GPS as an altimeter?

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Zathras of the Great Machine - 06 Mar 2004 20:15 GMT

Yep, another weird question about another idea a friend came up with.
Could the GPS system be used to determine the apogee of a rocket? In
theory is sounds plausable, such as if someone was attempting a very
high altitude flight beyond where normal barometric units would cease
working. Just curious.

Chuck

Reply to this Message

Gary - 06 Mar 2004 20:45 GMT

> Yep, another weird question about another idea a friend came up with.
> Could the GPS system be used to determine the apogee of a rocket? In
[quoted text clipped - 3 lines]
>
> Chuck

No problem.

I have flown a portable e-trex GPS receiver which can be set to
automatically record a track, including altitude, several times.

Lock is sensitive to the motion of the unit (antenna) and it typically
loses lock on boost, but (usually) recovers "around" apogee. Probably
not accurate enough for detailed altitude studies, but it gives a neat
"global" track of the flight. I'm actually working on a dedicated model
to fly this thing with more recovery stabilization in the payload section.

I'm sure there are multi-channel models available with higher fix update
rates and better antennas than the little Garmin, but its what I have to
play with right now.

Signature

Gary Bolles
NAR 82636

summum jus, summa injuria est

To contact me; bollesg at comcast dot net
http://home.comcast.net/~bollesg/rockets/rockets.html

Reply to this Message

David - 07 Mar 2004 00:26 GMT

I've launched my GPS in my rocket a couple of times. The GPS altitude is
not nearly as accurate as the longitude and latitude accuracy. It does give
you a good idea within a few hundred feet, though. I believe that most
consumer GPS units are limited to 60,000 feet. Another dissapointing aspect
of my particular Garmin GPS is that the max and average speed only take into
account x/y movement, not z movement, so the average speed was only reported
as 16 MPH, even though it went up 2000 feet in a few seconds.

Exactly how high do you have to go before barometric units don't work? I
think it's higher than 60,000 feet.

-- David

> Yep, another weird question about another idea a friend came up with.
> Could the GPS system be used to determine the apogee of a rocket? In
[quoted text clipped - 3 lines]
>
> Chuck

Reply to this Message

Zathras of the Great Machine - 07 Mar 2004 15:41 GMT

I keep telling folks that there isn't an idea they can come up with
that someone isn't already trying, this is case in point I think. And
there's always someone wanting to push the envelope too, so a very high
altitude system would be needed for that. The project that got me back
into rocketry falls in that catagory...along with my big mouth to
mention it to someone else and them saying "ok, let's try it". After I
win a lottery somewhere it'll be a snap to do too ;-) But that's quite a
ways down the road, right now the learning curve is being alot of fun in
itself, such as when an idea like this pops up that I hadn't considered
personally. That's what I get for not being up on the latest tech toy
fashions I suppose.

>Exactly how high do you have to go before barometric units don't work? I think it's higher than 60,000 feet.
>
>-- David

That sounds right from what little I know since the highest reading
commercial altimeter I've heard of goes to 50,000 feet. Certainly plenty
for most normal situations, if there is such a thing :-)

Chuck

Reply to this Message

Mfreptiles - 07 Mar 2004 23:16 GMT

>Exactly how high do you have to go before barometric units don't work? I
>think it's higher than 60,000 feet.

Use an accelerometer based altimeter instead. For GPS tracking try
http://gpsflight.com

Mike Fisher

Reply to this Message

Model Forum / General / Rockets / March 2004

GPS as an altimeter?