Altitude

[The Spook]

GPS signals allow for calculation of position, x,y & z...Elevation is available.

I never said they didn't, please re-read my post. What I said was that it wasn't designed to give 3D positioning (because it wasn't), and that it is not very good at it (because it isn't).

...and the altitude readings are very good. It's normally less than +-10 meters. That's good enough for me. I know the exact altitude at home, and TomTom always is correct within a few meters. Very good!

How do you know they are correct?? If they are +/- 10 meters it is a happy accident, because the horizontal accuracy specification is greater than that and vertical positioning accuracy (typically not quoted by manufacturers because it looks bad) is typically 1.5x - 2x the horizontal figure.

Rcacs, as a pilot you must be aware that GPS is never used for altitude. There is a good reason for this, it would be suicidal. If planes could reliably get a 3D position from (uncorrected) GPS, they would. They use an altimeter because they can't.

At teh end of the day it boils down to the mathematics of calculating the position. To achieve z-level accuracy approaching x/y accuracy is a pipedream. I use GPS receivers that can achieve 10cm accuracy horizontally, vertically they struggle to get 50cm.

If you are interested in learning more about the subject, there is a good starter to the topic here http://weather.gladstonefamily.net/gps_elevation.html More precise descriptions go straight into the realm of hyper-maths!!

 

[dhn]

Did you see the FAA in the States has just started using GPS signals instead of ground radar for routing commercial planes. Apparently, allows for slightly more direct routes resulting in savings of some minutes and, these days, the important item of saving fuel and $$$.

 

[rcacs]

All very good and vaild points, no doubt. My original question mearly revolved around a reading for altitude to satisfy curiousity and "one more bit of semi to sorta useless info". My pals Garmin Zumo provides altitude, mearly based on location, not pressure. Therefore, there should be no reason that TT cant provide the same.

So if I am scootin along somewhere in Montana, or Quebec, or where ever, and my brain all of a sudden wonders what the approx altitude is, I could find out by looking at my TT. If the reading said 1200ft, and it was actually only 1100ft, I wouldnt sweat it at all.

Thanks for the input tho,

Cheers

 

[The Spook]

My original question mearly revolved around a reading for altitude to satisfy curiousity and "one more bit of semi to sorta useless info".

In which case, installing tripmaster will do it. It will show an altitude reading.

Therefore, there should be no reason that TT cant provide the same.

No, there isn't. It is a case of won't, not can't.

You could write and ask them to add it in future versions (as many have before). But, as I said previously, I wouldn't hold my breath while I waited for it to happen!

 

[rcacs]

Thanks again for your input. I seen the posts regarding the install of Tripmaster, it looks abit too daunting for moi. O well.....

Cheers!

 

[Statman]

Thanks again for your input. I seen the posts regarding the install of Tripmaster, it looks abit too daunting for moi. O well.....

Cheers!

It really is not that difficult if you use the install flash demo. It took me like 5 minutes max..