[NSRCA-discussion] APPARENT GEOMETRY (PARALLAXED VIEW)
george w. kennie
geobet at gis.net
Tue Apr 10 14:05:10 AKDT 2007
Nope, Fred's right. The thing that everybody's missing is that the two planes, if at the extreme end of the box, present the same perspective. The guy that's only 5 feet from the flight line is only 10 feet from the pilot to avoid violating the box while the guy at 175 yards is 800 feet from the pilot. The angles are identical producing the same exact parallax. Eh?
G.
----- Original Message -----
From: DaveL322 at comcast.net
To: NSRCA Mailing List
Sent: Tuesday, April 10, 2007 2:30 PM
Subject: Re: [NSRCA-discussion] APPARENT GEOMETRY (PARALLAXED VIEW)
Fred,
Our respective statements are not mutually exclusive. I don't disagree with your comments as stated below for a model at center.
Keith's original comment was about the effects of parallax at the end of the box......and he is correct.
Dave
-------------- Original message --------------
From: "Fred Huber" <fhhuber at clearwire.net>
A 1/2 size model at half distance at the same angle... will look exactly the same.
If the model is at half distance and same height... then the angle has changed. If it is at a 60 deg angle when at 170 meters out, it will be at 30 deg if its 85 meters out but the same altitude.
There is a difference between distance and angle. Parallax is ALL about the angles. distance is irrelevant.
----- Original Message -----
From: DaveL322 at comcast.net
To: NSRCA Mailing List
Sent: Tuesday, April 10, 2007 12:03 PM
Subject: Re: [NSRCA-discussion] APPARENT GEOMETRY (PARALLAXED VIEW)
Absolute height of maneuvers unchanged, the parallax of 60 inch model at 170 yards is not the same as a 60 inch model at 85 yards.
Dave
-------------- Original message --------------
From: "Fred Huber" <fhhuber at clearwire.net>
Its basic geometry... similar triangles.
----- Original Message -----
From: Keith Black
To: NSRCA Mailing List
Sent: Tuesday, April 10, 2007 2:31 AM
Subject: Re: [NSRCA-discussion] APPARENT GEOMETRY (PARALLAXED VIEW)
Fred, are you suggesting that a 45 degree angle at the end of the box would appear the same if the plane is five feet in front of the flight line or 500 feet in front of the flight line? I don't buy it.
Keith
----- Original Message -----
From: Fred Huber
To: NSRCA Mailing List
Sent: Monday, April 09, 2007 11:41 PM
Subject: Re: [NSRCA-discussion] APPARENT GEOMETRY (PARALLAXED VIEW)
Distance in/out has no effect on parallax. Its the angle relative to the viewed line.
The judges and pilots will have the same parallax to deal with if the pilot flys a 30 inch model at 85 yards away as they will with a 60 inch model at 170 yards. You might be hard pressed to tell plane which is which on film... Thats why 1/4 and 1/2 scale models get used for making movies. The camera can remove perspective clues that indicate distance and scale.
----- Original Message -----
From: Keith Black
To: NSRCA Mailing List
Sent: Monday, April 09, 2007 11:24 PM
Subject: Re: [NSRCA-discussion] APPARENT GEOMETRY (PARALLAXED VIEW)
I tend to agree with Ed. Furthermore, what hard facts could possibly be stated about this in the rule book? Would you want it to say that when observing end maneuvers the judge should downgrade if the angle doesn't look steeper than 45 deg.? IMO this is inappropriate for the rule book, though it's perfectly acceptable to point out in a judges clinic or judging tips document.
Keep in mind also that the distance in our out will also change the look of the end 45 deg. angle. This means that this discussion also would need to be in the rule book. I think the rule book should just state facts, educating the pilot and judge on how to recognize geometry so they can enforce the rule book is important but ancillary to the official rule book.
My opinion.
Keith Black
----- Original Message -----
From: Ed Deaver
To: NSRCA Mailing List
Sent: Monday, April 09, 2007 11:04 PM
Subject: Re: [NSRCA-discussion] APPARENT GEOMETRY (PARALLAXED VIEW)
Have been thinking about this discussion (currently going on elsewhere also) and suddenly had the light bulb go on.
At some clubs as we enter the driveway that leads to the field, 1/2 mile away or maybe a bit more, or the NATs site for example from site 3 (grass field I think) to site 2, it is very easy to watch the geometry of the plane being flown. At this distance, there is almost zero vertical parallax due to the distance from the pilot.
Sooooo, what do we see at this distance. Loops sure do look round to me when flown by good pilots, 45's look like 45's or maybe 50's (my contention is a slight bit steeper always scores better than a slight bit flatter) and even though the pilot is standing "under" the manuever, the good pilots still keep the geometry when looked at from a distance, Correct.
At the end of the box, standing this distance away it is easier to see the geometry again, with only a very little parallax and the good pilots, IMO still keep the geometry very close to what it should be. The 45's may be a slight bit steeper, but from a distance the 1/2 cuban 8 flown well, will still have a round radius, with very close to a 45 degree downline (again depending on what the local teacher states), with the rolling element centered.
My point is, too much is being made of this parallax issue and think judges will reward the pilot that flies the correct geometry, which again IMO, can be verified by watching a flight from a distance.
Just my $.02
Ed
rcmaster199 at aol.com wrote:
A question has been posted from an IMAC gentleman (who is trying to write better IMAC rules) as to how Pattern people fly and judge skewed appearance of maneuvers at box ends or in center when tall maneuvers (Hourglass, Vert Sq 8, Rolling Ess, etc) are involved.
Some of us have searched the book and found no wording written that describes what the pilots' responsibilities and the judges' responsibilities are in the performance of the skewed apparent geometry. There is a statement in the Judges Training tape in regard to end maneuvers.... that these will appear different even when accurately flown. The oness is essentially on the judges to know how the True Geometry should appear when flown at an angle to the eye, and must not downgrade for Apparent or Parallaxed appearance difference.
Spoke with Don about this earlier today and we decided to present the question to the group and get some conversation going. We should be explicit in the book regarding how such Apparent Geometry should be treated....ie- what is the pilot's responsibility and what is the judge's. Description improvements could be written over the next couple rule cycles.
The pilot's responsibility may appear easy.... they simply need to fly precise geometry per the book. True enough, BUT.....consider what is actually flown, especially by the top guys, and what scores well. These are not necessarily as precise as one might think. The better pilots tend to fly purposely flawed maneuvers that give the impression of precision.
MattK
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