gps for the celestial navigator

[jpfx]

hello everyone, first post here though I've been lurking for a while.
For some reason I've got it into my head that I would prefer to navigate (when that day comes) using sextant and nautical almanac. However I still want to carry a gps onboard.
I've been scanning for a suitable model of the 'track plotting' variety which I think contains everything I want and nothing I don't, specifically no charts. The models are:

furuno gp32
furuno gp33
si-tex gps 90
garmin 152h

Does anyone have any experience with these devices?
What I'm looking for is mostly is ease of use, low power consumption, simple way point entry, day & night clarity.
I realize this doesn't make any sense to 'most' people. In fact, I did buy a raymarine A57D and test mounted it on my current boat (rob roy 23). It looked out of place to me. It probably had all the functions I needed in spades but I thought about the cost of buying the charts and keeping up to date plus the high res made everything too small for my myopic eyes. I now carry a couple of hand held garmin 76s, one that I use for speed and bearing and another in my pfd in case I go over the side along with a hand held vhf which I would use to call for help and give location. The garmin is okay but I'd like something mounted that I can read from 6ft away.

I'd be interested in hearing opinions on this idea also. My aim as far as navigation is concerned is self sufficiency and simplicity (sight reductions don't count).
thanks

[ntica]

I'm no expert but... I have checked the Furuno gp32 (the chepest) If any it would be this one. I'm also checking satnav/iridium tele. 

[gpdno]

Well if you want to only use a sextant for navigation, the only real point to a gps would be to double check yourself.  In that case you really only need the lon/lat display from the gps.  Personally, I like the idea.  I'm starting a 10 week course on celestial navigation in about two weeks ;)

On my own boat, I have a Garmin 521s and a handheld Garmin 60Csx.  If I were to cross the ocean old school with out the fancy electronics, I just would unplug the 521s.  At that point; a few charts, my compass, sextant, clock, and almanac are all I need.  If I were ever in doubt, I could just power-up the handheld to check my lon/lat and doing that 2-3 times a week, the batteries would last a few months.

At that point, waypoints, tracks, and those other electronic information/data become redundant...

I would keep your handheld and spend the money you save on a real nice sextant and watch ;)

Greg
s/v Family Time
Watkins 27 

[Oldrig]

I would keep your handheld and spend the money you save on a real nice sextant and watch ;) 

You don't even need a good watch, although it would be nice to have one.

Get three el-cheapo quartz digital watches, set them all to GMT and keep them protected in a case, and you'll have a chronometer that's better than most of those beautiful, gimballed, mechanical timepieces.

Good luck!

--Joe

[jpfx]

for a timepiece I found a casio watch which seems to fit the bill and cost me $19 on ebay.
it's a casio AW-80 and comes with dual time zones, data bank, snooze, timer and alarm. the face has some luminosity but it's lit at the press of a button also.

GPS wise, I think I've settled on the furuno GP33, it uses 5 watts when running which isn't much worse than the others.

Whether I get one is still up in the air though, as the comment that a reliable sextant struck a cord. I do have a Davis 25 and I'll probably stick with that until my sight reductions expose errors in the sextant (possibly never).

[CharlieJ]

For just a simple GPS, telling you lat/lon, speed over ground, etc I'm really liking the new Garmin 76 CX I bought- WEST Marine had them on sale for $149  a month or so ago.. Good deal. Oh,  and I didn't get the chart module- just the plain GPS.


Replaces my old Garmin 72 and 76

[marujo_sortudo]

Haven't used the ones you're talking about.  I've been using my Garmin eTrex Vista handheld in a similar fashion, and in think handhelds are fine for this function as I only really use it for checking against the chart.  Of course, the waypoint navigation on it sucks as it only gives me eight compass directions, no option for bearings in degrees.  It does have a great function where you can take the altimeter graph and essentially turn it into a barograph.  If only the waypoint navigation was better, something like that would fit my bill.

[Rick Westlake]

The only thing that money buys you in a GPS is a larger screen and a more-detailed display. The accuracy is inherent in the space system and the control system.

