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Garmin 3-axis Compass Hints and Tips

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KeyResults    604

GPSr compass hints

I guess there are some of you, our geocaching brothers and sisters, who are less than satisfied with your GPSr compass performance. Of particular interest are the ultra modern tri-axial, or 3-axis, electronic compasses in the latest GPSr units. These units have some pretty slick capabilities but there are some strict rules to using them so they provide accurate results. After having some frustration with mine for a short time (Garmin 62s), I finally got it whipped into shape and performing well for me AND I have learned to recognize when it needs some TLC by misbehaving on me from time to time. An example is when my BFF and I, using the exact same units, are given very different paths to the cache from the trail we are standing on. She goes one way and I go the other. One of us needs to recalibrate our compass! And we both know who as soon as we sign the log and replace the cache ;)

 

First, here are some facts that you may or may not know about your 3-axis digital compass:

 

1)      The most current versions are delicate instruments, comprised of highly sensitive magnetometers and accelerometers. They can get knocked out and will not function, like ever.

 

2)      They are able to detect and calibrate to a wide range of magnetic fields from barely perceptible Milligauss to very strong magnetic fields. However, they are easily knocked out of calibration by something as simple as being on the cradle of your vibrating handle-bars, or changing the batteries.

 

3)      There are only a handful of makers of the specialized integrated chipsets in existence and they supply virtually all manufacturers of avionics, navigation, and smart phones.

 

4)      Combined with a specialized GPS (and now GPS/GLONASS) integrated chip set – also from only a handful of sources – they comprise the modern GPSr. Add communications and you have the modern smartphone!

 

5)      The compass should be able to consistently provide 1-2 degrees of accuracy, repeatedly. If after performing proper calibration, and checking a few other things below, you are unable to get this accuracy, your unit may need to be replaced.

 

6)      When I say these little guys are sensitive, I mean REALLY sensitive. If anyone is interested in the tech behind these little jewels, let me know and I’ll fire you some excellent bedtime reading.

 

Okay, with that out of the way:

First, CALIBRATE YOUR COMPASS EVERY TIME YOU CHANGE BATTERIES! Seriously. Yes you! You know you don’t… ;) As it turns out, the better the unit, the more sensitive these little buggers are. Even changing the batteries effects the currently stored calibration. Seriously. Did you know that even the types of batteries used makes a big difference? It does, absolutely. According to the compass manufacturers, Lithium batteries have the least magnetic impact, followed by Alkaline, then rechargeable types like NiMH or NiCad, with the latter having the most impact on the compass. Even changing the brand, or capacity of rechargeable batteries used affects the compass calibration.

 

Now you know why there is a menu setting to tell the unit what type of batteries you are using! It is so the Compass can be aware of the differences in battery magnetic field. While you’re at it, is your battery type setting correct? ;)

 

When you calibrate, you must complete ALL three axis: pitch, roll, and circle, in the order instructed by your device maker. If any of the three calibration steps (axis) aren’t completed properly you must repeat until you get it right. It’s all three or none!

 

Sometimes, there are just weird places that will set your compass off big time. It’s rare. In those cases, if you can field calibrate successfully, then go for it. The units are able to discern significant ranges of magnetic force and filter accordingly, but only if successfully calibrated.

 

Don’t attempt to calibrate your compass in your car, sitting on your car, or anywhere near your car or any other significant metallic objects. Be aware of anything electrical nearby too. Power lines obviously are a no no too. The US Military has compass calibration guidelines for minimum distances from darn near everything including Tanks, and Machine Guns…true statement.

 

Take note that keeping your highly sensitive magnetometer in close proximity to your tablet, smartphone, magnetic pen and lanyard, rfid badges, etc., is, well… never mind. ;)

 

It should be noted that your unit allows for you to set the compass to true north or to auto correct (declination, or variation) for magnetic north. I like to mimic a needle, so I tend to use magnetic north.

Also be careful that your unit isn’t set to “lock on roads” rather than supporting “direct route” which is what you want for geocache hunting “as the crow flies”

 

Finally, be very aware of what profile you are using. General or Recreational profiles aren’t very well suited to geocaching and can definitely mess with your compass behavior on Garmin units especially. Be sure you are using a “Geocaching” profile. Also, note that there are different “dashboard” options too while in each of the screens, including the compass screen. Experiment with the geocaching dashboard or the geocaching details dashboard while on the compass page of your geocaching profile. Also, the compass behavior is different when you have locked in on a geocache vs not.

 

I hate that so many think that their compass sucks. I hope something here helps you to sort that out like it has for me and most of my caching buddies.

