Cheap GPS Loggers for FAI Badges - Status?

"Tony Burton" wrote in message
...
So, say that some Garmin GPS is ICG-compliant except for the barograph
function. Could not such an FR be approved by the IGC GFAC committee
with
the restriction in its approval document that it could not be used for
height evidence?

No, since pressure altitude recording capability is a non-optional
requirement of the Technical Specification (see sections 2.4 and 2.6.5).
In any case, I believe all FAI badge-related flight performances
require altitude evidence, with the sole exception of the 5 hour
Silver/Gold duration.

Marc

Okay, then the solution to the regulatory barrier seems to be to broaden
the Tech Spec for COTS GPS units by enlarging the list of functions which
are optional. If COTS are deemed to be"a good thing" for the vastly larger
population of badge pilots vs record-seeking pilots, then the IGC/GFAC
committee ought to be finding the means to add a few "almost-compliant"
FRs to the approved list (how it can be done vs why it can't).

Of course, there's nothing in the Sporting Code that requires flight
evidence to come from one piece of equipment, otherwise we wouldn't have
cameras/baros.

Regards

--
Tony Burton

All right, how about this?

Since the barometric altitude section of approved loggers seems to be the
part that makes them so expensive, allow GPS altitude instead. Since in the
view of some the GPS altitude data is "inaccurate" then require those badge
applicants using a GPS altitude to exceed the badge altitude leg by an
amount equal to the maximum possible GPS altitude error - say 50 meters.

Bill Daniels

I don't think I've met anyone in soaring who would cheat on a badge flight.
What would the point be?

I don't know about that. I know of one pilot who was earning the C badge for
duration. He released about 500 feet higher than allowed. Then SSA Instructor
who awarded the badge said it was "close enough".

Jim Vincent
CFIG
N483SZ
illspam

On 24 May 2004 19:55:48 GMT, Don Johnstone
wrote:

Please excuse my ignorance but from what you have said
about the inaccuracy of pressure altitude recorders
is GPS altitude more accurate than pressure altitude.
On the traces that I have from my logger the two traces,
pressure and GPS are fairly consistent in their difference
at lower levels. GPS trace is QNH, baro is QFE. Is
the divergence with height a function of the inaccurate
pressure trace with an accurate GPS trace or are both
subject to inaccuracies for different reasons?


See one of the earlier posts on this thread.

Presure altitude is the difference between two pressure levels.
On a warmer than standard day the air between these levels expands so
the geometric difference is greater.

As Marc Ramsey points out the pressure altitude is lower than
geometric altitude on most soaring days.

The result is that by using pressure altitude many people who missed
out on a gold or diamond altitude gain by a small amount actually did
gain the geometric altitude.

Interestingly the hot air balloon people convert all altitude claims
to geometric altitude for record purposes.

I wonder if the FAI knows that the IGC doesn't do this?

Mike Borgelt

Mike Borgelt wrote:

The result is that by using pressure altitude many people who missed
out on a gold or diamond altitude gain by a small amount actually did
gain the geometric altitude.

Interestingly the hot air balloon people convert all altitude claims
to geometric altitude for record purposes.


How do they do this? Do they also record temperature along with pressure
altitude?

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Don Johnstone wrote in message ...
Please excuse my ignorance but from what you have said
about the inaccuracy of pressure altitude recorders
is GPS altitude more accurate than pressure altitude.
On the traces that I have from my logger the two traces,
pressure and GPS are fairly consistent in their difference
at lower levels. GPS trace is QNH, baro is QFE. Is
the divergence with height a function of the inaccurate
pressure trace with an accurate GPS trace or are both
subject to inaccuracies for different reasons?


Don,

Oh boy, bringing in QNH and QFE is bound to muddy the waters! Let's
get those out of the way: GFE is the LOCAL altimeter setting that
results in a zero altimeter setting on the runway, regardless of the
actual runway elevation. QNH is the LOCAL altimeter setting that
gives an altimeter setting on the runway that is close to the actual
runway elevation. It allows the altimeter to be used as a reference
device for altitude deconfliction, instrument approaches, etc. It
approximates MSL on the altimeter, but at higher altitudes (and
temperatures) can be off by a significant amount (which is not a
factor for ATC and mutual deconfliction issues).