A navigation-grade GPS system will give you a fix that's accurate to less than 10 meters (33 feet), if it's been running for a while. The longer it runs, the better the fix - but, because of the built-in limitations of the "navigation-grade" receiver, it won't give you much better than maybe 15-foot accuracy. That is 15 feet, of latitude and longitude, measured for any point where your receiver might be.

I'm a cartographer. I taught cartography, and an introduction to geodesy - the applied science of the exact size and shape of the Earth, to put it most simply - for the last few years of my career. At 1:40,000 scale, the likely scale of the most-detailed "harbor and approach charts" made by NOAA, 15 feet is represented by five-thousandths of an inch. Half a hundredth of an inch. I used to plot lat/lon positions to that level of accuracy, in the drafting room, on the Mercator projection used for paper nautical charts; and you have no idea how sharp a pencil it takes to plot a point with that level of accuracy!

The cheapest and sleaziest GPS receiver you can buy is more accurate than the best paper charts that the Admiralty, or NGA, or NOAA, have ever produced.

[Captain Smollett]

The only thing that money buys you in a GPS is a larger screen and a more-detailed display.

...

The cheapest and sleaziest GPS receiver you can buy is more accurate than the best paper charts that the Admiralty, or NGA, or NOAA, have ever produced.

Again, excellent stuff here, Rick, and thank-you for posting it.

As I understand what you are saying, my $100 Garmin hand-held is essentially providing the same information as $500 plotting instruments, but with less 'eye candy.'  The inherent accuracy of the data is no better.

That about right?

The only thing I'd add is that the paper charts don't require batteries.   ;D  And, well, do you REALLY need 15 feet accuracy?  I mean, my boat is 30 feet long!

[jpfx]

I question that cheapest is good enough. There's serious considerations to be made based not the least upon an extremely hostile (for electronics if nothing else) environment.

My requirements are/were that it was reliable within that environment.
low power consumption
easy to read from the tiller.
sufficient functions to plot a course and provide visual/visible prompts to keep me informed.

I picked up a si-tex GPS-90 mkII for a good price new. It's 90s technology by anybody's standards but I think it fulfills the role well. Built like a brick shithouse, large visuals, full keypad for simple way point entry, etc. Si-tex (I think) serve commercial users more than consumers and I'm comfortable with that because I expect rightly or wrongly a reliable product as a result.

[Captain Smollett]

I question that cheapest is good enough.

The biggest factor is how one plans to use it.  I think the point was that the most basic lat-lon information is the same for the cheaper units.

If one is choosing to be a "celestial navigator" and rely more on traditional methods as primary navigation, spending money on the bells and whistles of the GPS becomes less desirable.

[CharlieJ]

A point that should also be made, or a reminder anyway.

ALL chartplotters, cheap or expensive, are based on the paper charts current at the time. ALL GPS units, even the cheapest, can tell you exactly where you are but that might not be where the CHART thinks you are. Many charts were originally made years ago using non-GPS methodology. That sometimes  shows places in wrong spots.

A recent example I read was the west coast of Mexico's Baja. Many charts are 1 1/2 mile off and the thought is that when the USS Ranger made the original survey, the chronometer aboard was 1 1/2 minutes off.

Many spots in the Bahamas are off by a bit also. I remember one place where the entrance channel was 1/4 mile off from the charted location.

Bottom line-do what ALL nav devices tell you- use ALL available info, and get your head up and look around- the Mark I eyeball, coupled to a brain (in gear)  is still the most important tool aboard.

[jpfx]

none of the gps I listed are chart plotters, they have no mapping facility. That was the point.
however I don't intend to place my trust on 'the cheapest is good enough' or 'mk1 eyeballs' either.
my eyes are particularly poop anyway and it was never about getting the cheapest gps. I can think of many reasons why a cheap gps will not perform reliably. Sure while it does work it might produce far, far better fixes than I can ever manage but it might also be throwing out the compass, etc, etc.