Altitude, flight height reading

What would be the cost effective but accurate way of reading flight height
(altitude) of model aircraft and how this reading would relate the local
QNH

 

[Rob McKenzie]

Depends on the weight you can take. If you can take 120gms easiest way is a
Garmin Geko 201 +-50mtrs but generally around +-25mtrs, or a Garmin Geko 301
+- 3 mtrs with proper calibration.

--

<Altimeter> wrote in message
news:408b72bb$0$16964$afc38c87@news.optusnet.com.au...

What would be the cost effective but accurate way of reading flight height
(altitude) of model aircraft and how this reading would relate the local
QNH

 

[Art]

Be advised, using a barometric device, you will need to "calibrate" it to
local barometric pressure each time you attempt to make use of it. Otherwise
the reading will be incorrect.<

The GPS devices that is being referred to would be preferable since they
use the satellite datum to do the references.
Depending on the payload capabilities of your specific airframe, loading
characteristics, etc that you can operate within. The device obviously
will either need to record the information internally, or be capable of
communicating the information to your recording devices at the control
site. This will also contribute to the actual devices that you result in
actually using.
You may want to check out some of the search engines specifically in

regards to model aircraft design, use, and operations. Cheers
"Rob McKenzie" <x@x.com> wrote in message
news:qUKic.9296$qq6.7091@news-server.bigpond.net.au...

Depends on the weight you can take. If you can take 120gms easiest way is
a
Garmin Geko 201 +-50mtrs but generally around +-25mtrs, or a Garmin Geko
301
+- 3 mtrs with proper calibration.

--

Altimeter> wrote in message
news:408b72bb$0$16964$afc38c87@news.optusnet.com.au...
What would be the cost effective but accurate way of reading flight
height
(altitude) of model aircraft and how this reading would relate the local
QNH

 

[Kyler Laird]

"Art" <stubby@comcast.net> writes:

Be advised, using a barometric device, you will need to "calibrate" it to
local barometric pressure each time you attempt to make use of it.

Record the pressure readings for the whole flight and you eliminate this
need. Then you have even less work than with GPS to calculate the max.
height AGL (within a similar degree of accuracy).

--kyler

 

[Michael Mackay-Blair]

Check the model rocketry pages. There are a number of lightweight altitude
tracking devices out there.ask the question at rec.models.rockets

MMB
<Altimeter> wrote in message
news:408b72bb$0$16964$afc38c87@news.optusnet.com.au...

What would be the cost effective but accurate way of reading flight height
(altitude) of model aircraft and how this reading would relate the local
QNH

 

This is not an option because I'm planning to build an autopilot to control
the airplane for level flight which means that I need to measure the
attitude in realtime an measure accurately.

Record the pressure readings for the whole flight and you eliminate this
need. Then you have even less work than with GPS to calculate the max.
height AGL (within a similar degree of accuracy).

--kyler

 

[MC]

Sam wrote:

This is not an option because I'm planning to build an autopilot to control
the airplane for level flight which means that I need to measure the
attitude in realtime an measure accurately.

Record the pressure readings for the whole flight and you eliminate this
need. Then you have even less work than with GPS to calculate the max.
height AGL (within a similar degree of accuracy).

ahh.., then you'll need to use an absolute pressure sensor.
uhmmmm. how much payload can your model carry ?
(I mean, you'll need a battery, some sensors, possibly a radio link,
a microprocessor and some actuators)

 

[Kyler Laird]

<Sam> writes:

Record the pressure readings for the whole flight and you eliminate this
need. Then you have even less work than with GPS to calculate the max.
height AGL (within a similar degree of accuracy).

This is not an option because I'm planning to build an autopilot to control
the airplane for level flight

There's no need to calibrate it at all it if you just want to maintain level
flight. This is common with autopilots on larger planes. You don't need to
use an altimeter setting unless you have an altitude preselect.

(If something on the ground needs to communicate in terms of absolute
altitude, make it do the conversion. That's how our transponders work.)

which means that I need to measure the
attitude in realtime an measure accurately.

I'm not parsing this.

--kyler

 

[David L. Jones]

"Rob McKenzie" <x@x.com> wrote in message news:<qUKic.9296$qq6.7091@news-server.bigpond.net.au>...

Depends on the weight you can take. If you can take 120gms easiest way is a
Garmin Geko 201 +-50mtrs but generally around +-25mtrs, or a Garmin Geko 301
+- 3 mtrs with proper calibration.

Only problem is the Gecko won't log the altitude for you.
The easiest solution if you wanted a complete log is to use a GPSr
which logs altitude as well. Then you'd have a complete self contained
log of location and height which you can read back into your PC. No
programming or design involved.
If however you want to send the height info back via telemetry then a
bare GPS module may be a better choice, as you'd have to interface to
some sort of micro anyway.
You can lower the weight of the GPS by using smaller batteries, as you
wouldn't need 10-20 hours of operation that a regular GPSr would give
you.

Regards
Dave

 

[Phil Allison]

"MC" <MC@nonexistant.place>

ahh.., then you'll need to use an absolute pressure sensor.

** Not just any old pressure sensor, but one that responds to the
infinitesimal changes so the model will fly level at heights of only a few
tens of metres above the ground.

What he actually needs is a ground tracking radar system - like F111s
use to fly low and fast.





............. Phil

 

On Sun, 25 Apr 2004 18:11:30 +1000, <Altimeter> wrote:

What would be the cost effective but accurate way of reading flight height
(altitude) of model aircraft and how this reading would relate the local
QNH

The February 2001 isue of Circuit Cellar had an article about a low
cost and low power altimeter project. It won second place in their
Design2K contest.

http://www.circuitcellar.com/design2k/winners/third.htm#ea

Regards
David

----
reply to

dmmilne at ozemail dot com dot au

 

[Shawn Brown]

A radar altimeter will give height above the ground, but terrain avoidance
radar will give you forward looking terrain info. Depending on how big the
model is, and how much weight it can lift, you could use a radar altimeter
from a GA aircraft. You'll need map of the earth if you want to hug the
terrain. I believe the Tomahawk cruise missile uses a GPS and digital
terrain map of its route, and some sort of sensor for double checking the
course based on the digital map, but I'm not 100% positive. I don't think
it's the same exact technology that is in the F111. Clearly it works
though!

--
Shawn

"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:408cc997$0$4544$afc38c87@news.optusnet.com.au...

"MC" <MC@nonexistant.place

ahh.., then you'll need to use an absolute pressure sensor.



** Not just any old pressure sensor, but one that responds to the
infinitesimal changes so the model will fly level at heights of only a few
tens of metres above the ground.

What he actually needs is a ground tracking radar system - like F111s
use to fly low and fast.





............ Phil