Garmin Handheld devices - GPS vs. Electronic Compass

[Stu Jackson]

I'll ask again, what GPS unit? Unless I missed it, if so, apologies. Or maybe I forgot to ask...

[OldFrog75]

Originally Posted by Stu Jackson

I'll ask again, what GPS unit? Unless I missed it, if so, apologies. Or maybe I forgot to ask...

Garmin 76s...

[OldFrog75]

John, thanks again for taking the time to pen you lengthy reply.

Regarding the following:

"But, it seems that you are not as familiar with navigation, GPS or otherwise, as you mentioned earlier (where you wrote: "FWIW, I do know the definitions of course, heading, bearing, track, etc."), as you are assuming that your heading has anything to do with a bearing....it does NOT....

And, I think this misconception is the primary cause of the confusion here!


As everyone has already written, your "heading" is merely where the boat is pointed....and has NO relationship at all to bearing, etc...

Bearing (whether to a "waypoint" or to anything) is based on WHERE you are and WHERE the other thing is....and this has NO relation to your "heading" at all!"

I do know that. Perhaps I misspoke somewhere. Although the bearing to a waypoint does not change regardless of heading, the degrees to the waypoint does change and is important information when trying to optimize tacking angles. The degrees to the waypoint is dependent upon an accurate measure of the heading, whether that be by compass or GPS.

[hamburking]

Here's a pic of the Garmin GPS 60 I used for years on my C&C25.
It had big numbers...easy to see in the cockpit. I had a RAM mount...it would swivel to be viewed in the cockpit, and back in for security, or anchor watch. 12V cord, so it was ON all the time...pulled just about 0 amps. Also would run 18 hours off 2 AA batteries, if needed. It was a great setup. I also carried a plastimo handheld compass, but never needed it.

[ka4wja]

OldFrog,
I think there may be some more confusion here, due to terminology???

When you say "degrees to the waypoint", to me that is the bearing to a waypoint.....such as "120*M"....

But, perhaps what info you want is "how many degrees off the bow" is the waypoint???
If that's the info you need, then that's a simple thing to know...it's your heading +/- your bearing to waypoint....
So, knowing your heading in that case would be a necessity....

But, regardless of what you call the info you need ("degrees to the waypoint", etc.), it matters not....
The answer to your original question remains the same: use the compass!!
(actually the best answer is: install a compass!!!)

Originally Posted by OldFrog75

I do know that. Perhaps I misspoke somewhere. Although the bearing to a waypoint does not change regardless of heading, the degrees to the waypoint does change and is important information when trying to optimize tacking angles. The degrees to the waypoint is dependent upon an accurate measure of the heading, whether that be by compass or GPS.

As I'm sure you gleaned from my postings, I'm not a racer....although I HAVE raced and HAVE been a navigator in a race, I'm not a racer....and as such, I'm not privy to what info you all might need....(back when I was racing, is when we needed to do trig problems to calculate VMG!!)


Fair winds..

John

[Stu Jackson]

Originally Posted by OldFrog75

Perhaps I misspoke somewhere. Although the bearing to a waypoint does not change regardless of heading, the degrees to the waypoint does change and is important information when trying to optimize tacking angles. The degrees to the waypoint is dependent upon an accurate measure of the heading, whether that be by compass or GPS.

True, the bearing to a waypoint does not change regardless of heading...when you're not moving.

When moving, unless pointed directly at the waypoint, the bearing to that waypoint WILL change. And so will the degrees to it, which, simply, is the direction to that waypoint from where you are.

That's why many have pointed out that the VMG feature of the GPS is very important and is used for sailing upwind (and down) for determining tacking angles. When it hits 0 then tack, assuming you're close to the waypoint on a club race and have figured out all the rest of the stuff.

The degrees to the waypoint is dependent upon an accurate measure of the heading, whether that be by compass or GPS.

This is what I said before was "irksome" about GPS and the unfortunately and often misused word: heading.

The way you've used them in that sentence, THEY ARE TWO DIFFERENT THINGS.

Heading: Version 1 - the way your bow is pointing, i.e., compass reading

Heading: Version 2 - the GPS's use of the word heading which is the COG the GPS is measuring based on HISTORICAL data of where you've been.

These are two wildly different things.

The degrees to a waypoint, as far as your GPS is concerned, has absolutely NOTHING to do with your boat's heading (Version 1), it can, and has to be, Version 2.

I'm going to look up my Garmin GPSMap 76Cx manual and see if there is any discussion about this "feature." I don't recall it at all. Maybe I'll check out yours, too.

