Part 1 -- IntroductionPart 2 -- Equipment NeedsPart 3 -- Conceptual FoundationPart 4 -- Site Setup & PlanningPart 5 -- Camera Pylon Ideas

Corson Video Jump DistanceMeasurement System -- Diagrams

The Johnson Jump Meter System uses three metersighting stations, and mathematical triangulation ofthose sighting angles to derive the landing location.

Landing Zone

The Corson Video Jump Measurement System uses anelevated video camera, and four visible reference markerbuoys, whose locations on the water surface are known,relative to that of the jump ramp. Then "PhotogrammetricTranslation" can be used to mark any other point on thescreen, and determine where that is on the water surface.

Landing Zone

ShorelineShoreline

Computer Screen view of landing area

An Official freezes the video image as the skier lands, and then placesa marker on the screen at the point of the landing. The computer thentranslates that marked screen location back onto the water surface,and then calculates the distance from that point back to the ramp.

VideoDisplay

Mouse

Video Cassette Recorder

Computer CPU withVideo Overlay card.

Video Camera or Camcorder

CoaxialCable

Equipmentand Hookup

Corson Video Jump Distance MeasurementSystem -- Required Equipment List

For Original “Freeze Frame” software:

ISA Bus & Video Feature Connector Creative Labs "Video Blaster" card 486/25 processor (or faster) 8 mb ram recommended Windows 3.x or later operating system VGA color video display monitor Keyboard and mouse

Home video camera(s) or camcorder(s) -- one per field of view, if using multiple views -- high speed shutter desirable.

Videocassette Recorder(s) -- one per camera.

Coaxial cable sufficient to reach from camera location(s) to protected area where computer and recording equipment will be operated.

Suitable IBM-Compatible Personal Computer System -- Two options:

For Newer “Capture Clip and Select Frame” software:

Pentium system with PCI Bus or USB PCI or USB Video Capture Card 32 mb ram recommended Windows 95 or later operating system VGA color video display monitor Keyboard and mouse

Camera view of landing area, with illustration of a a coordinate grid on the water surface. This gridis rectangular, and indicates ABSOLUTE locations on the water surface -- as opposed to the curved lines on the “Masterboard Grid” template, which was portraying distances from the ramp.

This overlay superimposes a grid of "Pixel” locations on the computer video screen, on top of the water surface coordinate grid. The Johnson meter systemuses protractors, which are graduated in tenths of a degree. The Corson video system uses this grid of pixels as the foundation for measurement. Notice that the view includes four “Reference Marker Buoys”.

We will need to give the computer the water surface coordinates of these four reference buoys. We also need to show the computer where these buoys appear on the computer screen grid. Once it has those two corresponding sets of coordinates, the computer can then use a mathematical process known as “Photo-grammetric Translation”, to translate between ANY other marked point on the computer screen, and the corresponding point on the water surface grid.

The precision and accuracy in translating between these two grids -- between points in the screen grid,and the corresponding points on the water surface -- will depend on the location of the camera and it's field of view. How much difference is there, between two adjacent points on the screen grid? This is THE most critical issue in planning and using the Corson Video system. So let’s explore this issue in more detail.

Let’s examine the effect of moving between two adjacent grid points (one pixel apart) on the screen. Side to side, you can see that moving one pixel sideways, will be about the same horizontal distance on the water surface, at ANY point along the landing line. Compare the three indicated points below.

However ... Vertical movements are different. That will depend on where you are on the screen. Near the center of the grid, adjacent vertical pixels are both about the same distance from the ramp. But that’s not true at either the short or long end of the view. Compare the vertical movement effect at the center of the grid, with the effect of the same vertical movement at either the short or long end of the view.

Magnified view of grid interactions, near the long end of thelanding area. Given the grid interaction resulting from the view displayed here, the up-and-down-course displacement from avertical movement, is greater than for a horizontal movement.

A solution frequently employed for Record Capabilitycompetitions is to set up multiple fields of view, eachwith it's own camera mount and reference markers.Does the job, but takes lots of equipment. Complex.

But there ARE other solutions to this problem.

Here's the original grid view again. Comparethis view to the one on the following page.

Raising the camera, spreads out the grid linesin the cross-course direction. Just like whenthe sun is higher in the sky, shadows becomeshorter. This view is less sensitive.

1) Elevate the camera. This will"shorten the shadow" of the verticalmovements. As illustrated on theprevious page.

There are three things that you cando to reduce the sensitivity problem.Compare the view below, to each ofthe three views which follow.

Another alternative. As before,compare the view below, to theone to it's right.

2) Move the camera further awayfrom the landing area -- reducesthe diagonal angles to the shortand long ends of the viewing area.

3) Magnify the view -- "Zoom In"on the landing area. But typicallyneeds multiple views to cover therange of jump distances we see.

Another alternative. As before,compare the view below, to theone to it's right.

