Whats the differece between marine and auto gps units?

elton said:
Some of the post above are referring to a GPS "puck". This is a device that has no display, and is designed to plug into a laptop loaded with navigation software.
Click to expand...
Yes thats right but it does provide a basic data display on your laptop.Download Seaclear;OpenCPN; and if necessary suitable charts.
In the US you are oh so lucky in that the NOAA provide all the charts of the USA and its territories including inland waters such as Lake Michigan to free download for use in the above.
If you use Open CPN you also get free tidal data.
I have on Seaclear the whole of the Pacific seaboard;Florida;The Bahamas;Puerto Rico;US Virgin Islands
plus everything the US owns in the Pacific.
 
Some car GPS have a function to lock it to the nearest road but otherwise you will often find that if you use a road that is not mapped it will show you over the fields. Similarly if you use a ferry it will show you over water.
 
GPS = Global Position Syetem - the sattelite net that produces the signals to tell you where you are.

Sat Nv shorthand for a machine that enables you to navigate using the GPS signal to tell the machine where you are.

Car Sat Navs use the signal to aid navigation on roads using built in maps

Marine chartplotters use the signals to telate to built in charts - mostly of the ocean but with adjacent "land bits" as well.

Either application will also have programmes for additional features to aid the user. Marine ones are far more complex because they use many more functions such as recording tracks, giving courses, constructing routes, calculating SOC COG and XTE plus many other function that might be useful when navigating over a fluid surface rather than a fixed road.

The GPS signal is "cheap" to acquire - I use £20 dongle. However it is of little use without a method of display or using it - and this is waht costs the mpney and why a versatile "marine" unit made for a limited market is more expensive than a simple car unit made in the millions for people who are incapable of reading a map and road signs.

The simple display units like the basic Garmin have gone out of fashion as people want more sophisticated units, aand increasingly on boats are using PCs as displays or multifunction display units.
 
Gerry said:
Our Garmin 152 gps is on the blink and when surfing for a new one I see an enormous difference in the cost between automotive and marine units.

All I really want to do is display a lat and long..... so would an automotive unit do this, even when crossing oceans?
Click to expand...

The Tom Tom gives just latitude and longitude....Well my model 700 does :)

It will also display a compass
 
Oh dear Tanona! It's becoming very hard work to stay a Luddite :-)
Thank you for your explanation, that makes sense. So they are both GPS based but have different add-ons. If I can find an 'auto' one that will display lat-long in the form I want and even maybe a compass I will have struck gold, back to the surfing then.
 
Gerry said:
So probably an auto unit would do me very well at a far cheaper cost.
Click to expand...

I think you should look at how your proposed auto unit displays lat/long coordinates before deciding. You'll probably find that the figures are very tiny. Entering waypoints and navigating a route will be far more difficult than on your old Garmin 152.

You said the 152 was "on the blink" - what does that mean, and might it be repairable?
 
Tranona said:
The simple display units like the basic Garmin have gone out of fashion as people want more sophisticated units, aand increasingly on boats are using PCs as displays or multifunction display units.
Click to expand...

My old h/h Magellan 320 has a serial nmea o/p which I have used with an old version of Autoroute and with OpenCPN.
I've recently bought a usb gps dongle for OpenCPN and tried it with the old Autoroute but cant get it to work as I can't find where to set the serial port # within Autoroute :mad:
 
If all you want is lat and long, then just buy a handheld GPS - pikc them up ion ebay for next to nothing. Most of them enable you to input waypoints and that will give you things like cross track error, SOG and COG. Sure, most sat nav will display lat and long but the battery life isn't good in comparison with a handheld. I used to use a handheld for navigating on our last boat - made a stand for it so you could read it from the helm. Only downside was the steam driven way to enter waypoints.
 
Gerry said:
Thanks Elton that, I think, is what I was trying to ascertain! So a car satnav would not give me the info that I am looking for at sea ie Lat and long ?

What are the basic differences then between satnav and gps? In my ignorance I thought they were the same thing....
Click to expand...

The receiver is the same and they may well both use the same chipsets. The software in the car units which gives you these nice 3D map displays is sold in vast numbers worldwide so is low cost for the user, where as the software that gives the yotty nice chart like pictures is sold in far lower numbers so tends to cost more, even before the yotty premium is added. Now the low cost PC plotter packages are becoming more common and usable perhaps the cost of dedicated plotters will fall.