 

A few other hints before I go:

Update your firmware! Figure out how to do that or get someone to do it for you! It’s important.

 

Consider taking your unit to an event and comparing it’s configuration with others. Compare performance too while you’re at it.

 

Sometimes a good old hard reset is called for. Don’t be bashful…you do have a back up right?

 

TEST YOUR COMPASS
You can test that your 3-axis compass is functioning properly, and accurately, by creating a wooden platform, leveling it perfectly, then marking magnetic north precisely as you can on adjacent non-magnetic vertical post or wall using a regular compass needle. Put the needle away, then after calibrating your unit, set it for magnetic north and place it on the table face up in compass mode. Align North with the needle and with the mark on the wall or post. You should be pointing to magnetic north. Now rotate the unit clockwise on the table and the needle should remain within 1-2degrees of the magnetic mark. It may waver slightly while you rotate, but the pointer should definitely and quickly return to the north mark within 1-2 degrees. Now rotate the unit CCW on the table, same thing, your needle should still be locked on that magnetic mark you made using the needle. If you cannot achieve this 1-2 deg accuracy, there is definitely something wrong. If the needle sticks more than 1-2 degrees away from north mark, something is wrong. If after you’ve exhausted all the things listed here, you should seek out advice from the manufacturer.

 

Good luck!

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Dhaulaghiri    269

Wow, Kenny, just wow!

I've never paid too much attention to the compass function of my GPSr-units and most of the time they'll get me close enough to GZ to make the find. However, I now realize the performance could be even better and I'm definitely going to tinker around for a bit to see what's what.

Upon reading how sensitive these devices are my first thought was 'oh, so I practically have to strip naked to avoid influencing issues with the compass?!?' and then realized at least on of us was gonna have an easy time with that.... an image of Bert in his famous man-kini sprang to mind and I had to go grab a beer to get that image out of my mind again ;)

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KeyResults    604

A small compass in the top of a hiking stick never need calibration or batteries.

Sadly, too few people know how to use one of those properly either. I know this from teaching orienteering skills to Scouts for several years.

BTW: While batteries aren't needed, you still must calibrate your needle to your location to account for declination if you want real accuracy. ;)

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KeyResults    604

Oh, and the compass test works for any compass. Compasses should never stick or vary more than 1-2 degs. If they do they should be replaced.

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SockPuppet    192

I picked up a compass in a cache that pointed South instead of North. I think I ended yup giving it to Snoogans. No that I wanted him to get lost or something :D.

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Mr Muddy Buddy    223

I can say that in my many years of having a 60csx and now a 62s, I have never used the compass.  

I have always set it to bearing, which shows the direction to the waypoint.

On the rare occasion that a multi-cache wants you to walk in a certain compass direction, I can usually estimate this from the bearing, and get to point B from point A.

I am still not clear what advantage a compass gives you out in the field.

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KeyResults    604

Good point Stan, I've heard some others say similar. Here's the rub: you may not realize it, but you're using your compass, even if you never go to your compass screen. Er, well your unit's internal "brain" is.

 

The compass, at the most basic level, is tasked with determining which cardinal direction you're facing while standing still, among other things. It plays a  role more often than we realize, especially when gps lock is sketchy in heavy canopy. Stable headings are potentially less bouncy and more confident with a solid compass "assist" in the mix. This is especially true with modern compensated 3-axis units. 

 

No matter what, your unit will behave best if you keep your GPSr's internal compass calibrated.

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cachestacker    736

I can say that in my many years of having a 60csx and now a 62s, I have never used the compass.  

I have always set it to bearing, which shows the direction to the waypoint.

 

 

Isn't the arrow that says "go this way" the same thing as the compass, essentially?  It's using it.  And if it's off, so is the arrow.

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HoustonControl    1,046

I rarely had the electronic compass turned on on my 60, because it was two-axis only and you had to hold the unit level... it was a PITA.  So, basically, you had to be moving for the arrow to work correctly.  On the 62s, I usually leave it turned on -- the advantage then being that the arrow points to the desired waypoint, even when standing still.  I usually don't recalibrate it after changing batteries (but I have noticed the accuracy suffers a lot of the time right after changing them), and have had problems with trying to calibrate the compass while sitting in the car.  Kenny's article ironed out a lot of those issues for me.  Thanks, Kenny!

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KeyResults    604

It's a system:

GPS= location, elevation, and distance

Compass (magnetometers x 3) = direction

Accelerometers = gravity / relative motion

Barometer = altitude

It's a control processor, know how and software that put all the above to good use in a solution package (GPSr or smartphone + app) and our enjoyment. It's all complicated and flawed. Some more flawed than others, but getting better.

