.

It's pointless trying to talk people out of their position on this spectrum, unless you consider that you understand their circumstances (and the relevant options, and the rationales for their choices) better than they do.

So for me the purpose of this thread is for people to voice their rationales, in context.

That's potentially useful for people currently elsewhere on the spectrum.

For instance, while I'm hugely impressed by the technology and performance of GPS, the detail has never captured my imagination.
So I learn a lot from people explaining pros and cons.
Most recently from n77, pointing out issues with loss of almanac data in a handheld which has been turned off for a long period, and warning about SD only (I didn't know there was such an option, in fact I hadn't heard of SD). It will be obvious to all that he wasn't attacking GPS, he was helping people to understand how to use it.

In the more general case, pointing out limitations is not necessarily an attack, but it is a valid part of explaining why a particular choice suits particular circumstances better.

And I wish those reading would hesitate before rushing to defend something which, more often than not, is not under attack.
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Old 06-11-2012, 16:46   #168
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Re: Poll-Blue water. Is a Sextant Necessary?

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Originally Posted by goboatingnow View Post
...
Its worth noting that during desert storm the US moved the GPS constellation to provide better DOP figures as the US military didnt have enough military ( P code) receivers and relyed on 000s of civilian receivers. This isnt the case today, the constellation is sufficient and more P code receivers are around. Thats is what many users especially in the altantic saw as a poorer DOP figures or some degradation in accuracy during that time,( 16 Block II birds were active at that time).

Dave
So, could this repositioning of the GPS constellation have caused the outage we experience in route to Bermuda? (See my earlier post on this thread)

To address a previous comment: All the hand-held units had been used and tested prior to the crossing and some during. Even when reset they could not find a signal. The chart plotter had been running continuously since we left Mass. All units were able to re-acquire after making land fall in Bermuda.
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Old 06-11-2012, 22:33   #169
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Re: Poll-Blue water. Is a Sextant Necessary?

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Originally Posted by Andrew Troup View Post
I think the analogy of GPS with motors, and sextants with sails, has some merit.
Of course it also has limitations.

What it does illuminate for me is that it makes sense to some people to have both.

But a majority of boaters do not seen any benefit in sail: it's dated or archaic, it requires considerable effort and knowledge to get good results, and even then it's slow, inconvenient, inaccurate and expensive. So it goes with sextants.

However circumstances alter cases. If you plan to spend years at a remote, uninhabited location, it might not make much sense to have a motor; once you run out of fuel, it's useless deadweight.

Similarly, in such circumstances, the usual attractions of a GPS-only vessel start to dim a little. Repair or replacement is not possible. The hand-held backups rely on dry batteries which do not have unlimited shelf life.

- - - -

Another aspect of this analogy: if you get any sort of kick out of motors, then they're a great backup to a mainly sailing vessel.

And vice versa: if you love aspects of sailboat rigging and repair, it might be a good option to have a small steadying rig, sufficient to get you home, on a predominantly motor boat.
The analogy, while emotive, does not work because boats with sail generally only have one engine, so a back up propulsion system is invaluable.
Multiple GPS receivers can be carried, many with their own battery supply.

A boat with 5 or 6 independent engines, with several different fuel sources, would not see the need for an other system especially when there are no cost savings.
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Old 07-11-2012, 00:24   #170
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Re: Poll-Blue water. Is a Sextant Necessary?

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Originally Posted by Andrew Troup View Post
I don't think it makes sense to be anti-GPS, and I don't recall coming across any posts in this thread which struck me as such.

Nor does it seem to make much sense to be anti-sextant.

I don't understand why the discussion seems to keep re-polarising.

And I wish those reading would hesitate before rushing to defend something which, more often than not, is not under attack.
Maybe it's just me...but I'm not seeing how this topic is or has been anti GPS or Sextant. Or even polarized or attacked. It's just opinions. I think we all have a GPS or two and a few of us like the fun, beauty, challenge and feeling of independance of a Sextant
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Old 07-11-2012, 00:33   #171
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Re: Poll-Blue water. Is a Sextant Necessary?

Noelex 77

I'm not sure you understood my point.
I'm talking in the abstract, using an admittedly imperfect analogy as a discussion tool.
I'm talking about a person with a predominant preference for one of two choices, one low-tech, self reliant and old-school, and the other high tech, outsourced and modern.
I'm saying there will generally be benefits from putting a foot in the other camp, but that in particular special cases there may not.

With respect to your first paragraph, I'm not sure that the number of feet one chooses to place in either camp has any bearing on the point I was trying to make.

Perhaps you thought I was trying to make some other point?

I'm also not sure why you added the sentence about multiple GPS receivers "with their own battery supply" - I'd already covered that in my post, but given an instance of a circumstance which might invalidate that strategy.

I also instanced another situation where putting all your feet in the ''outsourced" camp did not make sense, but perhaps I was uncharacteristically brief.

A sailboat spending five years in South Georgia would have little enough use for one engine, let alone five. There are plenty of interesting parts of the world which do not offer fuel deliveries. Unless one of your multiple sources of fuel is indigenous.... seal blubber, perhaps?


Luckily there is often no shortage of wind in such places.

This is a very special case, but that's my point. Circumstances alter cases.

