Alternative magnetic compass

On Friday, October 30, 2015 at 5:00:02 PM UTC-4, jfitch wrote:
On Friday, October 30, 2015 at 1:03:52 PM UTC-7, Mike the Strike wrote:
I should also remind everyone that GPS-derived bearings only work when you are moving with respect to the ground. Just remember this if you're stationary or even moving backwards in wave.

Mike

There are GPS compasses that do not depend on motion for operation. Doubt anyone has one in a glider though.

I don't think there is such a thing as GPS compass, regardless if you are moving or not. GPS is measuring your position, it has nothing to do with measurement of magnetic field.

In article ,
, says...

A sailplane's Flight Manual usually requires a magnetic compass (or an
aviation compass)as minimum equipment. Well, panel space has become
less available and you are seeing fewer sailplanes with panel or
glare-shield mounted 2.25 Airpath C2xxx or PAI-700 aircraft specific
compasses.

Anyone have a "point" to an off panel compass that might meet FAA
scrunity? Unfortunately the Cook compass manufactured by COBB-SLATER
Instruments Co. Ltd is no longer available.
http://compassmuseum.com/aero/aero.htm#COOK

Probably, a magnetic compass is the last instrument used by a
competition pilot. Most competition sailplanes have 3 or more separate
GPS engines and it is very simple to have them on independent battery
sources. What would be the "penalty" if your sailplane failed a FAA
"courtesy" ramp inspection because it lacked a magnetic compass?

Does a F-35 Lighting II joint strike fighter has a magnetic compass?

I'm sure it does, but it'll be an electrical one - that is, one using a
magnetometer.

Makes me wonder, how would such a, cheap but obviously not FAA approved
device go, for gliders...

https://duckduckgo.com/?q=arduino%20magnetometer&t=lm

--
Duncan.

On Friday, October 30, 2015 at 2:20:55 PM UTC-7, Andrzej Kobus wrote:
I don't think there is such a thing as GPS compass, regardless if you are moving or not. GPS is measuring your position, it has nothing to do with measurement of magnetic field.

You can determine orientation (including direction) by using difference in 3D position of two GPS receivers (actually their antennae) mounted at a fixed displacement from each other. It's a bit more complicated than it sounds, as ideally, the two GPS receivers will have synchronized clocks and be using the same satellites for their position solutions. So, the receivers used are quite specialized.

On Friday, October 30, 2015 at 5:43:43 PM UTC-4, wrote:
On Friday, October 30, 2015 at 2:20:55 PM UTC-7, Andrzej Kobus wrote:
I don't think there is such a thing as GPS compass, regardless if you are moving or not. GPS is measuring your position, it has nothing to do with measurement of magnetic field.

You can determine orientation (including direction) by using difference in 3D position of two GPS receivers (actually their antennae) mounted at a fixed displacement from each other. It's a bit more complicated than it sounds, as ideally, the two GPS receivers will have synchronized clocks and be using the same satellites for their position solutions. So, the receivers used are quite specialized.

You are right, with two receivers and antennas far apart to mitigate the errors it is possible. Not something that one would want to mount in an aircraft.

On Friday, October 30, 2015 at 4:49:16 PM UTC-6, Andrzej Kobus wrote:
On Friday, October 30, 2015 at 5:43:43 PM UTC-4, wrote:
On Friday, October 30, 2015 at 2:20:55 PM UTC-7, Andrzej Kobus wrote:
I don't think there is such a thing as GPS compass, regardless if you are moving or not. GPS is measuring your position, it has nothing to do with measurement of magnetic field.

You can determine orientation (including direction) by using difference in 3D position of two GPS receivers (actually their antennae) mounted at a fixed displacement from each other. It's a bit more complicated than it sounds, as ideally, the two GPS receivers will have synchronized clocks and be using the same satellites for their position solutions. So, the receivers used are quite specialized.

You are right, with two receivers and antennas far apart to mitigate the errors it is possible. Not something that one would want to mount in an aircraft.

Been done. Check out Septentrio.
http://www.navtechgps.com/assets/1/7...0415_41_DS.pdf

On Fri, 30 Oct 2015 15:49:14 -0700, Andrzej Kobus wrote:

On Friday, October 30, 2015 at 5:43:43 PM UTC-4,
wrote:
On Friday, October 30, 2015 at 2:20:55 PM UTC-7, Andrzej Kobus wrote:
I don't think there is such a thing as GPS compass, regardless if you
are moving or not. GPS is measuring your position, it has nothing to
do with measurement of magnetic field.

You can determine orientation (including direction) by using difference
in 3D position of two GPS receivers (actually their antennae) mounted
at a fixed displacement from each other. It's a bit more complicated
than it sounds, as ideally, the two GPS receivers will have
synchronized clocks and be using the same satellites for their position
solutions. So, the receivers used are quite specialized.

You are right, with two receivers and antennas far apart to mitigate the
errors it is possible. Not something that one would want to mount in an
aircraft.

You could get a reliable heading with a fluxgate (solid state) compass
but not, as you say, with a single GPS receiver.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Wednesday, October 28, 2015 at 10:32:51 AM UTC-4, wrote:
A sailplane's Flight Manual usually requires a magnetic compass (or an aviation compass)as minimum equipment. Well, panel space has become less available and you are seeing fewer sailplanes with panel or glare-shield mounted 2.25 Airpath C2xxx or PAI-700 aircraft specific compasses.

Grob Astir CS does not require as minimum equipment.

https://www.dropbox.com/s/yjlrf96sbf...%20PM.png?dl=0

Please correct me if I am wrong, but doesn't the Butterfly S and the LX90XX with compass option both have fluxgate compass? One would think with these instruments we would not have to have a whiskey compass, that just takes panel/glare-shield space.


On Friday, October 30, 2015 at 5:24:17 PM UTC-7, Martin Gregorie wrote:

You could get a reliable heading with a fluxgate (solid state) compass
but not, as you say, with a single GPS receiver.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Friday, October 30, 2015 at 8:47:15 PM UTC-4, Jonathan St. Cloud wrote:
Please correct me if I am wrong, but doesn't the Butterfly S and the LX90XX with compass option both have fluxgate compass? One would think with these instruments we would not have to have a whiskey compass, that just takes panel/glare-shield space.

Perhaps LXNAV has the best chance of approval as the new LXNAV Compass module is advertised as a magnetic compass and sold as a separate (add-on) feature. A better job of "wordsmanship" than Air Avionics' Butterfly S.

If only the sailplane manufactures would release a Technical Bulletin stating these devices satisfy intention. But in today's world of government oversight and manufacture's liability risk, a snowball in hell has a better chance.

On Friday, October 30, 2015 at 5:47:15 PM UTC-7, Jonathan St. Cloud wrote:
Please correct me if I am wrong, but doesn't the Butterfly S and the LX90XX with compass option both have fluxgate compass? One would think with these instruments we would not have to have a whiskey compass, that just takes panel/glare-shield space.


On Friday, October 30, 2015 at 5:24:17 PM UTC-7, Martin Gregorie wrote:

You could get a reliable heading with a fluxgate (solid state) compass
but not, as you say, with a single GPS receiver.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

The Butterfly S doesn't have a compass option, it has the compass as a standard feature. The issue might be whether regulations require a TSO'd compass.