IGC APproval for GPS with WAAS

[Ivan Kahn]

I was wondering if any of the manufacturers are considering submitting for
IGC approval a GPS WAAS system that does not incorporate a barograph? Seems
to me that such system is far more accurate then those that incorporate a
barograph, and should also never need calibration.

Ivan

[Tim Newport-Peace]

X-no-archive: yes
In article <_1vwb.96689$Dw6.473262@attbi_s02>, Ivan Kahn
> writes
>I was wondering if any of the manufacturers are considering submitting for
>IGC approval a GPS WAAS system that does not incorporate a barograph? Seems
>to me that such system is far more accurate then those that incorporate a
>barograph, and should also never need calibration.
>
>Ivan
>
>
Most unlikely as it the Technical Specification requires a barometric
record.

While I have no intention of entering into a long discussion on why
barometric traces are required, the comparison between barometric and
GPS altitude is a useful check and in the event of GPS signal being lost
temporarily, the barometric trace will prove flight continuity.

GPS altitude cannot be used for checking for Airspace Infringements and
this would invalidate it's use in many competitions.

Tim Newport-Peace

"Indecision is the Key to Flexibility."

[Ivan Kahn]

"Tim Newport-Peace" ]> wrote in message
...
> X-no-archive: yes
> In article <_1vwb.96689$Dw6.473262@attbi_s02>, Ivan Kahn
> > writes
> >I was wondering if any of the manufacturers are considering submitting
for
> >IGC approval a GPS WAAS system that does not incorporate a barograph?
Seems
> >to me that such system is far more accurate then those that incorporate a
> >barograph, and should also never need calibration.
> >
> >Ivan
> >
> >
> Most unlikely as it the Technical Specification requires a barometric
> record.
>
> While I have no intention of entering into a long discussion on why
> barometric traces are required, the comparison between barometric and
> GPS altitude is a useful check and in the event of GPS signal being lost
> temporarily, the barometric trace will prove flight continuity.
>
> GPS altitude cannot be used for checking for Airspace Infringements and
> this would invalidate it's use in many competitions.
>
> Tim Newport-Peace
>
> "Indecision is the Key to Flexibility."

I agree, why traces are needed is really the point. But I believe a GPS with
WAAS is far more accurate than a barograph and should also be more cost
effective. But unless someone seeks approval then I would not expect any
specification to change. I was just wondering if there is any movement in
this area.

Ivan

[Tim Newport-Peace]

X-no-archive: yes
In article <hFPwb.225716$mZ5.1710772@attbi_s54>, Ivan Kahn
> writes
>I agree, why traces are needed is really the point. But I believe a GPS with
>WAAS is far more accurate than a barograph and should also be more cost
>effective. But unless someone seeks approval then I would not expect any
>specification to change. I was just wondering if there is any movement in
>this area.
>
>Ivan
>
I don't think it happens quite that way. If you submit a recorder that
does not conform the Specification in Force at the time, approval will
not be granted until it DOES conform. The specification would need to be
changed FIRST.

I do not believe that the requirement for Barometric Altitude will be
removed any time soon.

Best regards,

Tim Newport-Peace

"Indecision is the Key to Flexibility."

[Adrian Jansen]

You might want to consider the implications of WAAS. I have no direct
experience, but the principle is that you take an external signal and use it
to 'correct' the GPS location to another place - hopefully more accurate.
But what is to stop you sending bogus 'corrections' and making the GPS think
its somewhere else entirely ? The WAAS signals are much easier to generate
than the original GPS satellite signals. Sounds an easy way to cheat to me.

--
Regards,

Adrian Jansen
J & K MicroSystems
Microcomputer solutions for industrial control
"Ivan Kahn" > wrote in message
news:hFPwb.225716$mZ5.1710772@attbi_s54...
> "Tim Newport-Peace" ]> wrote in message
> ...
> > X-no-archive: yes
> > In article <_1vwb.96689$Dw6.473262@attbi_s02>, Ivan Kahn
> > > writes
> > >I was wondering if any of the manufacturers are considering submitting
> for
> > >IGC approval a GPS WAAS system that does not incorporate a barograph?
> Seems
> > >to me that such system is far more accurate then those that incorporate
a
> > >barograph, and should also never need calibration.
> > >
> > >Ivan
> > >
> > >
> > Most unlikely as it the Technical Specification requires a barometric
> > record.
> >
> > While I have no intention of entering into a long discussion on why
> > barometric traces are required, the comparison between barometric and
> > GPS altitude is a useful check and in the event of GPS signal being lost
> > temporarily, the barometric trace will prove flight continuity.
> >
> > GPS altitude cannot be used for checking for Airspace Infringements and
> > this would invalidate it's use in many competitions.
> >
> > Tim Newport-Peace
> >
> > "Indecision is the Key to Flexibility."
>
> I agree, why traces are needed is really the point. But I believe a GPS
with
> WAAS is far more accurate than a barograph and should also be more cost
> effective. But unless someone seeks approval then I would not expect any
> specification to change. I was just wondering if there is any movement in
> this area.
>
> Ivan
>
>

