Cheap GPS Loggers for FAI Badges - Status?

At 10:18 01 June 2004, Marc Ramsey wrote: (snip)
How much security is enough?

It is perhaps here where there is the greatest problem.
It seems that most people view the 'security' measures
applied to barographs and loggers as a measure to prevent
cheating. They do not and never will. All security
does is buy time, it makes cheating more difficult
so the 'man on the Clapham Omnibus' (for those across
the pond, the ordinary man in the street) cannot easily
fake a trace. While reading this thread I am somewhat
at a loss as to why somene would want to load in a
flight to a GPS using a simulator, much easier to doctor
the ensuing computer file. Any security measure involving
a computer can be defeated, it's the time it takes
that makes the difference.
For that reason I always, if I am the OO download to
my own computer, never to anyone elses and I keep a
copy of the file forever.
A GPS sealed in a box is as secure, if not more so
than a smokey barograph. It is many more times secure
as a computer file produced by a 'secure' logger, the
security algorithums of which are historically interesting,
almost. The information contained in the GPS memory
is raw source data, that produced by the logger is
not. Replacing a proper seal as used on smokey barographs,
if all the rules are followed, is infinitely more difficult
than decoding and faking a computer file.

I seem to recall someone earlier inthis thread saying
that geometric altitude was more accurate and easily
corrected than barometric, which as we all know is
wildly inaccurate dependent on temperature which the
barograph does not record.

Papa3 wrote:

Martin,

All good points. However, I think (for example) the issue of the number of
data points is something for the market to decide. I'm sure there are
plenty of folks for whom an 11 hour trace is more than sufficient. At the
end of the day, once the standards are "reasonable" (let's not worry exactly
what that means for a moment) , market forces will dictate what is
available.


I don't agree these are good points. I did all my distance badges using a
Volkslogger for documentation, while I was using my good old Garmin 12 for
navigation, except the silver distance, for which I used a camera and a
barograph. For all these flights the old Garmin 12 would have been fairly suffcient.
It is configured with a recorded point every 30 seconds, which allows for
more than 8 hours, no flight reached this duration. As I didn't knew
how the Volkslogger detects that I passed a turn point, I checked it
on my Garmin 12, so spending at least 30 seconds in the observation
zone. I found it a very acceptable penalty. As for the overwriting
of the track log on the Garmin, this is a selectable feature, you
can also choose to stop recording when the memory is full. Anyway
I don't understand why you would want to keep several flights
recorded in the unit when trying a badge distance, if your last
flight is a success, you want to download it immediately, just in order
to verify it is really a success, otherwise, if you know it was not
a success (e.g . you didn't round some turn point), there is no
problem with overwriting this track log. And the argument about
uploaded fake track logs is defeated by the fact that each recorded
point has a time stamp, while uploaded tracks logs have their
time stamps zeroed. So I think that even the sealed box is not
necessary.

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

Don Johnstone wrote:

A GPS sealed in a box is as secure, if not more so
than a smokey barograph. It is many more times secure
as a computer file produced by a 'secure' logger, the
security algorithums of which are historically interesting,
almost. The information contained in the GPS memory
is raw source data, that produced by the logger is
not. Replacing a proper seal as used on smokey barographs,
if all the rules are followed, is infinitely more difficult
than decoding and faking a computer file.


Perhaps I am a very special person, but I think I could remove and
replace the typical lead seal on a barograph unknown to the OO, but I
don't know how to fake an IGC file from an approved flight recorder that
would pass the verification test.
--


Eric Greenwell
Washington State
USA

In article ,
says...
Eric Greenwell wrote:

Perhaps I am a very special person, but I think I could remove and
replace the typical lead seal on a barograph unknown to the OO, but I
don't know how to fake an IGC file from an approved flight recorder that
would pass the verification test.

But now that you've got the seal removed, you're not done.
You have to make a fake baro trace (something that has been
detected in the past) and a fake set of photos (something
that has also been detected before). In fact, I believe the
details of an analog baro and photo set are harder to fake
and easier to detect as fake than a bunch of digital
numbers.

I was responding to a comment that said:

"Replacing a proper seal as used on smokey barographs,
if all the rules are followed, is infinitely more difficult
than decoding and faking a computer file."

And the context was about sealing a COTS GPS in a lunch box, so I
addressed only the sealing.

I haven't thought it through carefully, but I still think I could make a
fake barogram and photos more easily than a file that could pass a IGC
verification program. Neither effort might make it past the OO.
--
-------
Eric Greenwell USA

Eric Greenwell wrote:

Perhaps I am a very special person, but I think I could remove and
replace the typical lead seal on a barograph unknown to the OO, but I
don't know how to fake an IGC file from an approved flight recorder that
would pass the verification test.

I'm sure you ARE very special Eric and you're absolutely right that a
sealed barograph is MUCH, MUCH less secure than the over-specified,
self-destructing, weakly-encrypted, kilobuck loggers the IGC mandates.

It's irrelevant to the point discussed here (fairly) consistently for
the past fortnight, however, which is that:

(1) a properly OOed COTS GPS in a lunch box is no LESS secure than a
sealed barograph and...

(2) the level of security of a sealed barograph is perfectly adequate
for the vast majority of glider flights so...

(3) Why doesn't the IGC give its imprimatur to a set of procedures which
would be internationally accepted for the vast majority of glider
flights using COTS GPS loggers right up to World champs and World records?

Since a sealed-by-an-OO barograph is accepted by the IGC as completely
adequate security for all purposes, why do we need heightened security
for GPS loggers used for those same purposes? Very few of us will ever
compete in a World Championship or set a World record. Until we do, a
COTS GPS sealed in an OOed lunchbox would be fine.

....and yes, I know YOU could unravel the seal - but then you ARE a very
special person.


Graeme Cant

"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