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electronic compass


scottskaggs
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I'm new to geocaching and already hooked. I got a Magellan 200 for Father's Day and already want to upgrade, scary. I'm looking at the etrex Legend Vs. Vista and I'm wondering if the electonic compass is worth it. I'm also considering waiting on the HCx to come out any suggestions?

Scott

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They are handy when you want to see the direction to the cache (more or less) while you are standing still. They create some issues that make them a PITA at other times to where I turn them off unless I specificly want it on. Garmin does let you toggle the compass by pressing and holding a button.

 

Still a lot of people like having an electronic compass and they sure don't hurt since even people like me can turn them off.

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I a one of those that think they are a huge waste on money. I have several real compasses. Wen I use a compass that is what I use. I own one GPS with a (Magnetic compass) All GPS'r have a compass screen and all are electronic, not all have a magnetic compass. I keep the Magneitic compass turn off in my gps that has one I find it to be a PITA

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What is the downside to an electronic compass (i.e. what makes it a PITA)?

 

I'm in a similar situation as the OP, and ever since my first GPS I've wanted an electronic compass, but now I'm second guessing myself.

They can act erratically sometimes but like RK said you can toggle them on and off. I have a Legend and a 60CS. When I used the Legend I had to walk a straight line for 10-15 to get the arrow to point at the cache. This can be a pain so I do like using my 60CS better.
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What is the downside to an electronic compass (i.e. what makes it a PITA)?

 

I'm in a similar situation as the OP, and ever since my first GPS I've wanted an electronic compass, but now I'm second guessing myself.

I've never had a problem with it. The compass is the RING on the navigation page, it is NOT the POINTER. When people complain about the "compass", they usually mean the pointer, not the actual compass ring.

 

The pointer can appear to be acting erratically, but it's not. It's just doing exactly what it's supposed to do: determining your position, the target position, and then aligning the arrow to point towards it. But once you get close to the cache, and enter the "error zone", the arrow can start appearing to behave erratically. Because of the normal GPS error, the unit may calculate your location as being west of the cache at one moment, and east of the cache a few seconds later. The pointer is just show the results of those errors. If you used a hand-held magnetic compass, it would show the same wacky behavior. But the difference is that if you had a hand-held magnetic compass, you would have already dropped it in your pocket by now. But since the pointer is right there on your GPS, you continue to let it lead you long after you should have put the GPS away and started searching for the cache.

 

Another reason people can think their pointer is behaving oddly is when they accidentally set it to Course Pointer, instead of Bearing Pointer. The Course Pointer tries to keep you on an imaginary line between your starting point and ending point.

 

Of course, there are a tiny percentage of unit that actually do malfunction. But in the vast majority of cases, it's just a matter of people not understanding what's going on in their units.

Edited by Prime Suspect
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The biggest problem with the internal compass is that it is a total battery hog! All the other "problems" with internal compasses (like having to calibrate, and having to hold them level and such) pale in comparison to the fact that, if left turned on, they cut your battery life in half! So...Why not just use a magnetic compass that doesn't require a battery at all and never needs calibration? Use the money towards software or something useful. JMHO

Edited by Alphawolf
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The biggest problem with the internal compass is that it is a total battery hog! All the other "problems" with internal compasses (like having to calibrate, and having to hold them level and such) pale in comparison to the fact that, if left turned on, they cut your battery life in half! So...Why not just use a magnetic compass that doesn't require a battery at all and never needs calibration? Use the money towards software or something useful. JMHO

I fix that be not leaving it on. I toggle it on (single button press) when I need it, then toggle it off. Much faster than taking a compass out of my pocket and lining it up with the bearing displayed on the GPS.

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I'm new to geocaching and already hooked. I got a Magellan 200 for Father's Day and already want to upgrade, scary. I'm looking at the etrex Legend Vs. Vista and I'm wondering if the electonic compass is worth it. I'm also considering waiting on the HCx to come out any suggestions?

Scott

I have one in my iFinder and would never buy another gps without the electronic compass.

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I've never had a problem with it. The compass is the RING on the navigation page, it is NOT the POINTER. When people complain about the "compass", they usually mean the pointer, not the actual compass ring.

It took me a while to figure out what you meant and I kind of agree. The ring and the pointer are locked together because the relationship is fixed by the calculated bearing. There are two possible problems with the pointer, then. The bearing calculation is off or the compass is off. The bearing is off because the GPS puts you at the wrong location. It could put you on the nearest road, for instance. The compass could be off because of calibration or because you are in a distorted magnetic field. You are in or near a steel car or near a metal bridge, steel belt buckle etc. Even given those limitations, I like my 60csx electronic compass a lot and will never be without an electronic compass.
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I used to think that electronic compass was a waste of money. Then I was in Florida in a swamp (geocaching, of course) and did not have a GPS signal. After what seemed like an hour of bushwhacking around in circles I knew that every other GPSr I would buy after that would have an electronic compass.

