Position Recorders, Accuracy, and Badge altitude gains

Leah and I are down here at Chilhowee for a VSA rally and had an enjoyable flight in the Ka7 today attempting a silver altitude gain for the highly sought after VSA Silver Coin. Unfortunately by the time we were hot, tired, hungry, in pain, and had to pee we hadn't quite made the gain. I found the trace for my FlywithCE interesting though. We released about 2400 MSL and I soon remembered that I hadn't turned on the FlywithCE. So I turned it on at about 3000 I think. Check out the trace: http://www.onlinecontest.org/olc-2.0...l?dsId=2421969

It seems that the FlywithCE was trying to insist that I had started on the ground, then realized that wasn't right, and attempted to correct for it by jumping the altitude up about 3000 feet. If it had just recorded the actual altitude it would've been fine. I would've had a trace starting in mid-air, right where I turned on the recorder.

The IGC decided that position recorders like the FlywithCE will be allowed for Silver and Gold altitude gain after this fall. Would I be able to claim this obviously bogus trace for Silver Altitude? (evil grin). I suspect this is a problem associated with not turning the thing on until mid flight but dang shouldn't it just record what the actual position is???

On May 27, 1:44*pm, Tony wrote:
Leah and I are down here at Chilhowee for a VSA rally and had an enjoyable flight in the Ka7 today attempting a silver altitude gain for the highly sought after VSA Silver Coin. *Unfortunately by the time we were hot, tired, hungry, in pain, and had to pee we hadn't quite made the gain. *I found the trace for my FlywithCE interesting though. *We released about 2400 MSL and I soon remembered that I hadn't turned on the FlywithCE. *So I turned it on at about 3000 I think. *Check out the trace:http://www.onlinecontest.org/olc-2.0....html?dsId=242...

It seems that the FlywithCE was trying to insist that I had started on the ground, then realized that wasn't right, and attempted to correct for it by jumping the altitude up about 3000 feet. *If it had just recorded the actual altitude it would've been fine. *I would've had a trace starting in mid-air, right where I turned on the recorder.

The IGC decided that position recorders like the FlywithCE will be allowed for Silver and Gold altitude gain after this fall. *Would I be able to claim this obviously bogus trace for Silver Altitude? (evil grin). *I suspect this is a problem associated with not turning the thing on until mid flight but dang shouldn't it just record what the actual position is???

When you first turn on a GPS receiver, it takes somewhere between a
few seconds and minutes for it to figure out where it is and find
sufficient satellites to track for a full 3D fix. During that period,
a flight or position recorder should set the navigation warning flag
in the recorded fixes, indicating the full 3D navigation is not
available. I can't download the IGC file (as I'm not registered on
the OLC site), but I suspect you'll find that the first few B records
have the character "V" in column 24, indicating no GPS data or 2D
fix. In any case, if you submitted such an IGC file to the "Badge
Guy" after October 1, it would be rejected due to lack of an
acceptable altitude baseline prior to takeoff...

Marc

On Sunday, May 27, 2012 1:44:25 PM UTC-7, Tony wrote:
Leah and I are down here at Chilhowee for a VSA rally and had an enjoyable flight in the Ka7 today attempting a silver altitude gain for the highly sought after VSA Silver Coin. Unfortunately by the time we were hot, tired, hungry, in pain, and had to pee we hadn't quite made the gain. I found the trace for my FlywithCE interesting though. We released about 2400 MSL and I soon remembered that I hadn't turned on the FlywithCE. So I turned it on at about 3000 I think. Check out the trace: http://www.onlinecontest.org/olc-2.0...l?dsId=2421969

It seems that the FlywithCE was trying to insist that I had started on the ground, then realized that wasn't right, and attempted to correct for it by jumping the altitude up about 3000 feet. If it had just recorded the actual altitude it would've been fine. I would've had a trace starting in mid-air, right where I turned on the recorder.

