Cheap GPS Loggers for FAI Badges - Status?

Janos Bauer wrote:
Marc Ramsey wrote:
It has nothing to do with competence. I agree with some of your
opinions, others do not.

I mean, you usually aware of the technical background (security, GPS
issues, etc-etc). On the other hand you often refuse certain suggestions
referring to existing rules and not to technical problems.

So, I must not be truly competent 8^)

Tradition is a big factor. The perceived (but not adequately studied,
in my opinion) inaccuracy of GPS altitude is another.

I also haven't really studied it but last Sunday it was the second time
when I had to fly xc without variometer and I was happy with the simple
GPS (no WAAS etc.) based palm&soaringpilot combo. I think it would be
impossible if there was really huge error (bigger than on those 20 year
old barographs).

You are comparing apples to oranges. GPS measures geometric altitude
with a typical error of, say, +/- 50 feet. Barographs measure
calibrated pressure altitude with a typical error of, say, +/- 50 feet.
GPS altitude can not be corrected to pressure altitude with reasonable
error bounds, unless specific meteorological data is provided for the
time and place of the flight. Pressure altitude can not be corrected to
geometric altitude with reasonable error bounds, unless specific
meteorological data is provided for the time and place of the flight.
Without making these meteorological corrections, geometric and
calibrated pressure altitude can differ by as much as 1000 feet for a
Diamond altitude gain.

It doesn't matter how they are treated, as long as they can be
successfully calibrated within the set interval. The corrected
pressure altitudes taken from a barogram may be off by a hundred feet
or so, but they still provide a more accurate measurement of the
precise form of altitude required by the current IGC rules, than any
COTS GPS.


I don't think they are calibrated for all the temperatures.

There is no requirement that barographs be corrected for temperature.

I don't think all the mechanical impacts can be handled by calibration
(I myself (saw others do it few times) locked out the needle of one
old smoky barograph and we had to bent it back to working position,
how do you handle such an "impact"?)

That barograph should have been marked as potentially faulty. An OO, if
aware of this, should refuse to certify a flight using it until it is
repaired and recalibrated.

And the most important issue, what I stated
befo neither barographs nor cameras are sealed by OO on most of the
places I visited...

The Sporting Code requires sealing the barograph, but not necessarily
the cameras (SC3 4.6.3, 4.7.2). If an OO is unable to follow these
simple rules, how likely is it that he/she will follow the more
technically complex procedures that might be required for a COTS GPS?

No one wants to cheat with them, it's just the way things going on some
(maybe most) places.

I've seen similar things. Given this, the obvious solution would be to
award badges using the honor system. If this is not acceptable, then
some level of procedural and/or technical security measures must be in
the rules (even if some do not follow them). How much security is enough?

Marc

Marc Ramsey wrote:

You are comparing apples to oranges. GPS measures geometric altitude
with a typical error of, say, +/- 50 feet. Barographs measure
calibrated pressure altitude with a typical error of, say, +/- 50 feet.
GPS altitude can not be corrected to pressure altitude with reasonable
error bounds, unless specific meteorological data is provided for the
time and place of the flight. Pressure altitude can not be corrected to
geometric altitude with reasonable error bounds, unless specific
meteorological data is provided for the time and place of the flight.
Without making these meteorological corrections, geometric and
calibrated pressure altitude can differ by as much as 1000 feet for a
Diamond altitude gain.

The whole altitude task is about the ability to gain certain amount of
energy from air (thermal, wave, something else). For me it's a geometric
issue. If someone is able to get from A to B and the altitude difference
is more than X than it's fine. Not the air pressure at that altitude
qualifies the pilot.
You already agree with it so what do we argue about?

I don't think they are calibrated for all the temperatures.
There is no requirement that barographs be corrected for temperature.

Hmm, those thin metal plates and other small parts could behave quite
differently at +40C than -40C (typical wave temperature at my country).