[Carl Buehler]

I have long been hoping the Garmin GPSmap 76S would be consided
as an IGC approved device. I usually do not enable the WAAS in my
device.
But find the 76S to be very accurate after a flight when I generate an
..igc file from the track log using GPSDump and loading it into SeeYou.
I was on a flight Sunday, in a LET-L13 in Zephyrhills, FL. I got off
tow at
3000' AGL. I had a 2.3 hr. flight. at one time during the flight I had
dropped
down to 1400' AGL, I was about to enter the pattern but found a weak
thermal and started to work it. About 50 minutes later I was at 4700'
AGL. When I landed, some club members told me they thought that
probably would have been good for a Silver Altitude. I am not sure.
That was like my 20 TH solo flight.

If The Garmins would be an IGC approved device. I would carry my 76S
on every
flight. You never know!

Carl


"Ivan Kahn" > wrote in message news:<hFPwb.225716$mZ5.1710772@attbi_s54>...
> "Tim Newport-Peace" ]> wrote in message
> ...
> > X-no-archive: yes
> > In article <_1vwb.96689$Dw6.473262@attbi_s02>, Ivan Kahn
> > > writes
> > >I was wondering if any of the manufacturers are considering submitting
> for
> > >IGC approval a GPS WAAS system that does not incorporate a barograph?
> Seems
> > >to me that such system is far more accurate then those that incorporate a
> > >barograph, and should also never need calibration.
> > >
> > >Ivan
> > >
> > >
> > Most unlikely as it the Technical Specification requires a barometric
> > record.
> >
> > While I have no intention of entering into a long discussion on why
> > barometric traces are required, the comparison between barometric and
> > GPS altitude is a useful check and in the event of GPS signal being lost
> > temporarily, the barometric trace will prove flight continuity.
> >
> > GPS altitude cannot be used for checking for Airspace Infringements and
> > this would invalidate it's use in many competitions.
> >
> > Tim Newport-Peace
> >
> > "Indecision is the Key to Flexibility."
>
> I agree, why traces are needed is really the point. But I believe a GPS with
> WAAS is far more accurate than a barograph and should also be more cost
> effective. But unless someone seeks approval then I would not expect any
> specification to change. I was just wondering if there is any movement in
> this area.
>
> Ivan

[Eric Greenwell]

Carl Buehler wrote:

> If The Garmins would be an IGC approved device. I would carry my 76S
> on every
> flight. You never know!

When you start flying cross-country, you'll be carrying it anyway!

--
-----
Replace "SPAM" with "charter" to email me directly

Eric Greenwell
Washington State
USA

[Bruce Hoult]

In article >,
"Adrian Jansen" > wrote:

> You might want to consider the implications of WAAS. I have no direct
> experience, but the principle is that you take an external signal and use it
> to 'correct' the GPS location to another place - hopefully more accurate.
> But what is to stop you sending bogus 'corrections' and making the GPS think
> its somewhere else entirely ? The WAAS signals are much easier to generate
> than the original GPS satellite signals. Sounds an easy way to cheat to me.

But how far can the WAAS signal "correct" the GPS one?

I assume the principle is that the transmitter knows exactly where it
really is, so if GPS says it is somewhere else then the difference is an
error which will apply to all other GPS receivers in the area. Since
the GPS error is likely to be on the order of 5m - 10m, and very very
unlikely to be more than a couple of hundred meters, I would expect the
system to be designed to correct the GPS positions by no more than a few
hundred meters.

Another characteristic is that the correction is the same not only for a
reasonably large geographic area, but that the necessary correction
changes quite slowly, over a period of many minutes. If I was designing
the system, I expect I would also take advantage of that to reduce the
amount of information that need to be transmitted.

So I would expect a maximum correction possible of, say, less than a km,
and rapid changes to the correction to be either impossible or else
rather unusual and therefore suspicious.