Still makes no sense to me.

[OldFrog75]

Originally Posted by ka4wja

OldFrog,
I think there may be some more confusion here, due to terminology???

When you say "degrees to the waypoint", to me that is the bearing to a waypoint.....such as "120*M"....

But, perhaps what info you want is "how many degrees off the bow" is the waypoint???
If that's the info you need, then that's a simple thing to know...it's your heading +/- your bearing to waypoint....
So, knowing your heading in that case would be a necessity....

But, regardless of what you call the info you need ("degrees to the waypoint", etc.), it matters not....
The answer to your original question remains the same: use the compass!!
(actually the best answer is: install a compass!!!)

As I'm sure you gleaned from my postings, I'm not a racer....although I HAVE raced and HAVE been a navigator in a race, I'm not a racer....and as such, I'm not privy to what info you all might need....(back when I was racing, is when we needed to do trig problems to calculate VMG!!)


Fair winds..

John

Thanks again and you're right. Terminology can be confusing. This particular measurement on my model is called "turn", as in how many degrees to the right or left do you have to turn to get to the waypoint.

I know it's a simple calculation but fortunately the unit does the arithmetic and updates and displays the answer in real time.

The unit probably has 60 different functions that can be accessed/utilized - I only use about 8.

[Stu Jackson]

Originally Posted by OldFrog75

Garmin 76s...

Garmin, those bastards, are now charging for old manuals, so I can't read it. Sorry.

Still sounds unreal to me, but you have the manual and I don't!

[Stu Jackson]

OK, I found one online.

Pge 20 says:

It is important to note that while using the GPS receiver for navigation, the Compass Ring does not
When the Electronic Compass is "ON", the compass
act as a true compass. You must be moving for the Compass Ring and Pointer to
icon will be displayed on the Map, Compass, and update and correctly point towards your destination. When using the Electronic Compass for navigation, the unit must be held level or the compass reading may
be inaccurate. If the unit is not being held level, a message "Hold Level" will be
displayed.

Seems simple to me, now. You have a unit that can be used just like a magnetic Boy Scout compass IF YOU HOLD IT LEVEL.

ITWMB, I'd disable the compass feature and use only the GPS for the information you're looking for to navigate.

[OldFrog75]

Originally Posted by Stu Jackson

OK, I found one online.

Pge 20 says:

It is important to note that while using the GPS receiver for navigation, the Compass Ring does not
When the Electronic Compass is "ON", the compass
act as a true compass. You must be moving for the Compass Ring and Pointer to
icon will be displayed on the Map, Compass, and update and correctly point towards your destination. When using the Electronic Compass for navigation, the unit must be held level or the compass reading may
be inaccurate. If the unit is not being held level, a message "Hold Level" will be
displayed.

Seems simple to me, now. You have a unit that can be used just like a magnetic Boy Scout compass IF YOU HOLD IT LEVEL.

ITWMB, I'd disable the compass feature and use only the GPS for the information you're looking for to navigate.

Thanks Stu. I also read the manual before I called Garmin. There is not a detailed summary about the difference between the Electronic Compass and GPS, the advantages/disadvantages of each, or how to optimize the on/off Compass vs. GPS -

...hence my question.

Obviously I'm one of those people who need things spelled out and would like the manual to say something along the lines of, "if you want to do this, use that. If you want to do that, use this. If your activity is X then set the unit to Y. If you do this you optimize or limit yourself because..."

Same thing with my question about the Track Log setup. Which setting provides better results, "Auto" or "Time" and additionally what parameters within each of those produce the best results. What does "Most frequent, Normal, or Least frequent" mean and how does it affect the data when exporting to a mapping service like Google Earth? Do I need a data point every 2 minutes to see if I'm steering a straight course of should it be set to every 5 seconds? I don't know the answer.

[Stu Jackson]

Originally Posted by OldFrog75

Thanks Stu. I also read the manual before I called Garmin. There is not a detailed summary about the difference between the Electronic Compass and GPS, the advantages/disadvantages of each, or how to optimize the on/off Compass vs. GPS -

...hence my question.

Obviously I'm one of those people who need things spelled out and would like the manual to say something along the lines of, "if you want to do this, use that. If you want to do that, use this. If your activity is X then set the unit to Y. If you do this you optimize or limit yourself because..."

