How does Winscore calculate finish altitude?

snip the altitude being displayed on the 302 is the same as being
recorded on the GPS /snip

John, can you confirm that it's the pressure altitude, not GPS
altitude, that's being displayed and recorded?

2NO (finish line fan)

On Jul 27, 1:09 pm, BB wrote:
Yes, actually I did get caught out. I cut the margin a bit too close
(My altimeter showed me about 100 ft above the 500', but I suspect my
altimeter needs recalibration) so lost some points.

A good trick here is to look at the altitude that's being recorded in
the GPS rather than the aircraft altimeter. If you have a 302, the
altitude being displayed on the 302 is the same as being recorded on
the GPS so you know to the last foot exactly what's going on. Most
GPS systems can display altitude, you just have to find where it is
and look at it.

I should have listened to 44 and landed straight in. Less
safe, perhaps, but a better race option.

In most cases, it's the other way around: an early commitment to a
rolling finish is safer than arriving at 501 feet, 1 mile out, and 42
knots, much safer than staring at the altimeter for the last mile or
so if you're unsure you'll even make that, and far safer than
arriving at a finish line over the center of the airport at 50 feet,
50 knots. Was there something unusual at Ionia that turned this usual
advice around?

John Cochrane

Actually, I was crosschecking my SeeYou Mobile AGL readout with my
altimeter. I thought I was just barely above the line. It showed me
close to the 500', but there is a definite lag in the display. I may
have to reconfigure the display to show straight GPS altitude and
practice with that. Again, the problem is that if you are trying to
win, you have to spend precious time clockwatching at a critical point
of the flight. And on a weak day, 100ft could be as much as a
minute. Yeah, it makes a difference!

Of course, Winscore doesn't use GPS altitude, but pressure altitude.
So you have to hope that there isn't a significant difference between
your logger pressure altitude reading while stopped, and while moving
(I have yet to see a logger hooked up to a static port - have you? I
wonder what the static pressure is in my cockpit on final
glide...fast=more ram pressure=lower altitude? It only takes a few
feet...).

At this particular race, the CD did not set a rolling finish penalty
(and was asked to confirm it prior to the flight in question). I
would easily have saved 2 - 3 minutes (!) by ignoring the 500'
requirement altogether (even though I wasn't really low and slow
enough to need to), pushing over to the deck, pulling spoilers
crossing the fence, planting my glider on the first piece of runway
available, and coming to a screeching halt. Safe? Probably not.
Smart racing? Absolutely! That's one of the reasons I really question
this finish rule and think it needs to be re-addressed - it's got a
few huge loopholes in it!

I realize that to some this may seem to be arguing about angels on a
pinhead, but in racing, seconds really do count - so we shouldn't have
rules that introduce a large unknown in the scoring equation.

IMHO, of course ;^)

Kirk
66

On Jul 27, 12:15 pm, Tuno wrote:
snip the altitude being displayed on the 302 is the same as being
recorded on the GPS /snip

John, can you confirm that it's the pressure altitude, not GPS
altitude, that's being displayed and recorded?

It's ALWAYS the pressure altitude that's recorded. The altitude
displayed on the 302 is pressure altitude adjusted for the local
altimeter setting.

So unless there is an accurate source of local pressure nearby, it's
impossible to know precisely how high you are at the end of the day.

-Tom

While Scoring the Region 8 contest I asked this exact question. I
think I talked to Guy about it but now I don't remember, it might have
been one of the previous scorers in attendance.

I confirmed that the finish alititude is caluclated off the feild
elevation at the beginning of the flight. The theory I heard for
this is that the pressure typically changes through out the day to
make calculating it this way generally give the pilot the benefit of
the doubt.

I confirmed this on several flight logs that had low finishes, that if
it had calculated it on the landing elevation the program would have
scored the finish even lower.


Now the feature that I and several other pilots disagreed with was
scoring a low finish as a Rolling Finish. I am not sure where this
practice comes from but it seems like a poor practice to me. It means
that the pilot that is 10 feet low on the finish and doesn't realize
it get penalized for coming back to the airport and flying a normal
pattern because he doesn't realize the clock is still running. What
this practice promotes is if a pilot is even close to being low they
are encouraged to dive for the runway and land as soon as possible to
get the clock stopped.

In my opinion the clock should stop as soon as the pilot enters the
cylinder. We shouldn't have pilots in the finish cylinder still
racing.

Brian
CFIIG/ASEL

Brian wrote:
I confirmed that the finish alititude is caluclated off the feild
elevation at the beginning of the flight. The theory I heard for
this is that the pressure typically changes through out the day to
make calculating it this way generally give the pilot the benefit of
the doubt.

I confirmed this on several flight logs that had low finishes, that if
it had calculated it on the landing elevation the program would have
scored the finish even lower.

I looked at the source code for the 2007 version of Winscore, it looks
to me like it uses the most favorable (to the pilot) of the field
elevation corrections determined by looking at samples from 2 minutes
before takeoff, and 2 minutes after landing, to calculate the finish
altitude.

In my opinion the clock should stop as soon as the pilot enters the
cylinder. We shouldn't have pilots in the finish cylinder still
racing.

That seems like a sensible change to me. In any case, it absolutely
defeats the whole purpose of the finish cylinder if the CD does not
penalize rolling finishes by an amount greater than the time it would
take to climb to the bottom of the cylinder...