That barograph should have been marked as potentially faulty. An OO, if
aware of this, should refuse to certify a flight using it until it is
repaired and recalibrated.

Should.

And the most important issue, what I stated
befo neither barographs nor cameras are sealed by OO on most of the
places I visited...


The Sporting Code requires sealing the barograph, but not necessarily
the cameras (SC3 4.6.3, 4.7.2). If an OO is unable to follow these
simple rules, how likely is it that he/she will follow the more
technically complex procedures that might be required for a COTS GPS?

No they won't.

No one wants to cheat with them, it's just the way things going on
some (maybe most) places.


I've seen similar things. Given this, the obvious solution would be to
award badges using the honor system. If this is not acceptable, then
some level of procedural and/or technical security measures must be in
the rules (even if some do not follow them). How much security is enough?

I would accept any trace file and a sign from the OO. Yes, from the
same OO who doesn't seal the barograph. It's the same level of security
as the current barograph+photo process.

/Janos

I've found it a little funny that there's all this fuss about
the measuring devices, yet I've read in several articles about
silver badge flights and radio chatter and finding
thermals despite:

SC 3, 2.1.1 a

"The Silver distance flight should be flown without navigational
or other assistance given over the radio (other than permission
to land on an airfield) or help or guidance from other aircraft."

This sport has elements of the honor system in it already, there
are already some who do cheat (most often inadvertently), but
I for one think that the sport is so small that the overemphasis
on security discourages participation to a much greater degree
than any cheating under a COTS gps approval for badges would
detract or discourage.

No one wants to cheat with them, it's just the way things going on
some (maybe most) places.

I've seen similar things. Given this, the obvious solution would be to
award badges using the honor system. If this is not acceptable, then
some level of procedural and/or technical security measures must be in
the rules (even if some do not follow them). How much security is enough?
--

------------+
Mark Boyd
Avenal, California, USA

Hi

Without making these meteorological corrections, geometric and
calibrated pressure altitude can differ by as much as 1000 feet for a
Diamond altitude gain.

Marc

I do not know about the conversion process required to convert geometric and
I assume the actual within the bounds of GPS error altitude, to pressure
altitude. However given the assertion that the pressure altitude can differ
by as much as 1000ft from the geometric altitude, does it imply that two
pressure altitudes can actually differ by 2000ft? Would it not provide
sufficient argument to switch to geometric altitude?

Paul

Paul Bart wrote:
I do not know about the conversion process required to convert geometric and
I assume the actual within the bounds of GPS error altitude, to pressure
altitude. However given the assertion that the pressure altitude can differ
by as much as 1000ft from the geometric altitude, does it imply that two
pressure altitudes can actually differ by 2000ft? Would it not provide
sufficient argument to switch to geometric altitude?

Yes, this is correct. You don't have to climb as high on a cold winter
day, as you would on a hot summer day, to obtain a specific pressure
altitude gain. But, I suspect some (maybe most?) would say that we have
always measured pressure altitude is this sport, and that we should
continue doing so...

Marc

"Marc Ramsey" wrote in message
. com...
Paul Bart wrote:
However given the assertion that the pressure altitude can differ
by as much as 1000ft from the geometric altitude, does it imply that two
pressure altitudes can actually differ by 2000ft? Would it not provide
sufficient argument to switch to geometric altitude?

Yes, this is correct. You don't have to climb as high on a cold winter
day, as you would on a hot summer day, to obtain a specific pressure
altitude gain. But, I suspect some (maybe most?) would say that we have
always measured pressure altitude is this sport, and that we should
continue doing so...

Marc

Hi Marc

Thanks for your reply. Given the budding status of my gliding career, this
is not likely to be an issue for me any time soon , however given that GPS
can *potentially* reduce an error, by up to 1000 ft it should be seriously
considered. I wonder if the resistance to change is mainly due to the high
average age of the gliding fraternity?

