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)
** 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.
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
<Sam> writes:>> Record the pressure readings for the whole flight and you eliminate this
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.)
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
Check the model rocketry pages. There are a number of lightweight altitude
tracking devices out there.ask the question at rec.models.rockets
<Altimeter> wrote in message> What would be the cost effective but accurate way of reading flight height
On Sun, 25 Apr 2004 18:11:30 +1000, <Altimeter> wrote:
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
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