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FSX GPS quirk?

robystar

robystar

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5,214
Hi,

(I could not decide where to post this question, hence my posting it here so I will not mind if it is placed somewhere else:)).
After having been modelling for a while I felt like flying once more.
So I took the default Cessna 172 and took off in real time (early morning) and real weather (dense fog) conditions in spite of ground control denying me request as airport was IFR only. (I am telling you this because it may have some bearing on the problem or not).
10 minutes later, turning back, trying to follow the coast line and to find my position on the GPS, I landed on the grass to the right side of the (invisible) runway.
The GPS apparently got me confused or maybe I confused the GPS because it is still confused!
On the screenshot I am on the center of the runway and heading 81. How come the GPS is showing aircraft with heading 261 and how come it shows the runway to the left and another oblique runway present only in the default airport?
I did change the location of the airport to match the real world coords but it looks as if the GPS is ignoring this.
Does anyone have some explanation for the wrong heading indication and (if not automatic) how to update the GPS with the new info?
Fyi, I found no double airport entries.

Roby

PS Tried to do a search for GPS problems but you can not search for GPS. So if you want to see this thread again after a while you would have to search for 'quirk' :):rolleyes:.
 
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Hi George,

No I did not.
But in the meantime I found out it is the slew command that makes my GPS go haywire.
I unslewed, changed aircraft and it was OK again.
Then I slewed the aircraft 1m to the left and watched my aircraft on the GPS which showed a heading of 348º this time perpendicular to the runway!???!
Update: weird! I changed to the default 737 and the gps stayed wrong. I then changed again to the CRJ700 and the GPS showed the right heading again.

PS I do have an orphaned ILS some 30 miles NW of EBOS:o.
 
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The GPS is actually showing your ground track (that's the only way it can be as there's no compass in the GPS unit in real life) so if you slew the aircraft in a direction other than the one the aircraft is facing the GPS will give you a Track read out for the ground track you've covered.
Similarly if you use it in a helicopter and fly backwards the track will read the opposite of the aircraft heading. In a fixed wing aircraft with a strong crosswind you could see a difference of 10 degrees or so between heading and track.
 
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Hi,

Tks, I was already wondering whether that was a 'never noticed before' default GPS behavior as it occurs everywhere.
Except for one thing though.
How come the runway is not depicted in the right place?
And a couple more things I recall:
- how come the GPS does not change back to normal when changing to a default B737 but does when changing to a CRJ700?
- and how come when I slew just 1m to the left (and nothing else), I see the GPS changing headings as well?
 
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- how come the GPS does not change back to normal when changing to a default B737 but does when changing to a CRJ700?
Click to expand...

It may just be to do with the way FSX's updating the variables when you load a new aircraft, some don't seem to reset themselves on the first reload until you move the aircraft.

- and how come when I slew just 1m to the left (and nothing else), I see the GPS changing headings as well?
Click to expand...

Well it should read that as a ground track in the direction it's moving so it'll change. Again, it's not Heading, it's Track, Heading is the way the aircraft is pointing, Track is the line it's tracing across the ground. Unless the GPS has a built in compass it has no idea what your heading is, only your track.

Not sure about the runway, although if you're in slew mode I'm not sure if the map updates as often as it does normally which might be a factor.
 
Hi,

And thank you so much. Once you know the GPS shows your track and not your heading, then the rest becomes self-evident.
As for the blue/white runway image being off, I noticed it also happens on many default airports both with the Garmin 500 and the Garmin 1000 (but then, I should have used the VOR/DME).
 
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