Paul

On Thu, 03 Jun 2004 13:52:29 GMT, "Paul Bart"
wrote:


"Marc Ramsey" wrote in message
.com...
Paul Bart wrote:
However given the assertion that the pressure altitude can differ
by as much as 1000ft from the geometric altitude, does it imply that two
pressure altitudes can actually differ by 2000ft? Would it not provide
sufficient argument to switch to geometric altitude?

Yes, this is correct. You don't have to climb as high on a cold winter
day, as you would on a hot summer day, to obtain a specific pressure
altitude gain. But, I suspect some (maybe most?) would say that we have
always measured pressure altitude is this sport, and that we should
continue doing so...

Marc

Hi Marc

Thanks for your reply. Given the budding status of my gliding career, this
is not likely to be an issue for me any time soon , however given that GPS
can *potentially* reduce an error, by up to 1000 ft it should be seriously
considered. I wonder if the resistance to change is mainly due to the high
average age of the gliding fraternity?


I have a strong suspicion that climbing to a pressure altitude should
present much the same difficulty regardless of which way it differs
from the geometric altitude, but climbing to a geometric altitude will
get easier as the pressure (and hence pressure altitude) rises.

Unless I'm much mistaken, this could be used as an argument for
retaining the pressure altitude for badges.

What have I missed or misunderstood here?

--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

Paul Bart wrote:
"Marc Ramsey" wrote in message
Yes, this is correct. You don't have to climb as high on a cold winter
day, as you would on a hot summer day, to obtain a specific pressure
altitude gain. But, I suspect some (maybe most?) would say that we have
always measured pressure altitude is this sport, and that we should
continue doing so...

Thanks for your reply. Given the budding status of my gliding career, this
is not likely to be an issue for me any time soon , however given that GPS
can *potentially* reduce an error, by up to 1000 ft it should be seriously
considered.

But, using GPS altitude only reduces the error if we were measuring
geometric altitude. Using GPS altitude under the present rules would
*increase* the error, because we are presently measuring pressure altitude.

I wonder if the resistance to change is mainly due to the high
average age of the gliding fraternity?

I'm not going to touch that one...

Marc

"Paul Bart" wrote in message news:x2Gvc.4102

however given that GPS
can *potentially* reduce an error, by up to 1000 ft it should be seriously
considered. I wonder if the resistance to change is mainly due to the high
average age of the gliding fraternity?

Paul


You seem to have missed the frequently stated point that the
difference is not an error. An error free measurement of pressure
altitude will not be equal to an error free gps (geometric) altitude
except under rare conditions.

Recognition of this fact may have something to do with age, but the
real issues are recognizing what is to be measured, why it is being
measured, and then determining whether it is reasonable to change to
measuring something else.


Andy

"Andy Durbin" wrote in message
om...
"Paul Bart" wrote in message news:x2Gvc.4102

however given that GPS
can *potentially* reduce an error, by up to 1000 ft it should be
seriously
considered. I wonder if the resistance to change is mainly due to the
high
average age of the gliding fraternity?

Paul


You seem to have missed the frequently stated point that the
difference is not an error. An error free measurement of pressure
altitude will not be equal to an error free gps (geometric) altitude
except under rare conditions.

No I did not. You are correct, I have incorrectly used the word error if
one considers it's meaning in a relation to the output of the measuring
device, however that was not my intention.


Recognition of this fact may have something to do with age, but the
real issues are recognizing what is to be measured,



Height above ground I would have thought. If I understand the preceding
discussion correctly, pressure altitude was used because there were no other
viable options, not because it was a good measure of height above ground.



why it is being measured,



To either establish benchmark, or to fulfill some requirements. For each of
these I would rather know the actual distance above ground, not a measure
that depends on prevailing meteorological conditions. Unless, of course,
you consider Martin's observation, that the effort to climb to a particular
pressure altitude takes about the same effort regardless of the geometric
altitude and also assuming that it is the effort that is important, rather
then the actual height above ground.



and then determining whether it is reasonable to change to
measuring something else.





Thank you for your observation.



Paul