As for being usable at sea, my TomTom gives me lat and long so could be used with paper charts at sea. Mind you a cheap handheld would be better as it does do some of the sums for you.
 
Gerry said:
Excellent point awol!

Okay back to the drawing board, swallow the cost or stick with the handhelds......
Click to expand...

I would.


You can get a new 152H for under £200 no problem.

I bet they wont be around for much longer.... only of interest to the likes of you and me, and a few dinosaurs ..... most these days only use plotters and don't know what a chart is
 
If you use a modern car GPS system such as TomTom to navigate to a waypoint, it will try to direct you by road rather than giving you a course to steer. Also, it will probably not show your course over the ground.

I use an old Garmin GPS III+ which works well as sea. This has basic road maps but is unable to work out a route. As a result, it is designed to navigate using a route of waypoints and is more suitable for use on a boat. The maps are quite useful as they provide a basic coastline for reference. It is also easy to connect it to a 12 volt supply.
 
Gerry said:
So they are both GPS based but have different add-ons. If I can find an 'auto' one that will display lat-long in the form I want and even maybe a compass I will have struck gold, back to the surfing then.
Click to expand...
Except that it:

  • Won't have a sunlight readable screen
  • Won't be waterproof
  • Won't display SOG or COG
  • Won't have an anchor drag alarm
  • Won't display nautical miles or knots.
 
elton said:
To the best of my knowlege there's no such thing as an ""auto gps unit". If you mean a "satnav", it's an entirely different thing to a marine gps, such as the Garmin GPS 72/76. Differences are too numerous to mention. Perhaps someone who owns a "satnav" can tell us what the display shows when you're 200 miles away from the nearest road.
Click to expand...

Depends on the satnav...

The Tom Tom 700 can be put to a navigation display and displays lat long.
and satellite status.
 
Well I'm not sure..
Don't need to read it in the sunlight, it's for below decks.
The Garmin 152 isn't waterproof either and has lasted 8 years.
Have a separate log, and also on the handhelds.

As for not buying auto for marine use well although we certainly haven't done it (yet) for navigation we do it all the time for other 'stuff'. I really resent paying a premium for something just 'cos it's labelled Marine!

Useful inputs from all though, thanks very much. Certainly made me think!
 
I have a garmin car gps that I bought for 59 euros, it displays lat and long to an accuracy finer than I can sharpen my pencil to,it shows very accurate speed over ground and direction to a lat long waypoint, I would use it to sail around the world without hesitation as long as I had a sextant to back it up if the gps chip wore out (they all burn out after a few years according to the technical department where I bought my last gps from) or if the Americans swith off the signal at anytime.

The only differences that I can see between a car gps and a sextant is, a sextant is accurate to a mile on a good day and a car gps is accurate to 3 metres all the time.

I have never used electronic charts and never intend to as one electrical storm, power failure or a pereson in America flicking the wrong switch off when he leaves the office at night could mean the loss of boat and crew.
I would never want to sail anywhere without a paper chart covering the area, bearing that in mind, I can not see the problem using a car gps.
 
Zorro said:
[...] a car gps is accurate to 3 metres all the time.
Click to expand...
Which is an illusion generated by a process called 'pinning': the displayed Lat and Long being held until the vehicle moves at a pre-set speed or covers a pre-set distance (when it is updated), thus giving the illusion of a higher level of accuracy than genuinely exists.

The position given by a marine (or other non-automobile) GPS can be seen to 'hunt' around a given position over time - which reveals the true innate inaccuracies of a satellite positioning system.

The reason 'pinning' is used with automobile systems is so that when you're stationary at a set of lights (say), the mapping software will 'believe' you're stationary - otherwise it would 'think' you've started to move ... oh no you haven't ... oh yes you have ... ah, now you've started to go backwards ... etc. Confusion would reign, and listening to a voice reporting that kind of uncertainty would be guaranteed to drive you nuts.
 
You must log in or register to reply here.

Other threads that may be of interest

Y
The Seafarer 700 and NASA clipper sounders saga
Replies
10
Views
436
Dellquay13
Dellquay13

Share this page

Top