At 07:11 AM 18/02/06, you wrote:
As for the GPS versus pressure altitude, the physics of how they do this is
proprietary at this stage but the hardware chosen from day one is probably
the best transducer for the job. I know of 3 companies using them, they have
an onboard temp sensor, their drift over time is excellent and they have a
10 bit ADC onboard. As I have said the details of how they achieve this is
not relevant so long as it works. The team at FLARM are a group of dedicated
engineers with extensive software background and a full knowledge of DSP
techniques and modern software tools such as MATLAB at their disposal - I
think they are quite qualified at sorting out the Baro aiding issues , just
to keep Mike happy. Also FYI one of the FLARM engineers also works for a
sensor company - developing sensors!
All of which does ZERO about the problem of the static pressure
source. A position error of 5 knots at 100KIAS amounts to a static
pressure error of around 50 feet.There are plenty of gliders with
position errors of this magnitude. That is for a proper static source
not for cockpit static randomised by the nose vent, window vent,
exhaust exits canopy leaks etc
Is the sensor the Intersema 5534A or B? If not, what are the specs
for resolution, accuracy, drift with aging, drift with temperature,
of the pressure sensor used? Even if they are close to zero you are
still stuck with the static source error which seems to me to be to
be at least as large as the difference in reading between two nearly
co-located GPS units of the same type running the same firmware in an
excellent sky exposure.
Don't get me wrong I'm a supporter of the low cost, electronically
enhanced, see and avoid concept not only for gliding but I've pushed
the idea over the the late lamented AUFCHAT group.
Mike
Borgelt Instruments - manufacturers of quality soaring instruments
phone Int'l + 61 746 355784
fax Int'l + 61 746 358796
cellphone Int'l + 61 428 355784
Int'l + 61 429 355784
email: [EMAIL PROTECTED]
website: www.borgeltinstruments.com
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