To me a recreational power boater is also a special case, diametrically opposite in many ways, where reliance on a single well-maintained engine makes sense, with a cellphone for backup (and a paddle as a token foot in other camp!).

It happens to be a case which has no appeal for me, but 5 years in uninhabited glacier country clearly has a lot less appeal to the majority of humanity.


I certainly don't understand your point, on this occasion. What do you mean by the first sentence ? I'm not sure how to link "a backup propulsion system is invaluable?" to the preceding contention.

I don't understand how it invalidates the use of my analogy, in the limited and abstracted way that I used it.
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Old 07-11-2012, 00:37   #172
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Re: Poll-Blue water. Is a Sextant Necessary?

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Maybe it's just me...but I'm not seeing how this topic is or has been anti GPS or Sextant. Or even polarized or attacked. It's just opinions. ...
I don't see attacks or people being anti GPS or Sextant either. Certainly not in any way which merits reply.

What I am seeing, and not understanding, is people being unnecessarily defensive of one or the other.
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Old 07-11-2012, 01:50   #173
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Re: Poll-Blue water. Is a Sextant Necessary?

what I was saying is that there are quite a few posts in this debate that seek to retain sextant use, based on a fear of failure of the GPS network or the on-board equipment. Real world experience has shown that this isnt a valid argument. Keep using a sextant, because you like using it, but its not a necessity if you dont what to use it.

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Old 07-11-2012, 12:39   #174
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Risk Management

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what I was saying is that there are quite a few posts in this debate that seek to retain sextant use, based on a fear of failure of the GPS network or the on-board equipment. Real world experience has shown that this isnt a valid argument. Keep using a sextant, because you like using it, but its not a necessity if you dont what to use it.

Dave
 
I'm writing this from a location where no earthquake has been recorded in human history, and where the risk is incalculably low. Nevertheless, buildings have to be built to resist earthquakes, which makes them considerably more expensive.

This is worth doing, not because it's likely to happen, but because the consequences if it does happen are so serious.

If someone were to pretend that the risks of inability to fix position by GPS can be reduced to zero, that simply indicates they don't understand technology or probability.

I don't have a problem with someone who says that, for them, the risks are so low that they're happy to live with the consequences. But it becomes a problem when they try to make a more general claim on behalf of others, or to say that their assessment is not valid.

Risk management means taking both probability and consequentiality into account, and (in an unregulated environment like cruising) everyone makes up their own mind on that, having regard to their own situation and their degree of tolerance of risk.
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Old 07-11-2012, 14:14   #175
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Re: Poll-Blue water. Is a Sextant Necessary?

I don't feel the "earthquakes may happen" is a good comparison. If you lose your GPS fix out in the open you are just basically lost and you chose a direction based on the Sun and sail till you get somewhere (predates sextants I believe).

Regardless of what past posts say, including mine; I don't really care if YOU want to have a sextant! Just like I don't really care what boat YOU want to sail on.
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Old 08-11-2012, 04:54   #176
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Gosh Don, a few years ago there was a national poll in the States, and some large fraction of respondents said they didn't believe that the Moon landings were real. I won't get into how many folks believe that the universe was formed around 6000 years ago over a period of seven days... so do you really think that this number (84%) has any real meaning?

But seriously, I suspect that the 84 % that you note is closely equal to the percentage of respondents who never really sail offshore. For coastal or harbour sailing, many of us who do carry sextants and know how to use them would agree that they are not necessary.

Cheers,

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I think the corallary is the opposite - a small fraction think the moon landings did not happen. A smaller fraction think sextant is necessary. A smaller fraction think OJ was innocent. just so we all agree who is in the minority here.

it is crazy but my observation is there is always 20-30% of the people that vehemently defend a minority position. Human nature to argue I guess...
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Old 08-11-2012, 04:58   #177
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Quote:
Originally Posted by goboatingnow
what I was saying is that there are quite a few posts in this debate that seek to retain sextant use, based on a fear of failure of the GPS network or the on-board equipment. Real world experience has shown that this isnt a valid argument. Keep using a sextant, because you like using it, but its not a necessity if you dont what to use it.

Dave
well said...

you wont die if you dont have a sextant...

hundreds of crossings are made every year with no sextant. I am still waiting for, "Has anyone seen S/V Really Lost. Tried to cross the pacific with no sextant, only 3 gps' and hasn't been seen since January."
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Old 08-11-2012, 11:45   #178
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Re: Poll-Blue water. Is a Sextant Necessary?

Thank you both.

You appear to be channelling the ironic powers of Mark Twain, and in doing so you've illustrated a couple of my points more graphically than I ever could.
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Old 08-11-2012, 11:55   #179
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Re: Poll-Blue water. Is a Sextant Necessary?

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Originally Posted by goboatingnow View Post
what I was saying is that there are quite a few posts in this debate that seek to retain sextant use, based on a fear of failure of the GPS network or the on-board equipment. Real world experience has shown that this isnt a valid argument. Keep using a sextant, because you like using it, but its not a necessity if you dont what to use it.

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Old 08-11-2012, 11:56   #180
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Re: Poll-Blue water. Is a Sextant Necessary?

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Jim, you mean the lunar landing wasn't filmed on a sound stage in Culver City?? Or maybe near Roswell with the aliens as advisors?

Dave
Back in the 70's as a kid I recall seeing a documentary showing that the landing was faked. Capricorn something?
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