 

The electronic compass is an optional feature. And like any optional feature, its worthless if you don't know how to use it. On the 60CSx it can be set to come on at particular speeds (I think I have mine on the default). You see a message on the screen when it is on (the message is "hold level"). When the emulated compass (using the satellites) and the magnetic one don't coincide then you see some bounce with the arrow; It is very easy to then calibrate the compass and all is good again.

 

"Total battery hog" is a big exaggeration. I can go an entire day geocaching with 2100mAh rechargables and I never turn my compass off. I do know what a "total battery hog" is because I also have a Garmin IQue.

 

When I bought my latest unit (on line) the price difference was $35. At that price it is definitely worth having even if just to be able to turn it on in emergencies.

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When looking for a cache it's very handy. I let the GPS lie down, magnetic compass on, while I rover the area, looking for the cache. Now and then I go back and check direction and distance to the cache. As the GPS settles in, accuracy often improves, but that's of no value, if you have to run around with the GPS to get the bearings. Without the magnetic thing, you have to resort to coordinate matching instead.

 

Besides, with the magnetic compass (on a Garmin), you also get the air pressure sensor, together (more important) with all the software stuff for elevation profiling and such.

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I'm new to geocaching and already hooked. I got a Magellan 200 for Father's Day and already want to upgrade, scary. I'm looking at the etrex Legend Vs. Vista and I'm wondering if the electonic compass is worth it. I'm also considering waiting on the HCx to come out any suggestions?

Scott

I have only one gps, a 60csx and use the compass all the time. Batteries last all day.

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I too agree, if you don't like it it's easy to turn off.

Mine never gets turned off, with Rayovac hybrids, the 60CSx will last a day and a half. (Longer than me)

Also, I ususally hop in Geomobile, plug it in, turn it on, go to first of day, unplug, look for an hour (Two, more?) plug back in and off to next. Like this it's good for a few days of steady Geocaching. So battery life is not an issue with me. I have 8 Hybrids, I carry spare alkalines, and I also carry Alk's as swag. Drop two in a mini-bag thats marked w/ name and date of batts and you will get an Email saying thanks!

Also, I also have a Vista that I really like, until I get under heavy tree cover. The HCx should do better.

JM.02W

PigPen4X4

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There are several problems with the built-in electronic compasses and the built-in barometric altimeters. The first one mentioned by several already is that they are battery hogs. A couple people suggested turning them on only for a brief period when you actually want to use them. Problem with that in Garmin's case is that the barometric altimeter is always on - you cannot shut it off in the 60CSx, 60CS, 76CSx, 76CS, the new Vista, etc. In the case of the compass, the drain on the battery is astoundingly huge. I find that turning it on even for a few minutes puts a huge dent in battery life.

 

Second point on compasses is that even an inexpensive baseplate compass is easier to use and more precise than the built-in compasses (Suunto, Brunton, and JWA's Silva all have basic baseplate compasses for about $10). They never run out of battery and take only a few seconds to set the direction arrow (setting the equivalent on an electronic compass takes 20-30 seconds). And yes, I have a 60CSx, a Brunton electronic compass, and a variety of orienteering and survey compasses, so I have a good basis of comparison. If you carry the baseplate compass around your neck on the supplied lanyard, it is always ready to hand, without even switching screens on the GPSR.

 

Another point on compasses is that a standard magnetic compass does not require re-calibration, which electronic compasses do on a frequent basis. I have had to recalibrate the 60CSx and the compass in my Suunto X6 when navigating in whiteout blizzards and fog - inconvenient to say the least. Thankfully, I have learned to recognize the signature misbehavior of a de-calibrated electronic compass quickly. The easiest solution is just forget about the electronic compass and use a real compass (the electronic compass in my plane had an automated recalibration, but I still had the back-up regular magnetic compass, as is required).

 

Still another point is - look at the price difference between the sensor and non-sensor versions of GPSRs. The difference between the 60Cx and 60CSx, for example is far greater than the $10 for a simple baseplate compass which is far better.

