Landing Zone
The Johnson Jump Meter System uses three meter sighting stations, and mathematical triangulation of those sighting angles to derive the landing location.

Landing
Zone
The Corson Video Jump Measurement System uses an elevated video camera, and four visible reference marker buoys, whose locations on the water surface are known, relative to that of the jump ramp. Then "Photogrammetric
Translation" can be used to mark any other point on the screen, and determine where that is on the water surface.

Computer Screen view of landing area
Shoreline Shoreline
An Official freezes the video image as the skier lands, and then places a marker on the screen at the point of the landing. The computer then translates that marked screen location back onto the water surface, and then calculates the distance from that point back to the ramp.

Video Camera or Camcorder
Video Cassette
Recorder
Coaxial
Cable
Video
Display
Mouse
Computer CPU with
Video Overlay card.

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 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
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 grid is 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 system uses 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 “Photogrammetric 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 the landing area. Given the grid interaction resulting from the view displayed here, the up-and-down-course displacement from a vertical movement, is greater than for a horizontal movement.

A solution frequently employed for Record Capability competitions is to set up multiple fields of view, each with 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. Compare this view to the one on the following page.

Raising the camera, spreads out the grid lines in the cross-course direction. Just like when the sun is higher in the sky, shadows become shorter. This view is less sensitive.

There are three things that you can do to reduce the sensitivity problem.
Compare the view below, to each of the three views which follow.
1) Elevate the camera. This will
"shorten the shadow" of the vertical movements. As illustrated on the previous page.

Another alternative. As before, compare the view below, to the one to it's right.
2) Move the camera further away from the landing area -- reduces the diagonal angles to the short and long ends of the viewing area.

Another alternative. As before, compare the view below, to the one to it's right.
3) Magnify the view -- "Zoom In" on the landing area. But typically needs multiple views to cover the range of jump distances we see.

Meter system configurations for the Johnson Meter System need to be taylored to the layout of each particular jump site. A wide variety of configurations are possible, and what's ideal for one site may be undesirable elsewhere. Likewise, jump landing area views and the associated camera placement(s) for the
Corson video jump distance measurement system need to be planned around the site configuration and potential elevated observation points at each lake.
The basic operating rule says that any video jump system must be configured so that the maximum differential in jump distances which would result from onepixel 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 Planning and Analysis model in the form of a spreadsheet template. This planning model is available on several Internet Web sites. Look for VJVIEW16.WKS, which may also be found packaged in the VJTOOLS.EXE self-extracting file.

If properly positioned, local tournament precision can be produced with one single camera viewpoint to cover the entire range of local tournament jumps.

For many sites, placing the camera viewpoint(s) on the opposite side of the lake from the "traditional" meter baseline 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.

Cameras on Left
Cameras at
(44,-90) and at 14m Tall
“R” Spec Alternative #1 --
Two overlapping fields of view, covered by two cameras, both placed on one single tall pylon.
(67,-19)
(44,-19)
(35,-19)
(15,-19)
Ramp is at (0,0)
(79,19)
(44,19)
(30,19)
(0,19)

Cameras on Right
(73,-15)
(66,19)
(46,-15)
(29,-15)
(42,19)
(-5,-15)
(15,19)
Ramp is at (0,0)
Cameras at
(50,85) and at 15m Tall
“R” Spec Alternative #1 --
Two overlapping fields of view, covered by two cameras, both placed on one single tall pylon.

Cameras on Left
Cameras at
(50,-65) and at 10m Tall
Cameras at
(28,-65) and at 9m Tall
“R” Spec Alternative #2 --
Two overlapping fields of view, covered by two cameras, each on its own separate pole.
(67,-15)
(41,-15)
(13,-15)
Ramp is at (0,0)
(1,19)
(79,19)
(51,19)
(34,19)

(73,-15)
(47,-15)
(27,-15)
(-3,-15)
(66,19)
(42,19)
Cameras on Right
Camera 2 at
(58,60) and at
9m Tall
Camera 1 at
(38,60) and at
11m Tall
(15,19)
Ramp is at (0,0)
“R” Spec Alternative #2 --
Two overlapping fields of view, covered by two cameras, each on its own separate pole.

Cameras on Left
(67,-15)
Camera 3 at
(57,-45) and at 6m Tall (48,-15)
Camera 2 at
(34,-45) and at 6m Tall
Camera 1 at
(20,-45) and at 6m Tall
“R” Spec Alternative #3 -- Three overlapping fields of view, covered by three cameras, each on its own separate pole.
(29,-15)
(12,-15)
Ramp is at (0,0)
(79,19)
(63,19)
(40,19)
(24,19)
(3,19)

(73,-15)
(56,-15)
(37,-15)
(20,-15)
(-3,-15)
(66,19)
Cameras on Right
Camera 3 at
(60,45) and at
6m Tall
Camera 2 at
(47,45) and at
7m Tall
Camera 1 at
(34,45) and at
7m Tall
(35,19)
(18,19)
Ramp is at (0,0)
“R” Spec Alternative #3 --
Three overlapping fields of view, covered by three cameras, each on its own separate pole.

Easily erectible camera tower for permanent installations. Major component is 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 any sway, 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.
14
The "Nobody Climbs"
Video Camera Pylon.
Lifting arm design, with stabilizing guy wires.
In the Operating
Configuration
30
In the Storage and Servicing
Configuration
20
6
24
5 5