Marc

In the past, you region 8 guys have used a graduated
finish penalty something like;
100 foot low = 5 points
200 foot low = 10 points
300 foot low = 15 points
400 foot low = 20 points

I didn't like it because it wasn't in the rules. Might
be time to put something like this in the rules???

I have tried to use GPS pressure altitude and ended
up with a penalty. Things get complicated, you must
read GPS pressure altitude before flight, note correction
(+125 feet or - 236 feet), apply the corrected GPS
pressure altitude to the start and finish pressure
altitude, then select GPS pressure altitude to view
when starting or finishing. Oh, also you need to display
the start/finish distance at the same time. Much toooo
complicated for me, also like kirk said, the GPS isn't
hooked to the ships static system, but your altimiter
is, sooooo set it to field elevation before takeoff
and use it because it's the most accurate information
available, then apply an appropriate margin for error.
JJ

At 20:18 27 July 2007, Brian wrote:
While Scoring the Region 8 contest I asked this exact
question. I
think I talked to Guy about it but now I don't remember,
it might have
been one of the previous scorers in attendance.

I confirmed that the finish alititude is caluclated
off the feild
elevation at the beginning of the flight. The theory
I heard for
this is that the pressure typically changes through
out the day to
make calculating it this way generally give the pilot
the benefit of
the doubt.

I confirmed this on several flight logs that had low
finishes, that if
it had calculated it on the landing elevation the program
would have
scored the finish even lower.


Now the feature that I and several other pilots disagreed
with was
scoring a low finish as a Rolling Finish. I am not
sure where this
practice comes from but it seems like a poor practice
to me. It means
that the pilot that is 10 feet low on the finish and
doesn't realize
it get penalized for coming back to the airport and
flying a normal
pattern because he doesn't realize the clock is still
running. What
this practice promotes is if a pilot is even close
to being low they
are encouraged to dive for the runway and land as soon
as possible to
get the clock stopped.

In my opinion the clock should stop as soon as the
pilot enters the
cylinder. We shouldn't have pilots in the finish cylinder
still
racing.

Brian
CFIIG/ASEL

In my opinion the clock should stop as soon as the pilot enters the
cylinder. We shouldn't have pilots in the finish cylinder still
racing.


You haven't met enough contest pilots. If the rules change in this
way, pilots will aim to finish one mile out, 50 feet, 90 knots and
then float in to the landing, european-style.

If you don't think people racing inside the cylinder is a good idea,
then what you want is a "hard floor". 499 feet = distance points only.
Now, again, everybody inside 1 mile is done racing, but pilots aim for
500 feet, not for 50 feet.

John Cochrane

BB wrote:
In my opinion the clock should stop as soon as the pilot enters the
cylinder. We shouldn't have pilots in the finish cylinder still
racing.


You haven't met enough contest pilots. If the rules change in this
way, pilots will aim to finish one mile out, 50 feet, 90 knots and
then float in to the landing, european-style.

Applying an appropriate penalty for finishing below the Minimum Finish
Height would eliminate that behavior. I was actually surprised to find
that the SSA competition rules provide no guidelines as to how to
penalize pilots who don't make it into the finish cylinder. Given the
difficulties of knowing precisely how high one is finishing, missing by
50 or so feet shouldn't result in a huge penalty, but it should also
never be beneficial to intentionally finish low...

Marc

A question: How does Winscore calculate finish altitude on a cylinder
finish?

Winscore calculates altitudes and finish heights according to SSA
Contest rules 6.7.4.3 and 11.2.1.5.1.

6.7.4.3 If a Flight Recorder records both calculated and pressure
altitude, pressure altitude
will be the primary data source and calculated altitude will be the
backup data source for
flight evaluation.

11.2.1.5.1 When the Scorer must measure a pilot's height above ground
level (AGL),
this height shall be the difference between a recorded fix and that of
a fix recorded on
the ground. For all purposes except finish height, a fix prior to
takeoff shall be used. For
finish height, the Scorer shall use the more favorable of a pre-
takeoff or post-landing fix.

Guy Byars
Author of Winscore

On Jul 28, 6:44 am, wrote:
A question: How does Winscore calculate finish altitude on a cylinder
finish?

Winscore calculates altitudes and finish heights according to SSA
Contest rules 6.7.4.3 and 11.2.1.5.1.
....
Guy Byars
Author of Winscore

Winscore calculates altitudes and finish heights according to SSA
Contest rules 6.7.4.3 and 11.2.1.5.1.
...
Guy Byars
Author of Winscore

What does winscore do about

6.7.4 Altitude recording
6.7.4.1 A Flight Recorder may record altitude derived
from a calculated position. The estimated altitude inaccuracy shall be
applied in a way unfavorable to the pilot (if the flight log does not
include a reliable estimate of this inaccuracy, a value of 75 feet
shall be used).
6.7.4.2 A Flight Recorder may record a calibratable
pressure altitude. If such a device is used in circumstances where
altitude is needed, the altitude inaccuracy determined from the best
available calibration data shall be applied in a way unfavorable to
the pilot.
6.7.4.3 If a Flight Recorder records both calculated
and pressure altitude, pressure altitude will be the primary data
source and calculated altitude will be the backup data source for
flight evaluation.

I've never really understood these rules. Does winscore subtract 75
feet from GPS altitude in deciding if you get a penalty (or add it for
start gates and 17500?) I've never submitted calibration data at a
contest, does 6.7.4.2. apply anywhere?

John Cochrane