GPS, on the other hand, gives an elevation above the reference sea
level. Has nothing to do with QFE or GNH. It is (on the average)a
LOT more accurate than any aircraft altimeter, if what you care about
is how high you are above MSL. Only a good radar altimeter (or laser
rangefinder) is better.

So if we were serious about altitude claims, we would require a GPS
trace, with the required altitude exceeded by a nominal amount equal
to the expected GPS error.

Which is why GPS is better for final glides, BTW.

But since everybody has an altimeter, and it doesn't need power, don't
expect it to change soon!

Kirk

Eric Greenwell wrote:
How do they do this? Do they also record temperature along with pressure
altitude?

====
Sporting Code Section 1 - Aerostats
Annex 2 - Calculation of Geometric Altitude from Barometric Altitude:

3. Meteorological information must be obtained for a position and
time as close as possible to that of the flight. The surface
pressure should be obtained together with temperature and
(optionally) humidity for a range of heights up to the height
being measured. If the meteorological information is not
available the air must be assumed dry, the temperature the
coldest possible for that location and season, and the surface
pressure the lowest that could have been possible.

4. The claimed altitude must be adjusted for the effect of the
atmospheric data by a met hod which can be shown to be correct.
Calculations have been accepted using the following methods:

1) CALCULATION OF CORRECTED ABSOLUTE ALTITUDE by Hans Akerstedt
(Version 2/95 June 1995 effective date) - a method of manual
calculation.
2) CAMERON BALLOONS PROGRAM FOR FAI RECORDS (CBFAI version 97.3
and later). This is a program which gives a result which is
as precise as the data used, calculating the atmosphere layer
by layer.
3) Direct interpolation is possible using certain types of
meteorological data. The result must usually be converted
from geopotential to geometric metres.

Altitude calculations are very complex and procedures can differ
for different types of instrument and available meteorological
data. It is recommended that specialist help be obtained.
====

I believe they still primarily use barographs (an IGC-approved flight
recorder is acceptable as a barograph). I don't think they've
transitioned over to use of GPS derived geometric altitude as of this
moment.

Marc

You laugh. In our club, all Silver distance flight must be done in a 1-26.
Seriously.

P3


"303pilot" brentUNDERSCOREsullivanATbmcDOTcom wrote in message
...
"Papa3" wrote in message
link.net...
At the end of the day, what we've done is exactly the mistake I pointed
out
in the beginning. We've allowed paranoia over a few folks who may want
to
fudge their gold distance flight or silver climb lead to a situation
that
literally requires people to stick with 1940's technology or fork over
an
extra $500 for an "approved" logger. For this cost we get what
exactly?
The satisfaction in knowing that, if a guy wants to fly his Silver
Distance
in a Nimbus IV, at least he didn't cheat? Am I the only one who sees a
certain irony in this????

LOL!!!!
You must have missed the WCG/IGC announcement that henceforth, all Silver
Distance flights are to be done in PW5s.

(running, ducking & grinning)

Brent

Right on Todd. What rarely hits the papers is that the vast majority of
major security breaches in corporate environments come not from external
hackers but from disgruntled or malicious employees. One DBA with root
access can bring on a world of hurt. Seems like we're facing a similar
situation here...


"Todd Pattist" wrote in message
news
"303pilot" brentUNDERSCOREsullivanATbmcDOTcom wrote:

I don't think I've met anyone in soaring who would cheat on a badge
flight.
What would the point be?
Badge flights are about personal accomplishment. If there is an
individual
in this sport so sad as to cheat on a badge flight, let him/her.
Record flights deserve the higher level of scrutiny because we are
comparing
performances between individuals.