Meter system configurations for the Johnson Meter System need to be tayloredto the layout of each particular jump site. A wide variety of configurations arepossible, and what's ideal for one site may be undesirable elsewhere. Like-wise, jump landing area views and the associated camera placement(s) for theCorson video jump distance measurement system need to be planned aroundthe site configuration and potential elevated observation points at each lake.The basic operating rule says that any video jump system must be configuredso that the maximum differential in jump distances which would result from one-pixel movements on the video screen, not exceed the value "X", at any point in that "operating field of view", which means the central 80% of the screen area.The value "X" depends on the class of the tournament, as follows:

World Record (Class "R"): 10 centimeters (about 4 inches) Standing List (Class "L"): 15 centimeters (about 6 inches) Local Tournaments (Class "C") 20 centimeters (about 8 inches)

As an aid to evaluating any proposed site configuration against this standard,the AWSA Technical Committee has prepared a Video Jump System Planningand Analysis model in the form of a spreadsheet template. This planning modelis available on several Internet Web sites. Look for VJVIEW16.WKS, whichmay also be found packaged in the VJTOOLS.EXE self-extracting file.

If properlypositioned, localtournament precision can beproduced with one single cameraviewpoint to cover the entirerange of local tournament jumps.

For many sites, placing the camera view- point(s) on the opposite side ofthe lake from the "traditional" meterbaseline may provide the necessary"further back" camera sightline(s).

However, Record Capability precision will typically require either two or three cameras. Based on what you’ve seen in the preceding diagrams regarding sensitivity, in general, placing the camera(s) higher up and/or further away from the landing area will work best. Exactly where the cameras are positioned, and how the reference grids need to be set up, depends on how much room is available on the site, and what the lay of the land is like. Six alternatives layouts follow. Each of these has been validated for “R” precision. Choose one of these, or at least use these as a starting point for customizing to your own needs, but in that case DO use the VJVIEW16.WKS verification spreadsheet tool mentioned earlier in this presentation.

Planning your Video Measurement Layout

“R” Spec Alternative #1 -- Two overlapping fields of view, covered by two cameras, both placed on one single tall pylon.

(0,19)

(30,19)

(44,19)

(35,-19)

(79,19)

(15,-19)

(67,-19)

(44,-19)

Cameras at (44,-90) and at 14m Tall

Cameras on Left

Ramp is at (0,0)

“R” Spec Alternative #1 -- Two overlapping fields of view, covered by two cameras, both placed on one single tall pylon.

Cameras at (50,85) and at 15m Tall

(46,-15)

(29,-15)

(42,19)

(-5,-15)

(73,-15)

(15,19)

(66,19)

Cameras on Right

Ramp is at (0,0)

“R” Spec Alternative #2 -- Two overlapping fields of view, covered by two cameras, each on its own separate pole.

(1,19)

(34,19)

(51,19)

(79,19)

(13,-15)

(67,-15)

(41,-15)

Cameras at (50,-65) and at 10m Tall

Cameras at (28,-65) and at 9m Tall

Cameras on Left

Ramp is at (0,0)

“R” Spec Alternative #2 -- Two overlapping fields of view, covered by two cameras, each on its own separate pole.

Camera 1 at (38,60) and at 11m Tall

(47,-15)

(27,-15)

(42,19)

(-3,-15)

(73,-15)

(15,19)

(66,19)Camera 2 at (58,60) and at 9m Tall

Cameras on Right

Ramp is at (0,0)

“R” Spec Alternative #3 -- Three overlapping fields of view, covered by three cameras, each on its own separate pole.

(3,19)

(24,19)

(79,19)

(12,-15)

(67,-15)

(29,-15)

Camera 3 at (57,-45) and at 6m Tall

Camera 1 at (20,-45) and at 6m Tall

Camera 2 at (34,-45) and at 6m Tall

(63,19)

(40,19)

(48,-15)

Cameras on Left

Ramp is at (0,0)

“R” Spec Alternative #3 -- Three overlapping fields of view, covered by three cameras, each on its own separate pole.

Camera 3 at (60,45) and at 6m Tall

(35,19)

(56,-15)

(18,19)

(66,19)

Camera 2 at (47,45) and at 7m Tall

Camera 1 at (34,45) and at 7m Tall

(37,-15)

(20,-15)

(-3,-15)

(73,-15) Cameras on Right

Ramp is at (0,0)

Easily erectible camera tower for permanent installations. Major componentis a 35 foot utility pole, buried 5 feet deep in the ground. Swing arm is a 20’length of 2" pipe or conduit, attached with a pivoting bracket 24 feet above ground level. Bracket is a 6" square of metal with holes in all four corners,with two opposite corners folded up 90 degrees. Add a pulley at the top rear of the pole, plus a small winch on the backside of the pole. When arm is pulled up and tensioned with the winch, the arm is pulled into a cradle bracket at the front of the top of the pole, which provides side to side rigidity. 3 guy wires to earth anchors eliminate anysway, and completely immobilize the camera. This design provides the necessary operating elevation and camera stability, yet also offers easy camera installation and adjustment, working at ground level.

2030

5

14

6

24

5

In the OperatingConfiguration

In the Storageand ServicingConfiguration

The "Nobody Climbs" Video Camera Pylon.Lifting arm design, with stabilizing guy wires.