## Saturday, January 16, 2010

### Mathematics at the Tennis

Okay let's talk about speed. Not the speed of a person's heartbeat as they watch an exciting tennis match, but how fast a tennis ball goes when it is served.

Big Passy has been very busy at the Australian Open Tennis Tournament, conducting some highly in-depth research for this blog post:

(See the Wondershare Photo Slideshow at the end of this post for further details).

Tennis Serve Speed

At the 2010 Australian Open, IBM are supplying the serve speed technology.

From IBM's own website:

"For fans and players who need to know how serves measure up to Roddick's record-breaker in 2006, IBM provides the Speed-of-Serve Radar. Radar guns behind the server record the ball's speed within millimetres of it leaving the racket. The information flashes onto courtside screens in under a second, reaching the official Web site and the world's TV screens a second or two later.

• The ball's speed is measured within millimetres of leaving the racket

• The radar guns are positioned on the court in a static position behind the servers.
• The speed of the serve is flashed up on courtside screens in less than a second.
• Andy Roddick (USA) and Greg Rusedski (GBR) share the world's fastest serve clocked at 241.4 kph.
Data travels to the official Australian Open website in seconds. The integrated scoring solution is but one of the measurements used in putting together the match analysis DVD, to assist coaches and players improve their game".

The radar used in sports like tennis is basically the same as the Radar that Police use to measure speeding cars. The Radar typically locates a speed within 1/100 of a second after a target is put in motion. (Eg. Immediately when the player's raquet hits the ball). The radar then continuously tracks the target, producing a reading 100 times a second. This way it doesn't miss the fastest speed or the final speed.

The following information is from:
Go to that link to get a deeper discussion about radar guns as well as radar gun detectors, and more sophisticated ways of measuring speed using Lidar Guns.

A basic radar speed gun is just a radio transmitter and receiver combined into one unit. A radio transmitter is a device that oscillates an electrical current so the voltage goes up and down at a certain frequency.

This electricity generates electromagnetic energy, and when the current is oscillated, the energy travels through the air as an electromagnetic wave. A transmitter also has an amplifier that increases the intensity of the electromagnetic energy and an antenna that broadcasts it into the air.

Radar can be used to measure the speed of an object, due to a phenomenon called Doppler shift. You've probably noticed the pitch of an ambulance siren rise as it approaches, then fall once it passes. You're hearing the "Doppler effect".

Image Source: http://www.geography.hunter.cuny.edu

Note that the waves with the peaks closer together have higher frequency, and the further apart flatter ones have lower frequency.

Like sound waves, radio waves have a certain frequency, the number of oscillations per unit of time. When the radar gun and the tennis ball are both standing still, the echo will have the same wave frequency as the original signal. Each part of the signal is reflected when it reaches the tennis ball, mirroring the original signal exactly.

But when the ball is moving, each part of the radio signal is reflected at a different point in space, which changes the wave pattern. When the ball is moving away from the radar gun, the second segment of the signal has to travel a greater distance to reach the ball than the first segment of the signal.
This has the effect of "stretching out" or "flattenning out" the wave, or lowering its frequency. Based on how much the frequency changes, a radar gun can calculate how quickly the ball is moving away from it.

Okay, so how does the Radar measure the ball speed and ignore the speed of the player's arm moving?

Most radars detect the speed of the strongest return target and the speed of the fastest target. The strongest
return is usually from the nearest object, (like the player), and this speed is lower, and slows down much quicker than the ball speed. So it is very basic Maths to select the higher and longer lasting speed of the ball.

Anyway, thanks to electronics and computers to cheaply do the Mathematics, we can even buy "toy" radar guns for our kids. They can use them to measure speeds of bikes and skateboards going down big hills and the like.

Image Source: http://www.hothardware.com

Movement Detection by Digital Cameras

There is also some amazing movement detection technology that is inside digital cameras these days.

I recently purchased a Panasonic Lumix ZS3 12x fully automatic 10MP Digital Camera. There are many special modes that the camera can be set to, including "Sports Mode". I have been very impressed with the quality of the pictures taken in sports mode. The camera is able to follow the action and stay in perfect focus without any of the blurring that I used to get with my old camera. There is also no need to use a tripod when at full zoom in this mode. The shake correction is absolutely brilliant. Watch out for an upcoming post that gives a full review of this marvelous camera.

Slide Show of Australian Open Photos

I have been very impressed with the Wonderhare Photo Gallery Maker
- See previous post on this at:

http://passyworldofict.blogspot.com/2010/01/wondershare-photo-gallery.html

So combining the new camera and Wondershare, here is a slideshow of photos that Big Passy took as a special guest at the Australian Open Tennis.

Note that several photos have been cropped, and had the image contrast, brightness, and so on, auto adjusted using Adobe Photoshop CS3. Photoshop is brilliant for adding some Gaussian Blur to unwanted background items as well.

(You should have noticed a little bit of Photoshopping on the intro photo.
Eg. "Passy World" is not an official sponsor of the Australian Open).

And before we get another influx of emails about sexist content, let
me just clarify that the matches BPW attended were the "Ladies Qualifying Matches".
No men were playing, and hence no pictures of men were taken!

(Push the Play button arrow below if the slideshow is not already running).

If you would like to see the above slideshow full size, then click on this link: http://www.passyworld.com/passyHTMLs/TennisPhotos1.html

If you would like to get your own copy of "Wondershare Flash Gallery Factory Deluxe" (for just under \$50 US) then click the following link:
http://www.flash-gallery-software.com/purchase-flash-gallery.html

So that's another marvelous blog post served up,

Enjoy,
Big Passy Wasabi

#### 1 comment:

1. Hey........

Thanks a lot for sharing a good article....

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