The IGC decided that position recorders like the FlywithCE will be allowed for Silver and Gold altitude gain after this fall. Would I be able to claim this obviously bogus trace for Silver Altitude? (evil grin). I suspect this is a problem associated with not turning the thing on until mid flight but dang shouldn't it just record what the actual position is???

That seems concerning, hopefully folks from FlywithCE, and SSA and IGC will look at this. There is nothing in the IGC file that seems to explain this.. Its just recording apparently normal 3D fixes. Does the IGC file direct from the device/logbook program have anything unusual looking in it?

Darryl

Darryl

On Sunday, May 27, 2012 1:44:25 PM UTC-7, Tony wrote:
Leah and I are down here at Chilhowee for a VSA rally and had an enjoyable flight in the Ka7 today attempting a silver altitude gain for the highly sought after VSA Silver Coin. Unfortunately by the time we were hot, tired, hungry, in pain, and had to pee we hadn't quite made the gain. I found the trace for my FlywithCE interesting though. We released about 2400 MSL and I soon remembered that I hadn't turned on the FlywithCE. So I turned it on at about 3000 I think. Check out the trace: http://www.onlinecontest.org/olc-2.0...l?dsId=2421969

It seems that the FlywithCE was trying to insist that I had started on the ground, then realized that wasn't right, and attempted to correct for it by jumping the altitude up about 3000 feet. If it had just recorded the actual altitude it would've been fine. I would've had a trace starting in mid-air, right where I turned on the recorder.

The IGC decided that position recorders like the FlywithCE will be allowed for Silver and Gold altitude gain after this fall. Would I be able to claim this obviously bogus trace for Silver Altitude? (evil grin). I suspect this is a problem associated with not turning the thing on until mid flight but dang shouldn't it just record what the actual position is???

That seems concerning, hopefully folks from FlywithCE, and SSA and IGC will look at this. There is nothing in the IGC file that seems to explain this (Marc - no 2D fix flags I can see). Its just recording apparently normal 3D fixes. Does the IGC file direct from the device/logbook program have anything unusual looking in it?

What is also interesting is my reading of current FAI rules is there is no clear language/simple requirement for the OO and/or pilot to ensure the flight recorder/logger is actually turned on before flight. The OO required to do things like ensure the device is in the glider, attached, not tamperable (I don't read turning on as tampering) and to independently verify the take off an departure time - but so what if the OO knows the take off time, it the recorder was not turned on. Sure you expect the OO to do their job here and note the flight recorder in-fligh start discrepancy. But what then does the NAC examiner/badge person do? If (like I hope there is) there is a requirement for the FR to be on before flight please provide the rule number.

Thanks

Darryl

Want a bit more concern? Look at my flight from May 13.
http://www.onlinecontest.org/olc-2.0...l?dsId=2355098
Good baseline before takeoff, but it is 400+ meters high. Then, a bit
into the flight, there is a downward vertical correction (19:09:08).
Maybe again the 2D to 3D correction? Then, right after the downward
correction, is a majoor upward correction (19:11:16. There were no 18
knot thermals or even short climbs due to a zoom). Could be that the
inflight corrections were when I move the logger from the panel to the
canopy frame.

Interesting that I have not ever seen any major jumps like that with
the GPS altitude from my Cambridge logger.

Steve Leonard

On Sunday, May 27, 2012 9:08:02 PM UTC-7, Steve Leonard wrote:
Want a bit more concern? Look at my flight from May 13.
http://www.onlinecontest.org/olc-2.0...l?dsId=2355098
Good baseline before takeoff, but it is 400+ meters high. Then, a bit
into the flight, there is a downward vertical correction (19:09:08).
Maybe again the 2D to 3D correction? Then, right after the downward
correction, is a majoor upward correction (19:11:16. There were no 18
knot thermals or even short climbs due to a zoom). Could be that the
inflight corrections were when I move the logger from the panel to the
canopy frame.

Interesting that I have not ever seen any major jumps like that with
the GPS altitude from my Cambridge logger.

