How come GPS reads different

I would be more worried about avoiding the big yellow things that are
the cause of all this, if it happens.


and about the poetry...

--
Thomas Borchert (EDDH)

Aluckyguess wrote:

I am getting over 500ft. difference and more.
"Matt Whiting" wrote in message
...

Aluckyguess wrote:

How come the GPS reads a different altitude than the Altimeter?

For many reasons. The main reason is that they derive altitude by two
completely different methods and this inevitably introduces errors. Then
each method has its own inherent errors.

Even two altimeters side by side won't read the same altitude other than
by accident.


Matt



GPS altitude is not accurate. That is why you need to have a baro sensor
included as input to a IFR approved GPS.

--
Regards, Ross
C-172F 180HP
KSWI

GPS is most accurate when your position is surrounded by satellites. In
the horizontal plane, that is usually true. In the vertical direction,
you always have satellites above you, but none below you. This also
makes altitude slightly more difficult to resolve.

http://gpsinformation.net/main/altitude.htm
--
Gene Seibel
Gene & Sue's Aeroplanes - http://pad39a.com/gene/planes.html
Because we fly, we envy no one.

Ross Richardson wrote:

GPS altitude is not accurate.

.... except when it is, which is most of the time.

That is why you need to have a baro sensor included as input to a
IFR approved GPS.

That baro input is used as a cross-check for gross errors, to assist
RAIM. It does not "correct" inaccuracy, and thus is irrelevant to the
normal GPS altitude readout.


- FChE

Gene Seibel wrote:

GPS is most accurate when your position is surrounded by satellites. In
the horizontal plane, that is usually true. In the vertical direction,
you always have satellites above you, but none below you. This also
makes altitude slightly more difficult to resolve.

http://gpsinformation.net/main/altitude.htm

It's true that GPS vertical accuracy is worse by about a factor of 1.5
to 2 than horizontal accuracy. But despite this, GPS vertical accuracy
is still better than using barometric pressure when you're at a
significantly different altitude than the reference point giving the
barometric calibration.

The continued use of pressure-based altimeters is for consistency and
reliability - not accuracy.

Jim Fisher wrote:
"Tauno Voipio" wrote in message


Actually, if Earth would disappear with all its mass, GPS would
get unusable, as the satellites would continue out of their
tracks due to the lack of gravity pull.

Yeah, but they'd work longer than a pressure altimeter so I think we should
still adopt GPS altimeters in case this ever actually happens.

Good idea! It's always smart to be prepared. I always carry a
towel with me whenever I fly. Just in case.

John Galban=====N4BQ (PA28-180)

Thomas, I've a complete off-topic question.
I see you fly from Hamburg, is there any chance you ever been to
Borkum(EDWR)?
I'm send on a reconnaissance mission tomorrow to check out if the place
is oke for our vacaction.

Any info is helpfull,
Kees (EHSE)

I see you fly from Hamburg, is there any chance you ever been to
Borkum(EDWR)?


Yes, I have been there. IMHO, while nice, it is not the nicest of the
East Frisian Islands. I would prefer Juist, one further down. Baltrum
is great, too, if your plane is REALLY short-field capable. Borkum
would be next on the list, with the others being much more touristy due
to a lot of one-day visitors.

But this all depends on what you want to do there. Borkum has car
traffic, the other two don't. On Juist, the field is far away from the
village, and you'll need to take the horse-drawn coach. Bicycle rental
in the village only.

--
Thomas Borchert (EDDH)

Thanks for the info.

The problem of visiting the other islands is not the short field
capability of my plane(it being a Rallye), but my lack of German.
According my Bottlang Borkum is the only one with English R/T.

The plan is to have a vacation for a week or so in August(when the sea
temp. is a bit up) and use Borkum as a base to fly from to other nearby
fields in Germany or maybe Denmark.
To be honest, Helgoland is high on my wish list.

Happy landings,
Kees.

According my Bottlang Borkum is the only one with English R/T.


I wouldn't care about that. Just fly in and talk to them in English.
Also, if you want, I can find out more by calling them. Just tell which
fields you are interested in. Use

thomas (the sign of signs) aeroversand.de

to send me an e-mail...

Our TB-10 won't do Helgoland - otherwise I'd have been there a long
time ago. I would have some recommendations for Denmark, too. Oh, and
if you're interested, we could meet at some point during your trip.

--
Thomas Borchert (EDDH)