Date: Wed, 25 Aug 1993 21:11:03 -1000
From: salanne@convex.csc.FI (Simo Salanne)
Message-Id: <1993Aug26.071103.29598@nic.funet.fi>
Organization: Finnish Academic and Research Network Project - FUNET
Subject: Parallax distortion in judging
Position of the judges in a competition?
----------------------------------------
A couple of months ago Ron Reich wrote in one of his exellent
postings:
"CONSIDERATION MUST BE GIVEN TO THE POINT OF VIEW OF
THE JUDGES. i.e. The picture to the flyers may
need to be slightly distorted in order to present an
appropriate picture to the position of the judges."
This evening was rainy and I (finally) studied the distortion
matter. I selected a compulsory figure called 'Square Cuts' as
the case. Square Cuts looks like this:
----------------------<
|
v1
|
--------
|
v2
|
--------
|
v3
|
--------
|
v4
|
<----------------------
When the figure is flown, the kite is on spherical surface and
the flyer is in the center of the sphere. Let's suppose we have a
perfect flyer and HE SEES the vertical and horizontal cuts
having equal lenghts.
I'll simplify the model and concentrate only on vertical cuts
(v1, v2, v3, v4) and suppose them to happen in the same vertical
plane with the flyer and the judge (i.e. zero lenght horizontal
cuts). The side view is like:
1
1
2
2
3
3
4
4
J F
===========================================================
where J is judge, F is flyer, the numbers indicate the end points
of vertical cuts.
Flyer sees the vertical cuts as equal lengths; it means the angles
1-F-1, 2-F-2, 3-F-3 and 4-F-4 are equal. But how the JUDGE
SEES vertical cuts? For practical reasons the judge cannot stay
on the same spot as the flyer. What is the effect of the distance
between flyer and judge?
I suppose the figure is started at level where the flying lines
make 70 deg angle with ground and the ground pass will be at
1.5 deg i.e. about 1 meter. I compared the lengths of v1 to
v4 as the judge will see them at different distances from flyer.
If I made my trigonometry right, the maximum distorsion
(difference in apparent lenghts) of 8 appens when the
judge is 0.4 times the line lengt behind the flyer. If the judge
comes closer the distorsion comes smaller. If the judge goes
further, the distorsion comes smaller until AT THE LINE
LENGTH IT IS ZERO! And then starts growing again, beeing
15 at 2 times the line length.
If you want to construct the distorsion curve, here is the
data:
Distance Distortion
0.0 0.0
0.1 4.1
0.2 6.6
0.3 7.8
0.4 8.0
0.5 7.4
0.6 6.4
0.7 5.0
0.8 3.4
0.9 1.7
1.0 0.0
1.1 1.7
1.2 3.4
1.3 5.1
1.4 6.7
1.5 8.3
1.6 9.7
1.7 11.1
1.8 12.5
1.9 13.7
2.0 14.9
Distance is in units of line lenght.
A few questions to the rec.kiters:
1. Is my analysis correct? Could somebody make it independently
of my formulas and report to us, please!
2. How many competitive flyers out there are 'distorting'
the figures to make them look correct to judges?
How do you quesstimate the amount of distortion?
3. How many of judges out there, know how the distance will
affect to the distortion? Is 8 0ifference noticeable?
4. I analysed only vertical cuts in the figure. What happens
to horizontal cuts when the judge departs from the flyer?
My model only considered one judge and one flyer, when
five flyers and five judges are on the field, the geometry is 25
times more complicated!
Knowledge hurts...
Smooth Winds
Simo.Salanne@csc.fi
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Date: Thu, 26 Aug 1993 03:35:56 -1000
From: salanne@convex.csc.FI (Simo Salanne)
Message-Id: <1993Aug26.133556.9658@nic.funet.fi>
Organization: Finnish Academic and Research Network Project - FUNET
Subject: Re: Parallax distortion in judging
In <25iejp$41p@news.umi.com> sritter@umi.com (Sam Ritter x3111) writes:
>>
>>A few questions to the rec.kiters:
>>
>>1. Is my analysis correct? Could somebody make it independently
>> of my formulas and report to us, please!
> This sounds good, but should it matter in individual competition?
> You may have judges placed liked the following diagram:
> J(udge)
> J
> J F(lyer) Kite
> J
> J
> With this placement, which judge should the flyer fly the figure for?
Let's suppose my distortion curve is correct. Then it suggest e.g.
following placement for minimal distortion:
J
J J F K
J J
Judging guidelines could recommend this kind of placement, flyer
can avoid (?) such a line lenght, which yields to unfavourable positioning
etc... Actually I did not think any figure by figure distortion analysis,
just general understanding of the bad and good spots.
> set of positions of the judges panel. Can we add a rule for the judges
> that says they must all stay within arms length of each other for
> precision?
It should be possible to be in judging guidelines, if there is a good reason.
>Sorry if this came off as a flame, I definitely don't want it to be. These are
>just my views.
Not at all, I asked opinions, and hope we'll get some more now,
when you are awake over there.
BTW, I have beautiful weather now, I can go to 'distort'
my figures in the air instead of a computer:-)
Smooth Winds
Simo
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Date: Thu, 26 Aug 1993 05:32:24 -1000
From: sasaki@netop3.harvard.edu (Marty Sasaki)
Message-Id: <1993Aug26.153224.14235@das.harvard.edu>
Organization: Harvard University
Subject: Re: Parallax distortion in judging
In article <1993Aug26.071103.29598@nic.funet.fi>, salanne@convex.csc.FI (Simo Salanne) writes:
>1. Is my analysis correct? Could somebody make it independently
> of my formulas and report to us, please!