On another note:

GPS is USA satellite navigation network. GLONASS is essentially the Russian equivalent. Other networks are being deployed even as I write this. If your device has a dual receiver it just means that you have many more "birds in the sky" that may be detected by your unit as an aid in position accuracy. More positioning data points, in this case, is always a good thing. How much better? That's relative to where you are, but it's definitely better. Especially in northern latitude urban settings with lots of obstructions.

Edited by KeyResults

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Mr Muddy Buddy    223

 

I can say that in my many years of having a 60csx and now a 62s, I have never used the compass.  

I have always set it to bearing, which shows the direction to the waypoint.

 

 

Isn't the arrow that says "go this way" the same thing as the compass, essentially?  It's using it.  And if it's off, so is the arrow.

 

 

With the bearing setting (instead of compass), the arrows shows the relative direction between you and the target.

I generally don't care if it's exactly 225 degrees or just a general SouthEast heading.

If I need an exact compass direction, and the distance to travel is greater than 100', then I use a projection.

I guess that all that boy scout training I had as a kid is finally getting put to good use.  

I try to use nature to estimate my directions... you know  which side of the tree the moss grows, the stick and shadow method, the position of the sun and/or moon, the north star, Orion's belt,  which way the barrel cactus leans, which side of a hill do the evergreen grow..... the list goes on.   :coolsmiley:  

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cachestacker    736

But my point was -- without the compass, whether it's on the screen or not, the needle does not work.

 

I'm referring less to the degree compass on the screen than the fact that I get out of the car with someone and we both head different directions based on the arrow (which is using the compass).  Obviously someone's is out of whack....

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Mr Muddy Buddy    223

But my point was -- without the compass, whether it's on the screen or not, the needle does not work.

 

I'm referring less to the degree compass on the screen than the fact that I get out of the car with someone and we both head different directions based on the arrow (which is using the compass).  Obviously someone's is out of whack....

 

I tend to not agree with the first statement.  The needle on my GPSr is pointing to the cache.  

The only time that I calibrated my compass was when I first booted the GPSr right out of the box, 3 or 4 years ago.

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cachestacker    736

 

But my point was -- without the compass, whether it's on the screen or not, the needle does not work.

 

I'm referring less to the degree compass on the screen than the fact that I get out of the car with someone and we both head different directions based on the arrow (which is using the compass).  Obviously someone's is out of whack....

 

I tend to not agree with the first statement.  The needle on my GPSr is pointing to the cache.  

The only time that I calibrated my compass was when I first booted the GPSr right out of the box, 3 or 4 years ago.

 

 

Exactly.  I've done my Oregon only a few times, and more out of curiosity and not because I needed to do so.  Thus my concern with the 62s.  The ones I've seen and played with arrows have seemed highly inaccurate at times.  And that was giving me pause on the 64s.

 

But with KRs tips and tricks, we'll get to see if we can 'fix' some of those and revisit that issue.  Of course, I don't like the idea of having to do that all the time, either.  Like you, I've only recalibrated my compass on the Oregon a few times.  I can't say I'd have ever even thought of doing it every time I change the batteries...

Edited by cachestacker

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Dhaulaghiri    269

Well, I recently bought a 62st and I'm pretty pleased with the accuracy of the compass, that said, with Kenny's comprehensive guide I WILL start calibrating my compass more often!

Edited by Dhaulaghiri

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KeyResults    604

CALIBRATION:

Look, compass calibration is easy and takes less than a minute, 30 seconds once it's a habit. With a few weird exceptions - like highly iron rich, or very electrical areas - the more you calibrate the easier and faster it becomes. I promise you that your GPSr or Phone App will behave much more steady and responsively. Especially if you are a traveler and power up in entirely different places...guaranteed...or your money back ;) 

 

CAN I USE MY GPS W/O CALIBRATING?

So, can you use your GPSr without calibrating your compass? Obviously you can, but you are clipping out a key data point from your GPSr's available sensors, however. In this situation, the best case result is that your accuracy depends on movement for it to calculate COG based on your smoothed position trend and your waypoint fix to be rendered for display. If, however, the compass is whacked out, it's erroneous information will create conflict within the system as the system tries to reconcile bogus information. This manifests itself in bouncing, or jumpiness, as the display tries to smooth the difference between what direction the compass is reporting, and the BRG & COG the GPS is reporting. This is where each vendors' proprietary software distinctions take over and weight all the inputs to try and make sense of it all. 

 

CAN I JUST TURN OFF THE COMPASS?