Same thing with my question about the Track Log setup. Which setting provides better results, "Auto" or "Time" and additionally what parameters within each of those produce the best results. What does "Most frequent, Normal, or Least frequent" mean and how does it affect the data when exporting to a mapping service like Google Earth? Do I need a data point every 2 minutes to see if I'm steering a straight course of should it be set to every 5 seconds? I don't know the answer.

I understand. Manuals are written by people who never use the products...drats.

You, sir, are asking for entirely too much. :smile :

Tracks? This one is simple. It basically doesn't matter. Start out with the one that uses the most memory, i.e., most points on the track. Then see how much memory it uses up based on what size memory stick or device you have in your unit, based on your average sailing times. I've gone for over a week this way and still only used up less than 20% of the memory.

If you space them out, for a short run you'll get useless dots if you download the data to MapSource and then look at it on your computer at any zoom scale.

Try this: walk around your neighborhood with the GPS on different track mode, and try them out. That's what I did when I got my unit.

Sometimes asking for the final result before you use the unit's options is asking for too much too soon.

Only YOU know how you use the unit, that's one reason why manuals are sometimes generic.

[smac999]

I only use my garmin handheld for hiking so it might be a bit different.


mine is always in compass mode. as I'm always moving pretty slow. 2-3m/h.


on mine you can change between compass and COG by holding one of the buttons down. maybe there is a speed setting. I haven't played with the settings in years. just use it as is.


I doubt the battery difference is much between using compass or COG. mine last 15-20 hours. just bring more AA batteries...


my compass needs to be calibrated each time the unit is turned on and used. otherwise it's way off. compass calibration is in the menu. I use it for aprox heading so if I'm heading to w/p the arrow points in the correct way. I certinly wouldn't use it as a compass for nav. it would be impossible to even hold it facing the exact correct way.

[hamburking]

Originally Posted by smac999

I only use my garmin handheld for hiking so it might be a bit different.


mine is always in compass mode. as I'm always moving pretty slow. 2-3m/h.


on mine you can change between compass and COG by holding one of the buttons down. maybe there is a speed setting. I haven't played with the settings in years. just use it as is.


I doubt the battery difference is much between using compass or COG. mine last 15-20 hours. just bring more AA batteries...


my compass needs to be calibrated each time the unit is turned on and used. otherwise it's way off. compass calibration is in the menu. I use it for aprox heading so if I'm heading to w/p the arrow points in the correct way. I certinly wouldn't use it as a compass for nav. it would be impossible to even hold it facing the exact correct way.

Please accept my apology for totally disagreeing with you. I do concede that a compass is an invaluable device. But a handheld gps takes you to the next level...using the data of your past location, current location, and desired destination to give you the processed information you want/need, without need to constantly refer to a chart to lay off bearings, take fixes, or do the math by manually.

It boots in seconds, and has a fix in less than a minute. After initial setup when new, requires no recalibration ever, unless moved hundreds of miles while off.

Attached are a few pics of my inexpensive gps 60 aboard my sailboat. I bought it on ebay for $40 (including shipping). In these, I am out of sight of land, only water to the horizon, and yet it gives me all the info I need to proceed directly to my destination. I am a huge fan of this technology. If you used only a compass (or the gps as a compass) you would be limited to dead reckoning, and you'd better have your chart and pencil handy at all time.

I grew up using classic navigation techniques...fixes, bearings, transits, azimuths, etc. It took a huge amount of effort and time to accurately plot your position and course that way. I suffered with LORAN (both A and C). Early "satnav" was ridiculously expensive. When the garmin45 was introduced, it was the first truly practical handheld gps at a reasonable price. It revolutionized navigation. Its remains the largest (by volume) selling gps device in history.

The integration of the map into the gps, in the form of chartplotter has once again changed everything. But you can't get a chartplotter for $99 at walmart...thats why the handheld gps is such a big deal...its for everyone.

If you just use your gps as an electronic compass, you are not using any of its capabilities. Its time to press MENU and start learning your device.

[smac999]

I use my GPS as a GPS. my post says I would never use it as a compass. if I actually ever had to follow a bearing the GPS would go away and the compass would come out. and the COG / electronic compass debate becomes irrelevant.


or on a mapping gps you make a waypoint at far distance at that heading, and make a route that draws a line to follow. but that line is drawn using the map data not the direction of the internal compass.

[charliehows]

?? I've got 2 handhelds, they both give pretty accurate bearings once left sitting in the cockpit for a few seconds, as well as lat/long, sog, eta, etc, etc ( about 100 other useful functions). Couple of people stating categorically that they dont work as a compass - have you ever actually used one these things?