I don't see how you could use that to make any significant difference to
a glider flight.

-- Bruce

[Ivan Kahn]

"Adrian Jansen" > wrote in message
...
> You might want to consider the implications of WAAS. I have no direct
> experience, but the principle is that you take an external signal and use
it
> to 'correct' the GPS location to another place - hopefully more accurate.
> But what is to stop you sending bogus 'corrections' and making the GPS
think
> its somewhere else entirely ? The WAAS signals are much easier to
generate
> than the original GPS satellite signals. Sounds an easy way to cheat to
me.
>
> --
> Regards,

I do not believe it is at all easy to fake GPS WAAS and GPS is already
acceptable for position. But it is very easy to fake a barograph.

Ivan

[Ian Strachan]

In article >, Ivan Kahn
> writes

snip

>I do not believe it is at all easy to fake GPS WAAS and GPS is already
>acceptable for position.

>But it is very easy to fake a barograph.

A drum-type baro, yes, it has unfortunately been done and some cases
have been publicised in the public domain. Not easy if it is an
electronic pressure sensor embedded in a secure GNSS flight recorder.
You have to fake both the pressure and GNSS-altitude traces and make
them similar. Now that is less that straightforward, I think.

Yes, you could probably fake one, or the other. But both together is
not easy. How many people have access to a GPS simulator and a pressure
chamber? And the ability to co-ordinate the two into a plausible IGC
flight data file that still passes the security checks?

Also, the faked fixes would have to agree with the weather of the day,
thermal/wave conditions, winds with height, etc. All of which can be
checked against other flights done on that date and in the same area.

Finally, on flights to be validated an OO has to observe the recorder in
the glider and the time and place of takeoff and landing. How do you
fake this beforehand?

Yes, I suppose that anything is possible but I suggest that the "height
of the fence" that IGC has put up against cheating or malpractice with
GNSS flight recorders, is suitably high. Make it too high and we would
not fly because there would be too many checks to do first!

--
Ian Strachan

[Mike Borgelt]

On Tue, 25 Nov 2003 22:37:33 +0000, Tim Newport-Peace
]> wrote:


>I don't think it happens quite that way. If you submit a recorder that
>does not conform the Specification in Force at the time, approval will
>not be granted until it DOES conform. The specification would need to be
>changed FIRST.

As opposed to NOT approving a recorder which does meet the
specification at the time and then changing the specification later?
Which GFAC has done.
>
>I do not believe that the requirement for Barometric Altitude will be
>removed any time soon.

I agree, that would be far too sensible a decision for IGC/GFAC to
make.

Mike Borgelt

[Adrian Jansen]

I agree with your analysis in principle, but I dont *know* that WAAS works
like this. In any case I dont see any point in the enhanced accuracy of WAAS
for glider flights. The errors in the normal GPS signals are already small
enough. I just dont want to see an 'improvement' leading to yet another
unforseen problem.

--
Regards,

Adrian Jansen
J & K MicroSystems
Microcomputer solutions for industrial control
"Bruce Hoult" > wrote in message
...
> In article >,
> "Adrian Jansen" > wrote:
>
> > You might want to consider the implications of WAAS. I have no direct
> > experience, but the principle is that you take an external signal and
use it
> > to 'correct' the GPS location to another place - hopefully more
accurate.
> > But what is to stop you sending bogus 'corrections' and making the GPS
think
> > its somewhere else entirely ? The WAAS signals are much easier to
generate
> > than the original GPS satellite signals. Sounds an easy way to cheat to
me.
>
> But how far can the WAAS signal "correct" the GPS one?
>
> I assume the principle is that the transmitter knows exactly where it
> really is, so if GPS says it is somewhere else then the difference is an
> error which will apply to all other GPS receivers in the area. Since
> the GPS error is likely to be on the order of 5m - 10m, and very very
> unlikely to be more than a couple of hundred meters, I would expect the
> system to be designed to correct the GPS positions by no more than a few
> hundred meters.
>
> Another characteristic is that the correction is the same not only for a
> reasonably large geographic area, but that the necessary correction
> changes quite slowly, over a period of many minutes. If I was designing
> the system, I expect I would also take advantage of that to reduce the
> amount of information that need to be transmitted.
>
> So I would expect a maximum correction possible of, say, less than a km,
> and rapid changes to the correction to be either impossible or else
> rather unusual and therefore suspicious.
>
> I don't see how you could use that to make any significant difference to
> a glider flight.
>
> -- Bruce