 

The OP didn't mention the barometric altimeters, but this has come to be one of my greatest complaints in those Garmin GPSRs that have them. Garmin has them turned on all the time - there is no way to have the 60CSx and 76CSx, for example, show only the GPS-derived altitude. If the "calibrated" altitude shown by the barometric sensor is within 1200 feet, the Garmin units will not autocorrect to the GPS-derived altitude. This means that if the barometer reading shifts by, say, 0.3 inches from day to day (equivalent to 300 feet error), the Garmin units will happily display this erroneous altitude, unless you go through the recalibration procedure. Since the GPS-derived altitude is within 1.5x the horizontal error estimate of the true altitude, the GPS-derived altitude will rarely be off by more than 30 feet, and usually much closer than that (remember that the USGS accuracy specification for 1:24k maps is 1/2 contour interval, so about 20 feet on most maps, putting you in the same ballpark as the maps). To have the altitude displayed on a Garmin "S" unit, you have to recalibrate the altitude to the GPS-derived altitude (3rd choice on the menu) or be at a known, surveyed altitude point on a frequent basis.

 

Worse (for someone like me who travels to polar regions frequently), since the atmospheric pressure in polar regions (above 70 deg latitude north or south) is significantly lower than the surveyed altitude would indicate, the Garmin "S" units display an altitude that is significantly different from the surveyed altitude when you get above 7000 or 8000 feet. At those latitudes and altitudes, the difference between the GPS-derived altitude and the pressure altitude is greater than 1200 feet, so the Garmin units "feature" of auto-calibrate resets to the barometric value within a few seconds of attempting to set to the surveyed altitude or to use the GPS-derived altitude. At the 12,100 foot High Camp on Mt. Vinson in Antarctica, for example, the 60CSx insisted on resetting to 13,500 feet and would not accept the correct altitude.

 

Ok, that doesn't affect most people, but it is a real flaw.

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:D O.K., I concede.

The electronic compass is a real battery hog.

So if you want to go out for a three day stint with only two brand spangley new batteries,

DON’T get on with the EC.

After all, even if you turn it off, are you really sure??????

And two, all the flaws make it completely unworthy for someone hunting an ammo can along a hiking trail in a park. :D

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Can someone clarify one point for me?

 

Right now, with my Garmin Lengend, I have to be walking before the compass (and arrow) register a change in direction. With the electronic compass the arrow will always be pointing in the right direction whether or not I'm moving, correct?

 

Thanks

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Correct. After you change batteries, you will have to "recalibrate" the compass, for it to behave properly, but that only takes a few seconds. I like having the compass in my Vista C, but sometimes it misbehaves and I turn it off, basically turning my Vista C into a Legend C. :D

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Can someone clarify one point for me?

 

Right now, with my Garmin Lengend, I have to be walking before the compass (and arrow) register a change in direction. With the electronic compass the arrow will always be pointing in the right direction whether or not I'm moving, correct?

 

Thanks

 

If your referring to the magnetic compass on a Vista, C, CX or the like then yes it will. The internal magnetic compass couples with the electronic compass that the Vista has and inturn it will hold its direction in place even if you set it down LEVEL on the ground. I have a Vista CX and I have used other models that do not have the magnetic compass and I prefer the Vista CX. All of the latest GPS units have an electronic compass that use's the Sats. to get a reading.

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I only now have a GPS with an electronic compass. It's not worth a boat load of money in my opinion if the two GPSs you are looking at are the same otherwise. If the price difference is $10, I'd say go for it. But this thing still flips all over hte place. I've decided next time I'm heading out, I'm going to bring along a real compass just for good measure.

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I fine the EC a great tool. I usually turn it on once I leave the trail, and leave it on until I get to GZ. In many cases, when say about 200 feet from the cache, you simply can't walk 20 feet in a straight line to get a non-EC GPSr to point to the general direction of the cache. Also makes trying to triangulate the cache much easier. I can eyeball a spot about 200 feet from the cache and just stand there, and get a bearing to the cache (making a mental note of what I see on the bearing). Then I can pick a different spot about 200 feet from the cache and get a new bearing. More often than not, the triangulation works and makes short work of the cache.

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The ring and the pointer are locked together because the relationship is fixed by the calculated bearing.

You mean "are not locked together", right?

 

To clarify, the compass ring always orients itself with heading up. The compass pointer always points to the destination waypoint.

Edited by DENelson83
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OP,

 

There is no reason not to get a gps with a compass, you can always turn it off, but I can assure you it is extremely useful and at least as accurate as my silva compass.

 

Regarding the "battery hog" statements. This needs to be further clarified, apparently it depends on which unit you use.

 

I have seen some tests done on the German forums that indicate compass drain is minimal on the new H series, something like 5%

 

http://www.naviboard.de/vb/showthread.php?...+Stromverbrauch

 

you can translate the page well enough to get the gist of it at http://babelfish.altavista.com/babelfish/tr

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The ring and the pointer are locked together because the relationship is fixed by the calculated bearing.

