I can see track and ground speed. But I can’t see how GPS can give you heading and attitude.
Everything you want to know and more
Thanks, but what I could read without signing in was over my head. Can you dummy it down for me. How can GPS tell if the plane is pitched up or down, wings level or not, or which way the nose of the plane is pointed?Everything you want to know and more
GPS aided attitude and heading reference system using MEMS sensors
Nauga,
unfiltered
The GPS is not doing that, vehicle velocities and accelerations (3 axis) from the GPS are used to augment the inertial measurement unit that senses attitudes with unknown errors. In general you can't measure attitude (very well, anyway) with a GPS and you *can* estimate attitude without a GPS, but you can get a better estimate of attitude using the GPS with other attitude systems.
Augment how? Does the GPS actually input info that will change the pitch and roll indications on the AI?
Yes, indirectly. Attitudes are not measured and output by the GPS, the linear rates and accelerations provided by the GPS are part of filter that calculates (actually estimates) attitude when/because the simple inertial attitude measurement (estimate) is inaccurate or too low a sample rate.
I can't say about a splitter but it does have an internal antenna which was good enough in my installation. There are provisions for an external antenna, but I did not use one. My G5 also gets GPS data from two other sources, and while I have my suspicions I honestly don't know which source it uses for the augmentation.
You might find (I sure have) that a lot of shops wouldn't have known the details listed above anyway. They generally tend to be quite unaware of the engineering that happened behind the scenes at the manufacturer
"How's it work?"
Couldn't be more true. Honestly I'd just be happy if they said "I dunno, I just follow the manual" but that'd be a lie too, because they all to often don't.
So if GPS, by tracking you, sees that you are turning left, it will assume the wings are rolled to the left? And if your ground speed is increasing it will assume the nose is pitching down? Ground speed decreasing, assume the nose is pitching up?
It's far more complex than that, and I'm not confident I can simplify it enough without making some glaring error that's going to further confuse the issue. GPS, accelerometer, and gyro (solid-state these days) data are all collected and used to partially populate a model of the system (in this case a 3-variable attitude state-space model) which is then numerically solved which will provide (among other things) an estimate of the attitude of the airplane that is more accurate than that measured by the inertial 'attitude' sensors alone. While the GPS inputs may resolve into e.g. 'moving left so must be banked left' etc, the model assumptions are not (or 'should not be') that simple, and the system, if implemented correctly, can handle unusual attitudes.
Ok. It still doesn't completely pass the logic with me, but it's far from the first I just didn't have enough Bytes between my ears to grasp the logic. Thanks for taking the time to take a stab it.
Gps recievers are a few dollars, and all they do is output a stream of character data regarding calculated data points. There are many apps for phones that will show the NEMA data streams and its quite impressive.
I get how the ‘display’ has a a lot of info on it. And it comes from different sources. Never heard of NEMA before. Googled, It’s NMEA. Looks to be basically a standard language so to speak. GPS can only tell it where you are. Then it can take the where you are report, compare it to the previous where you are reports, which are now where you were. And it knows the exact time between all the where you are reports. That can be used to give ground speed and vertical speed. And it can be used to predict where the next where you are report is likely to be. And that can be fed into the G5 and it can have a really great display with lots of very useful information on it. But what’s been said is that GPS can somehow be used to tell if the nose of the plane is pointed up or down and by how much. Or if the wings are level or not and if not, by how much. That’s what I’m having trouble with. That GPS provide attitude information.
Yeah, I know, see my post #9. But it still isn't sitting right with me. In order to augment 'attitude' it has to be making some kind of determination on what the attitude of the plane is. I simply can't see how GPS could know where the nose of the plane or the wings are. Well, they're where the plane is of course, but which they are pointed.
If the GPS can't determine attitude, how can it augment the attitude display. Or maybe I should say, how can the SEPARATE computer use GPS to augment the attitude display if GPS is incapable of determining attitude.
Altitude. Not position. I’m talking about attitude. I’m saying I don’t see how GPS could know if the plane was pitched or down or if the wings were level banked.
You keep saying attitude and everyone understands that the final result is attitude, but what you're missing is that time/space/position information from a GPS can be used with the methods discussed in references posted here to refine an attitude estimate provided by other methods (e.g. inertial reference units). The GPS does not provide attitude, it provides data that can be used to improve an attitude estimate. What you might think of as your no-**** attitude is really just a measurement or estimate of attitude from a variety of sources, each with some inaccuracy or uncertainty. You can use additional sources, some of which may not be an exact corollary to the thing you're trying to measure but with known physical relationships to them (e.g. equations of motion), to improve the accuracy or decrease the uncertainty.