The mathematics aren't really that important except to give an idea of
what the distortion factor is like. No one flys exactly enough to be
able to tell the difference of a few percent anyway.
>2. How many competitive flyers out there are 'distorting'
> the figures to make them look correct to judges?
> How do you quesstimate the amount of distortion?
As Ron mentions, for team flying it is really important to distort
figures slightly. Once we get the hang of a move, then we start
tweaking it to make it look better to the judges. This can get really
complicated when you consider unequal length lines and try to factor
in ground position.
>3. How many of judges out there, know how the distance will
> affect to the distortion? Is 8 0ifference noticeable?
Fortunately, most of the precision compulsories are near the center of
the window, which minimizes the effects of the distortion. Judges
should try to stay near the competitor, which is usually pretty easy
with compulsories, unless the wind is light.
There has been similar work done with control line and RC model
airplane aerobatics.
A computer simulation with real time graphics would go a long way at
highlighting this problem. For now I just fly the figures as perfectly
as I can from my point of view individually. For team, we do a bit of
warping and try to take the point of view of a judge standing right
between flyers 2 and 3.
--
Marty Sasaki Harvard University Sasaki Kite Fabrications
sasaki@noc.harvard.edu Network Services Division 26 Green Street
617-496-4320 10 Ware Street Jamaica Plain, MA 02130
Cambridge, MA 02138-4002 phone/fax: 617-522-8546
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Date: Thu, 26 Aug 1993 03:42:17 -1000
From: sritter@umi.com (Sam Ritter x3111)
Message-Id: <25iejp$41p@news.umi.com>
Organization: University Microfilms Inc.
Subject: Re: Parallax distortion in judging
In article <1993Aug26.071103.29598@nic.funet.fi> salanne@convex.csc.FI (Simo Salanne) writes:
>
[ Stuff deleted about figure ]
>
>
>A few questions to the rec.kiters:
>
>1. Is my analysis correct? Could somebody make it independently
> of my formulas and report to us, please!
This sounds good, but should it matter in individual competition?
You may have judges placed liked the following diagram:
J(udge)
J
J F(lyer) Kite
J
J
With this placement, which judge should the flyer fly the figure for?
This type of question may bring us back to the point of when is the
judging panel going to consist of mainly professional judges. I also
think that most people can't make these calculations for a varying
set of positions of the judges panel. Can we add a rule for the judges
that says they must all stay within arms length of each other for
precision?
>
>2. How many competitive flyers out there are 'distorting'
> the figures to make them look correct to judges?
> How do you quesstimate the amount of distortion?
When I fly precision, I don't distort the figures, or at least I don't
try to. Unless we have some true Einsteins out there, that can
calulate all the angles, distances, and distortions for each figure
( they will change ), everyone guesstimates a distortion factor if any.
>3. How many of judges out there, know how the distance will
> affect to the distortion? Is 8 0ifference noticeable?
The figures definitely get distorted when the judges are not directly
behind the flyer. In an ideal situation, judges about 10-15 ft behind
the ind. flyer and the kite on 120ft fly lines for precision, any
distortion in a figure like the square cuts should be minimal and not
be noticed.
>
>4. I analysed only vertical cuts in the figure. What happens
> to horizontal cuts when the judge departs from the flyer?
>
>My model only considered one judge and one flyer, when
>five flyers and five judges are on the field, the geometry is 25
>times more complicated!
This is where the distortions really come into play. In the short time
that I have been flying and going to these competitions, I've noticed
that the judges are typically about 20yrds behind the team. This
gives the team their moving room. The main criteria behind team
flying is the visual impact that the 3-(however many) kites can
produce for the judges and spectators. This is where "fly the space"
comes in( Thanks Ron ). Take a look at THP's flyin cross formation and
Flight Squadron's wide array of formations. To the judges and
spectators, they look perfectly spaced, but are they flying the
formation perfectly spaced? They fly it distorted from their
perspective.
>
>Knowledge hurts...
>
>Smooth Winds
>Simo.Salanne@csc.fi
>
>
>
Sorry if this came off as a flame, I definitely don't want it to be. These are
just my views. I am one of those people that believe precision flying does
have a place in this sport. I am not really sure that so much time should be
spent on it at events. Precision flying is noticed in ballet routines.
Precision flying comes as a part of making that kite do what you want it to do
when you want/need it to do it.
Good winds and keep those lines tight.
Sam Ritter
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Date: Thu, 26 Aug 1993 23:10:12 -1000
From: david@camscan.co.uk (David Sansom)
Message-Id: <1606.9308270910@bendix.camscan.co.uk>
Organization: Division of Applied Sciences, Harvard University
Subject: Re: Parallax distortion in judging
Hi,
I don't know about kite aeros but in aeroplane aerobatics the figures are
often flown to be seen to be correct from the judges position and may be
"sloppier" as seen from another position or considering the perfect figure.
Dave
-------------------------------------------------------------------------------
Dave Sansom (david@camscan.co.uk) ________|________
PPL(A) -(*)-
C152/PA28 driver /!\
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =