Electronic Compass

[ksat]

All,

 

I thought I'd turn to the pro's and the experienced for this queestion...

 

I'm looking to buy a GPS unit for multiple purposes. Primarily, caching and ballooning. That's right - Hot Air Ballooning! I'm a student pilot looking to buy a balloon and a GPS will be a must - so I want to get a decent one without breaking the already broken bank!

 

However - I have a concern about the types of electronic compass many units have. From what I understand, for most (if not, all) of the Garmin GPS units, you must hold the unit level - flat. For many of the Magellan units, you can hold them 'naturally' as they have a 3-axis electronic compass. While I like both units, certain Magellan units are more affordable but appears to have more issues than the Garmin units (which are more expensive). This issue is can be critical because the GPS will be mounted to an upright on the balloon - thus, not horizontal which will lead to inaccurate readings.

 

Can anyone speak to this 'issue' and suggest a device which is best suited? Prior to Christmas, I was looking at the Magellan SportTrak Color Topo (which I can't seem to find anymore). Now, while Magellan still looks like a good option, many of your postings about the Magellan units have me worried and thinking about a Garmin - 60CS comes to mind, but, does get a bit expensive. Ideally, I'd like to stay around the $300 range. Another critical feature is detailed road maps - so we know where we are in the air...Altimiter also required. I think most have this though.

 

Thanks...

KSAT

Edited December 27, 2005 by ksat

[+Klemmer]

I'm very happy with my Magellan Meridian Platinum. I'm not sure if it is in production anymore or not. I THINK the Explorist Series was designed to replace the Meridian Series, but.... In any case, it is still on Magellan's website, and a quick Google brought up lots of places still selling it.... From what I have read on these boards, I would not YET buy an Explorist 600. I hope my 3+ year old Plat hangs on a while. Seems like lots of issues with it. They'll get solved eventually, but why look for trouble....

 

Your answer: The electronic compass is great. I have very few issues with it. Once in a while (maybe every month or two), I have to run a re-calibrate on it (takes about 30 seconds, and you need somewhere flat and non-metalic). It DOES work fine at any angle (even up / down). I think the recal is needed when I have had it laying too long on something metalic or near DC power wires (like on the dash of the car). Of course, when you have it moving (like on the balloon), the GPS system will give you a north bearing without the compass. It's when you are standing still that the compass is great to have. On the balloon, will you be far enough away from the burner & tanks? I'm just guessing, but even 6 - 8 feet away from a big hunk of steel could be a problem for ANY compass. Isn't there an installed / corrected / checked compass on on board the balloon? (I'm a pilot, but not of balloons!).

 

For geocaching, VERY nice to be able to stand still and say - "that way", while the other "non-compass" cachers are wandering around. Also works that way wel for taking a bearing to a landmark, like a peak, if you do serious hiking. I always carry a decent compass for back-up, however.

 

With a 256MB SD card, lots of room for maps, waypoint files, track files, etc. As many waypoint files as you care to have (with 500 waypoints each), which might be many, if you are navigating from a balloon, I guess....

 

Have fun!

[+Klemmer]

Ahh... altimeter. Not on the Meridian.. it has a barometer. Big difference. And the GPS altitude might not be accurate enough for a balloon... dunno. You might need a small 'hiker" altimter or something, if you have to be able to put in the altimeter setting (correction) from ATC, and then have something reasonable.... Are there FAA requirements for calibration, etc.?

[ksat]

Thanks for the reply!

 

In the balloon basket, typically, you'll want the GPS at eye level. The burner is right above your head - about 1' - 1.5' away. The tanks, typically stainless steel, Aluminum, or Titanium, are on the bottom of the basket, lying down or standing up - about 3' away. Will this really cause a whole lot of interference with the GPS? I wouldn't expect it to, but, I don't know... really.

 

There are no FAA regulations pertaining to the calibration of Balloon navigational instruments that I am aware of - this is primarily due to the nature of the aircraft. It is considered a lighter-than-air aircraft and unguidable. The only exception is that of the altimeter/variometer. But, a FlyTec 3040 will resolve that issue and several more for me!

 

I too have seen plenty of Meridians around...and I have seen the Explorists 500/600/XL models all over the place. Magellan's website is TERRIBLE for removing discontinued products from their lists of products so it is very difficult to determine what is new and what is old.

 

Does your Platinum have the 3-axis Electronic Compass that Magellan has been advertising lately? I keep reading about this feature but am unable to find any reviews about the accuracy compared to a "standard" electronic compass that operates on 2-axis.

 

Thanks again,

KSAT

Edited December 27, 2005 by ksat

[peter]

For ballooning I'd be more concerned about the altimeter function. Although all GPS receivers do provide altitude, the GPS measurement is subject to considerable fluctuations so using it to determine your current rate of climb or descent is less than ideal. The Garmin models with pressure sensors do a good job of integrating the GPS and pressure-based altitude measurements so they provide better readings than either type of instrument can do on its own. Although the Garmin "Jumpmaster" features are mainly geared towards parachutists, some of them would also be useful for ballooning.

 

Regardless of the GPS, I'd want a regular compass anyway that isn't subject to failure of electronic components or power. That would also let you mount the compass and compensate for any local magnetic materials so you wouldn't need to recalibrate every time you change batteries in the GPS (most batteries are somewhat magnetized).