Steve Leonard

Steve

FYI there are no position reports (B records) in that file that indicate a 2D fix.

Do you have a trace from the same flight from your Cambridge flight recorder?

Darryl

I have checked both flights and for the first flight it seems to me
that the flight recorder was turned on too late. Every GPS needs some
time to find correct position and when the GPS is moving this time is
even longer. The correct procedure is to turn on the GPS few minutes
before the flight so that GPS could correctly find first position and
will start recording correctly. These jumps could be easily detected
and the recording would be cut off.

In second case the altitude is continuous but with big changes.
Changing the position could have effect. Usually GPS antenna for
flight computer is positioned on perfect spot. Better spot for
flyWithCE Flight Recorder will also result in better results.

Best regards

Uros
www.flywithce.com

On May 28, 11:59*am, uros wrote:
I have checked both flights and for the first flight it seems to me
that the flight recorder was turned on too late. Every GPS needs some
time to find correct position and when the GPS is moving this time is
even longer. The correct procedure is to turn on the GPS few minutes
before the flight so that GPS could correctly find first position and
will start recording correctly. These jumps could be easily detected
and the recording would be cut off.

Uros, if the GPS was engaged in cold/warm start and recording 2D or
degraded fixes, why wasn't the navigation warning flag set (V in
column 24 of the B records)?

Marc

On Monday, May 28, 2012 12:13:57 PM UTC-7, Marc wrote:
On May 28, 11:59*am, uros wrote:
I have checked both flights and for the first flight it seems to me
that the flight recorder was turned on too late. Every GPS needs some
time to find correct position and when the GPS is moving this time is
even longer. The correct procedure is to turn on the GPS few minutes
before the flight so that GPS could correctly find first position and
will start recording correctly. These jumps could be easily detected
and the recording would be cut off.

Uros, if the GPS was engaged in cold/warm start and recording 2D or
degraded fixes, why wasn't the navigation warning flag set (V in
column 24 of the B records)?

Marc

And if the fixes were 2D why was the GPS altitude not recorded as zero. At least that's is a requirement of IGC flight recorders--I'll admit to being lost as to what actual hard specs the NACs are supposed to hold position recorder manufacturers too. I hope the SSA is looking at this.

Darryl

On May 28, 1:59*pm, uros wrote:
I have checked both flights and for the first flight it seems to me
that the flight recorder was turned on too late. Every GPS needs some
time to find correct position and when the GPS is moving this time is
even longer. The correct procedure is to turn on the GPS few minutes
before the flight so that GPS could correctly find first position and
will start recording correctly. These jumps could be easily detected
and the recording would be cut off.

In second case the altitude is continuous but with big changes.
Changing the position could have effect. Usually GPS antenna for
flight computer is positioned on perfect spot. Better spot for
flyWithCE Flight Recorder will also result in better results.

Best regards

Uros
www.flywithce.com

I think the issue I had was likely due to positioning near a cable to
my Cambridge GPS Nav display. Next chance I get, I will repeat the
position and change, noting exact time of change to compare with
changes in reported altitude or position. It is odd that it had
position correct, and altitude offset steady while stationary.

I do like the FlywithCE logger and can hopefully prove that mine was
an error created by installation. Something for us all to be aware
of.

Steve Leonard

On Monday, May 28, 2012 1:59:19 PM UTC-5, uros wrote:
I have checked both flights and for the first flight it seems to me
that the flight recorder was turned on too late. Every GPS needs some
time to find correct position and when the GPS is moving this time is
even longer. The correct procedure is to turn on the GPS few minutes
before the flight so that GPS could correctly find first position and
will start recording correctly. These jumps could be easily detected
and the recording would be cut off.

Sure I know that you should turn it on on the ground but I forgot. And with turning it on in flight of course it will take a little time to "find itself". However why on earth doesn't it wait until it has found itself to start recording fixes? And even then, why was it recording fixes over 2000 ft too high if it had found itself?