You mean "are not locked together", right?

 

To clarify, the compass ring always orients itself with heading up. The compass pointer always points to the destination waypoint.

If from your location the cache bearing is 30 degrees, the bearing pointer will always point at 30 degrees on the the ring. I called that locked. Are talking about he bearing changing because of error? On an EC GPS the N on the ring points North no matter how you point the GPS. People are trained to point their GPS at their heading on a non-EC GPS so the EC GPS seems the same when you point an EC GPS at your heading, but it doesn't have to be the same. The GPS is just a radio receiver and you can point it any way you want.
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OP,

 

There is no reason not to get a gps with a compass, you can always turn it off, but I can assure you it is extremely useful and at least as accurate as my silva compass.

 

Regarding the "battery hog" statements. This needs to be further clarified, apparently it depends on which unit you use.

 

I have seen some tests done on the German forums that indicate compass drain is minimal on the new H series, something like 5%

 

http://www.naviboard.de/vb/showthread.php?...+Stromverbrauch

 

you can translate the page well enough to get the gist of it at http://babelfish.altavista.com/babelfish/tr

I agree with this totally. To me the only consideration would be an economic one. If the price difference is meaningful to you, then by all means get the non-EC model. I am sure you will find lots of caches with it. After using a model with an electronic compass for 3+ years I won't have another handheld without one. I DO carry a magnetic compass and spare batteries, too. If I was in survival mode I would turn off the compass to save batteries, but I have cached for hours with it turned on and still showed full battery strength on the meter. I don't find battery usage to be an issue for normal geocaching.

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I had two GPS's without electronic compasses and supplimented directions using a magnetic compass.

I am VERY proficient in use of a map, compass, GPS, and UTM grid.

 

BUT when I bought my GPSMAP 60CSx last year I decided to "go for it" and get the model with the electronic compass.

 

I like it and am glad I did buy it.

 

The short of it is that it allows me - with the push of one button - to stand still and still have the GPS's compass point to the destination waypoint without bothering to pull out a compass, reading the bearing off the GPS, setting the compass, and boxing the needle. Its a matter of convenience for me.

 

I'm geocaching - not risking my life trudging through wilderness or surveying property lines. The 60CSx's compass is accurate enough for my needs AND is very easy to turn on/off.

 

For the roughly $30 it costs I think the electronic compass is well worth the price. Still, if you are heading out into the wild, make sure you ALWAYS bring along a map and compass and know how to use them.

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I have seen some tests done on the German forums that indicate compass drain is minimal on the new H series, something like 5%

I can't speak for the H models, but can confirm it for the 60CSx. On the 60CS the current drain is increased by about 50% when the compass is turned on; on the 60CSx the current drain is minimal (possibly 5%, but certainly no more).

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What is the downside to an electronic compass (i.e. what makes it a PITA)?

 

I'm in a similar situation as the OP, and ever since my first GPS I've wanted an electronic compass, but now I'm second guessing myself.

I've never had a problem with it. The compass is the RING on the navigation page, it is NOT the POINTER. When people complain about the "compass", they usually mean the pointer, not the actual compass ring.

 

The pointer can appear to be acting erratically, but it's not. It's just doing exactly what it's supposed to do: determining your position, the target position, and then aligning the arrow to point towards it. But once you get close to the cache, and enter the "error zone", the arrow can start appearing to behave erratically. Because of the normal GPS error, the unit may calculate your location as being west of the cache at one moment, and east of the cache a few seconds later. The pointer is just show the results of those errors. If you used a hand-held magnetic compass, it would show the same wacky behavior. But the difference is that if you had a hand-held magnetic compass, you would have already dropped it in your pocket by now. But since the pointer is right there on your GPS, you continue to let it lead you long after you should have put the GPS away and started searching for the cache.

 

Another reason people can think their pointer is behaving oddly is when they accidentally set it to Course Pointer, instead of Bearing Pointer. The Course Pointer tries to keep you on an imaginary line between your starting point and ending point.

 

Of course, there are a tiny percentage of unit that actually do malfunction. But in the vast majority of cases, it's just a matter of people not understanding what's going on in their units.

 

"What is going on in their unit?" I'm new at this GPS stuff. But sorry, but no one has explained this as yet. I assume everyone has passed simple geometry and knows that is takes TWO points to determine a "pointer" and electronic compass bearing -or- it takes a base known direction. My #1 question is what is the GPS doing when you "calibrate the compass" rotating at one point? I assume it is finding a base direction using satellites (SAT)? How does it do this?