It's worth noting that I am unaware of any way to "turn off" your compass in a Garmin 62s or 64s GPSr ( though for the life of me I cannot fathom why one would choose to do that!). Since you are unable to disable the internal compass, and you just always ignore the fact that it's wrong, it may be that the unit's internal software will effectively ignore it at some point. That is mere conjecture on my part. That's among the many discussions that I'd LOVE to have with the actual developers of the firmware sometime. Stan's illustrious success, despite not giving his digital compass any apparent attention says you can still git er done.

 

TOO MUCH? SORRY.

I certainly didn't intend to get anybody riled up here or question anyone's empirical methods. Nor did I intend to do a dissertation on digital compasses. My intent was to shed some light on the topic to help some folks who may not understand their choices. I promise I'm not makin this stuff up! As always, YMMV.

 

I sincerely hope you find em all, however you choose to get it done! 

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Dhaulaghiri    269

CALIBRATION:

Look, compass calibration is easy and takes less than a minute, 30 seconds once it's a habit. With a few weird exceptions - like highly iron rich, or very electrical areas - the more you calibrate the easier and faster it becomes. I promise you that your GPSr or Phone App will behave much more steady and responsively. Especially if you are a traveler and power up in entirely different places...guaranteed...or your money back ;) 

 

CAN I USE MY GPS W/O CALIBRATING?

So, can you use your GPSr without calibrating your compass? Obviously you can, but you are clipping out a key data point from your GPSr's available sensors, however. In this situation, the best case result is that your accuracy depends on movement for it to calculate COG based on your smoothed position trend and your waypoint fix to be rendered for display. If, however, the compass is whacked out, it's erroneous information will create conflict within the system as the system tries to reconcile bogus information. This manifests itself in bouncing, or jumpiness, as the display tries to smooth the difference between what direction the compass is reporting, and the BRG & COG the GPS is reporting. This is where each vendors' proprietary software distinctions take over and weight all the inputs to try and make sense of it all. 

 

CAN I JUST TURN OFF THE COMPASS?

It's worth noting that I am unaware of any way to "turn off" your compass in a Garmin 62s or 64s GPSr ( though for the life of me I cannot fathom why one would choose to do that!). Since you are unable to disable the internal compass, and you just always ignore the fact that it's wrong, it may be that the unit's internal software will effectively ignore it at some point. That is mere conjecture on my part. That's among the many discussions that I'd LOVE to have with the actual developers of the firmware sometime. Stan's illustrious success, despite not giving his digital compass any apparent attention says you can still git er done.

 

TOO MUCH? SORRY.

I certainly didn't intend to get anybody riled up here or question anyone's empirical methods. Nor did I intend to do a dissertation on digital compasses. My intent was to shed some light on the topic to help some folks who may not understand their choices. I promise I'm not makin this stuff up! As always, YMMV.

 

I sincerely hope you find em all, however you choose to get it done!

As of the start of this post you've officially become my hero, Kenny! One question; HOW do you know all this / where do you get this information.... I mean this is some serious technical stuff!!!

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KeyResults    604

Thanks Hans. Actually, as with most of us, a career stop! Pretty boring stuff. In this case it was development of embedded systems machine vision technology for some military and transportation focused applications that depended fairly heavily on "location awareness" among other things.

 

But seriously, much of the Garmin specific stuff was just dealing with frustration by studying the technology they used inside their units published by the manufacturers of the chip sets.

Edited by KeyResults

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Mr Muddy Buddy    223

 

CAN I JUST TURN OFF THE COMPASS?

 

 

 

Yes you can.  

From the Compass screen, press MENU, then select the Setup Heading.

Here you have the option of turning the compass to the OFF setting.

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KeyResults    604

 

 

CAN I JUST TURN OFF THE COMPASS?

 

 

 

Yes you can.  

From the Compass screen, press MENU, then select the Setup Heading.

Here you have the option of turning the compass to the OFF setting.

 

I Well there you have it. I just verified the 64 series works the same. 

 

It'll be fun to experiment, head to head, this weekend with compass on and compass off ;)

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davarle    63

Thanks Hans. Actually, as with most of us, a career stop! Pretty boring stuff. In this case it was development of embedded systems machine vision technology for some military and transportation focused applications that depended fairly heavily on "location awareness" among other things.

 

But seriously, much of the Garmin specific stuff was just dealing with frustration by studying the technology they used inside their units published by the manufacturers of the chip sets.

If I had a nickel for every time I developed embedded systems machine vision technology for some military and transportation focused applications that depended fairly heavily on "location awareness" among other things......

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