I'm in favor of allowing COTS recorders in a box for
everything. They are at least as secure as the baro and
camera, and IMHO, probably as secure or more so than the IGC
approved FR. I know everyone loves the FR security, but
there are several known ways to cheat with the FR. The
entire security revolves around a secret number stored in
the box the potential cheater owns and controls, and which
is known to numerous individuals authorized by various
manufacturers. If I was going to cheat for a record, I'd
use an FR.

Regardless, if it would move the COTS proposal along by
limiting it to badge flights only, I'd support that.
Todd Pattist - "WH" Ventus C
(Remove DONTSPAMME from address to email reply.)

Kirk Stant wrote:
Oh boy, bringing in QNH and QFE is bound to muddy the waters! Let's
get those out of the way: GFE is the LOCAL altimeter setting that
results in a zero altimeter setting on the runway, regardless of the
actual runway elevation. QNH is the LOCAL altimeter setting that
gives an altimeter setting on the runway that is close to the actual
runway elevation. It allows the altimeter to be used as a reference
device for altitude deconfliction, instrument approaches, etc. It
approximates MSL on the altimeter, but at higher altitudes (and
temperatures) can be off by a significant amount (which is not a
factor for ATC and mutual deconfliction issues).

GPS, on the other hand, gives an elevation above the reference sea
level. Has nothing to do with QFE or GNH. It is (on the average)a
LOT more accurate than any aircraft altimeter, if what you care about
is how high you are above MSL. Only a good radar altimeter (or laser
rangefinder) is better.

You probably didn't mean that, since these are AGL measurements, not MSL.
--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

On Tue, 25 May 2004 02:20:28 GMT, Marc Ramsey
wrote:

Eric Greenwell wrote:
How do they do this? Do they also record temperature along with pressure
altitude?

====
Sporting Code Section 1 - Aerostats
Annex 2 - Calculation of Geometric Altitude from Barometric Altitude:

3. Meteorological information must be obtained for a position and
time as close as possible to that of the flight. The surface
pressure should be obtained together with temperature and
(optionally) humidity for a range of heights up to the height
being measured. If the meteorological information is not
available the air must be assumed dry, the temperature the
coldest possible for that location and season, and the surface
pressure the lowest that could have been possible.

4. The claimed altitude must be adjusted for the effect of the
atmospheric data by a met hod which can be shown to be correct.
Calculations have been accepted using the following methods:

1) CALCULATION OF CORRECTED ABSOLUTE ALTITUDE by Hans Akerstedt
(Version 2/95 June 1995 effective date) - a method of manual
calculation.
2) CAMERON BALLOONS PROGRAM FOR FAI RECORDS (CBFAI version 97.3
and later). This is a program which gives a result which is
as precise as the data used, calculating the atmosphere layer
by layer.
3) Direct interpolation is possible using certain types of
meteorological data. The result must usually be converted
from geopotential to geometric metres.

Altitude calculations are very complex and procedures can differ
for different types of instrument and available meteorological
data. It is recommended that specialist help be obtained.
====

I believe they still primarily use barographs (an IGC-approved flight
recorder is acceptable as a barograph). I don't think they've
transitioned over to use of GPS derived geometric altitude as of this
moment.

Marc


That's how it is done. I verified an Australian balloon altitude
record about 8 or 9 years ago. This was done according to the world
rules and they provided a nice worksheet to make it easy.

It has only been 4 years since SA was turned off but the point is that
they do reduce the data to geometric altitude. As GPS measures this
directly it would seem to be reasonable to allow GPS with suitable
allowance for GPS errors. These are far better known than the pressure
errors. Just choose the level of confidence you want.
From memory the error bands in the pressure calculation (altitude was
in excess of 30,000 feet)were quite large probably around the 99 +%
GPS error band.
Don't forget the recorder pressure calibration is done at room
temperature. There is no guarantee it is the same at -20 deg C(again
from memory, the FR low temperature limit) or even colder and in fact
outside the FR spec.

On reflection this is all too silly for words for what is really just
trivia.

Mike Borgelt