 

Ok, the #1 job of the GPS is to use SAT triangulation to determine ONE point. Easy, simple and accurate.

 

Does the electronic compass use multiple location points? If so, are the points used along your recent path (or does it remember the compass calibration point)? Do you have to move? If so, how fast do you have to move or far apart do the points have to be.

 

Lastly, how often or what priority does the GPS unit give to calculation a bearing vs. GPS point?

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My #1 question is what is the GPS doing when you "calibrate the compass" rotating at one point? I assume it is finding a base direction using satellites (SAT)? How does it do this?

There are two sensors on two axis at right angles that measure magnetic field strengths. I'm guessing that when you rotate the GPS is looking for the peak outputs of the sensors and remembers the values. The peak values would change with battery strength. You are right, the SATs won't give you a direction. It can guess that you went in a straight line from the last point it measured, but is just a guess.
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My #1 question is what is the GPS doing when you "calibrate the compass" rotating at one point? I assume it is finding a base direction using satellites (SAT)? How does it do this?

There are two sensors on two axis at right angles that measure magnetic field strengths. I'm guessing that when you rotate the GPS is looking for the peak outputs of the sensors and remembers the values. The peak values would change with battery strength. You are right, the SATs won't give you a direction. It can guess that you went in a straight line from the last point it measured, but is just a guess.

I think you are right; I would guess they use the peak excursions to adjust for the relative amplitudes between the two sensors, and for any offsets in each sensor.

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I ran some battery tests awhile back on my 60CSx, using a new set of Rayovac Hybrid batteries.

 

For my reference run, I turned ON the compass, and WAAS and left it running. With these particular batteries, I got 16:18 (hrs:min) of runtime.

 

Turning OFF the compass and rerunning this same setup, I got a 2.9% increase in run-time (16:47).

 

Forcing the backlight to stay on at 50% brightness resulted in a 10:30 runtime, or a 35.6% decrease from the reference run.

 

Forcing the backlight to stay on at 25% brightness resulted in a 12:38 runtime, or a 22.5% decrease from the reference run.

 

So, yup, the compass does decrease the runtime by a bit on the 60CSx, but not nearly as significantly as the backlight.

-RenHoek

 

{edited to correct 25% backlight results}

Edited by RenHoek
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I read about a magnetic compass as addition to my geocaching tools when I was using primarily a eTrex Legend ("old blue"; no electronic compass). But I simply could not figure out how to get that to work. The compass points to magnetic north, which is 12 to 15 degrees off true north for me, and that tells me when my Legend is NOT pointing in the right direction if I pay close attention to the alignment of the letters on the compass circle in contrast with that same alignment on the magnetic needle compass, which I can't concentrate on while I am looking at the pointy arrow on the GPSr showing me where the cache is. Meanwhile the magnetic compass points one way and the Legend points some other way, which I know is normal ...my head hurts just thinking about it. :)

Now that I have my 60CSx, it integrates all this into one unit and does it all this for me whenever I have it turned on. Even if it is not the most accurate pointer to true/magnetic north, it gets me to the cache quickly.

 

My experience with battery drain is similar to RenHoek's report.

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I read about a magnetic compass as addition to my geocaching tools when I was using primarily a eTrex Legend ("old blue"; no electronic compass). But I simply could not figure out how to get that to work. The compass points to magnetic north, which is 12 to 15 degrees off true north for me, and that tells me when my Legend is NOT pointing in the right direction if I pay close attention to the alignment of the letters on the compass circle in contrast with that same alignment on the magnetic needle compass, which I can't concentrate on while I am looking at the pointy arrow on the GPSr showing me where the cache is. Meanwhile the magnetic compass points one way and the Legend points some other way, which I know is normal ...my head hurts just thinking about it. :)

Now that I have my 60CSx, it integrates all this into one unit and does it all this for me whenever I have it turned on. Even if it is not the most accurate pointer to true/magnetic north, it gets me to the cache quickly.

 

My experience with battery drain is similar to RenHoek's report.

 

You should have a setting on ole blue to set to either magnetic or true. The 60 come set to true by default.

 

Now, with both set the same, see what they read.

 

Then also take a magnetic compass (preferably one where you can set the declination on) and place all three on the floor parallel and touching each other.

 

NONE will read correctly, due to magnetic interference.

 

Separate them by a reasonable distance but keep them parallel, and all will read correctly and the same.....my 76CS, 76CSx, and magnetic compass do.

 

That's a good way to realize just how sensitive the electronic compasses are to metal objects and other magnetic interference.

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