[+Klemmer]

Yes, the Meridian Platinum is 3-axis, according to Magellan website & my manual. It works well. I never worry about keeping it flat, and it gives me believable numbers, except in a car, or when I walk over a buried pipleline on a trail (that was fun the first time - BIG compass swing I happened to see, stopped, looked around, YEP, pipeline crossing under the trail!), etc. I can't speak to the exact bearing accuracy, but it has been fine for finding caches! You can set it for Magnetic or True, or you can turn it off ("Use GPS Course). Batteries last longer when it is off.

 

I have flown many aircraft with 3-axis flux-gate compasses (to use the technical term), and never had any problem, at any flight regime (inluding inverted!) except that one time taxiing past the huge blimp hanger at the old Hamilton AFB.... We had a "recalibrate" button, which took about 10 seconds or so. Of course, the system probably cost a couple million taxpayer dollars..... These things don't have moving parts, by the way. Just three "sensor loops" as I understand it.... Might be one reason the Meridian Platinum is a little bigger & heavier than my Etrex Venture, for example. Not that it is a problem...

[+Alan2]

Isn't there a web page for balooning? I'm sure others in your sport have tried diferent GPS's that would have more pratical experience with different models used in your sport.

[+JohnnyVegas]

Why not just buy a Marine compass that you could mount on the balloon basket. As far as an altimeter, why don't you ask your fight instructor what requirements the FAA may have.

[ksat]

Well - most pilots use a Garmin eTrex. But, I would personally like something with more capabilities in and out of the balloon. The FlyTec will be the primary source of information for altitude and such. The GPS will be a comparitive device.

 

My main concern was with the difference in electronic compasses in each GPS. Like I said, the Magellan's appear to utilize a 3-axis electronic compass. The Garmin's don't specify but appear to have problems when being held in an upright position. Anyone have any experience with this?

[+av8ndv8]

Another balloon pilot here.... We use the calibrated altimeter in our instrument pack so don't need that function from a GPSr. But it's interesting to see the vertical profile of a flight along with your track afterwards, though.

 

GPSrs with built-in electronic compass only use them while standing still or moving very slowly. My Garmin 60CS kicks into the satellite data over 2mph or so. All GPSr units will show compass data as long as you're moving and it's always more accurate than any built-in compass.

 

That said, the built-in Garmin compass is totally worthless doing what you want. It's way too finicky about being held at JUST the right angle almost flat. Held vertical it will go 180* out and totally confuse anybody looking at it. Worse, on any but the arrow page it gives no indication that it's screwy.

 

The Magellan 3 axis compass is much, much better, almost excellent. BUT, before having this lousy built-in compass, I never missed having one because I was almost always moving. So don't let Garmin's godawful compass sway you from getting the best brand of GPS.

[peter]

We use the calibrated altimeter in our instrument pack so don't need that function from a GPSr. But it's interesting to see the vertical profile of a flight along with your track afterwards, though.

 

GPSrs with built-in electronic compass only use them while standing still or moving very slowly. My Garmin 60CS kicks into the satellite data over 2mph or so. All GPSr units will show compass data as long as you're moving and it's always more accurate than any built-in compass.

True on the altimeter but 1) redundancy of instruments is frequently a good idea, and 2) if a weather front moves through then the previously calibrated altimeter will read incorrectly while the Garmins with pressure sensors can use the time-averaged GPS readings to compensate for the weather-related pressure changes. Of course most balloon flights are done in excellent weather conditions so the second point may not be important for many balloonists.

 

In most circumstances I agree that the GPS-based compass works very well even when moving quite slowly. But one difference between it and a magnetic-based compass is that the directions are shown based on your direction of movement rather than based on the direction in which you're facing. E.g. if you're flying very high in a balloon with little wind you might not be able to accurately see in which direction the balloon is drifting. In that case the two compass indications give you different and complimentary data: the GPS-based compass may tell you you're drifting to the SW while the magnetic compass would tell you in which direction to look for the distant mountain that you know is to your west.

So I can see a use for a magnetic compass on some balloon flights, but I'd still prefer one that's separate from the GPS receiver. Both from a redundancy standpoint as well as providing additional information by being able to get both types of compass readings at the same time.

[ksat]

The Magellan 3 axis compass is much, much better, almost excellent. BUT, before having this lousy built-in compass, I never missed having one because I was almost always moving. So don't let Garmin's godawful compass sway you from getting the best brand of GPS.

Nice to see another balloon pilot in the group. Hopefully soon I can take the title as well - for now, I must stick with "student/crew."

 

Either way, its in my future and I don't want to get stuck trying to read a compass heading thats 180 degrees off and try to mentally compensate for it.

 

Both brands have their pros and cons... Talk about a hard decision.

 

Maybe I'll wait until '06 to see what both release. I understand some of the the Meridian series will be discontinued as some of the Garmin's have their issues (and no 3-axis compass).

[MagicTogether]

It's been awhile since I piloted a ballon! I found that a pair of binoculars with a built-in compass was excellent for taking a bearing on distant objects. There are several available in the marine supply stores.

 

A GPS is most excellent for determing which way you are drifting at different altitudes. You can bump up or down to "hopefully" find a bit of air moving the direction you want to go.

 

I'll second av8ndv8's remarks about use of a proper altimeter. With the "standard" aviation altimeter you can know your altitude accurately in order to avoid controlled airspace and to properly announce your altitude when necessary. You ought to be able to purchase a used one at one of your local instrument shops or aviation suppliers at a considerable savings over new.

 

I also concur with av8ndv8 about the electronic compass in a handheld GPSr, it isn't worth the hassle.

 

MagicTogether - Alaska

Jim (ATP, B727, L188, YS11, C46, AMEL&S, Commercial Hot Air, CFI, etc...)