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The
Coming
Revolution
in Sport?
I
f you’ve been watching the cricket
or tennis on TV this summer, you’ll
no doubt have seen (and heard
of) Hawk-Eye. Just how does this allseeing, all-knowing electronic “eye”
do its thing?
For those who have been too absorbed in the 20th movie repeats of the
summer to watch live sport, perhaps
a word or two of explanation: HawkEye is an electronic umpire, able to
tell (for example) whether a Brett Lee
screamer would have hit the stumps
had it not hit the pads of a hapless
batsman. Or whether a Roger Federer
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190km/h serve did clip the line, regardless of the fact that the linesman
called it out.
Hawk-Eye is of course capable of
a whole lot more, as we will shortly
see – but you get the picture.
by Ross Tester
It is the brainchild of Dr Paul
Hawkins, a 29-year-old PhD who
developed the unique system for his
employer, Roke Manor Research (itself a division of Siemens), in Romsey,
Hampshire, England.
In a nutshell, Hawkins took the
extensive research which went into
Roke’s military tracking system (the
single-camera RAPiD system, a model
based tracking system which was born
out of developments in civil robotics)
and applied it to the 3-D, multi-camera
world of tracking a ball in flight. Interestingly, Roke developed the military
tracking system to track missile trajectories and therefore targets during
the Gulf War.
Due to Hawkins’ interest in cricket
(he’s a social player), Hawk-Eye was
March 2004 7
In the cricket version,
Hawk-Eye uses six fixed video
cameras placed around the
edge of the arena. The images
are electronically compared
and analysed to determine
the ball’s location at any
instant. A somewhat similar
arrangement is used for
tennis.
first developed for the cricket pitch.
Since then, it has been developed for
tennis, baseball and even snooker/
pool. The name, by the way, is Paul
Hawkins’ father’s nickname – and it
also very aptly sums up the system
itself!
Hawk-Eye was launched in 2001
and in that year won the Royal Television Society award for Technical
Innovation.
Why use Hawk-Eye?
There are few more frustrating
things to a sportsman or woman (and
therefore to millions of fans) than a
“bad call” by a judge, umpire or other
official. Worse is when that bad call
has a major influence on the outcome
of the game.
The problem is, of course, that many
of the decisions officials have to make
are for events which last no longer than
the blink of an eye. In many respects,
it’s a wonder that officials do manage
to get it right most of the time. And
believe it or not, they do.
Take cricket, for example. A lot of
umpiring decisions are relatively easy:
that delicious sound (for a fast bowler!)
of leather crashing into the stumps and
the sight of the bails flying high in the
air! Catches are usually fairly simple,
too – although umpires these days may
call on the “third umpire” with the
benefit of slow-motion replays if there
is any doubt, either if a ball has carried or if it even hit the bat. Likewise,
run-out decisions are often assisted
by electronic means if the umpire is
in any doubt.
Somewhat surprisingly, about the
only ruling that isn’t currently electronically assisted is LBW (leg before
wicket). We say surprisingly because
it is in LBWs that electronic assistance
is arguably – with Hawk-Eye – now the
most certain.
And it is LBW decisions that
are usually the most controversial,
because they involve a “what if”
judgement, as distinct from an event
judgement. The umpire must decide
not only if the ball was travelling at
such an angle and height that it would
have hit the stumps were the pads
not hit first; he must also judge that
the ball also ptched inside the line
of leg stump. And if the batsman had
advanced down the wicket, it becomes
that much harder.
Now put the speed of the ball into
the equation: perhaps 150km/h or so
and you’ll see why errors do occur. In
fact, in the first season that Hawk-Eye
was used as an aid to commentators, it
indicated that 13 out of 21 LBW decisions were wrong – both ways.
Although initially designed to be
used in television coverage, the system
could also be used by the umpires to
bring a measure of consistency into the
decisions being made during a match.
The final decision on LBW will always
be with the umpire but Hawk-Eye
would add significant value by making precise measurements which the
human finds very difficult.
Perhaps we are getting ahead of ourselves. Hawk-Eye has not (yet!) been
used by umpires to assist in their decisions as to whether or not a batsman
is out. However, that day must surely
come as TV networks not only bring
the umpire’s calls into question with
endless slow-motion replays – now
with Hawk-Eye simulations they can
prove, with virtually no error, whether
the umpire was correct or not.
It will arguably be the public who
force the issue eventually, as there is
little call from umpires to have the
extra technology at their fingertips.
This is one of the features of HawkEye – its data can be almost instantly
transmitted to the man in the middle
to help with difficult decisions.
Using a small hand-held computer
or PDA, the umpire can tell straight
away whether a batsman should have
been out.
Just some of Hawk-Eye’s seemingly endless possibilities for giving the viewer added enjoyment in a match. The first screen
shows the ball trajectory from the moment it left the bowler’s hand; the second the point of impact with the bat (or body!)
8 Silicon Chip
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Similarly, tennis umpires could
have the technology at their disposal
for dubious line calls. How many
matches have swung one way or the
other following an obvious (to the
TV viewer!) mistake. They break the
player’s concentration at the very least.
Not everyone agrees . . .
There has been some reaction from
players – both positive and negative,
as you might expect. A batsman who
has been on the wrong end of too
many LBWs is much more likely to
favour the system than one who has
“gotten away with murder” out in
the middle.
Even former cricket “greats” are
divided. A newspaper column written by the former fast bowler Dennis
Lillee dismissed Hawk-Eye almost out
of hand. But Paul Hawkins claimed
that article was “probably the most
ill-informed ever written about the
system . . .”
Dickie Bird, the former UK umpire,
was once a critic but is now one of
Hawk-Eye’s biggest supporters. He
originally claimed that it would kill
the game but now advocates its use.
“Surely the need is to alleviate error,”
he said.
Similarly, tennis authorities such as
the ITF have not yet given Hawk-Eye
their glowing endorsement, citing cost
as one reason.
However, John McEnroe, commentating during the Australian Open finals, glowingly praised Hawk-Eye and
wished it was available to the umpire
after a couple of obvious errors in line
calls. He even joked with the other
commentators when one remarked
that it would have put an end to his
now famous (infamous?) “You cannot
be serious!” arguments with tennis
umpires and referees.
Another claim from sports administrators is that Hawk-Eye could be
seen to undermine the authority (and
skill levels?) of the officials around
the court.
They are not unique: most sports
over the years have been reluctant to
adopt new technology to assist their
officials. Having seen this first-hand
in other sports, where electronics is
allowed to overrule course judges, all
I can say is bring it on . . .
How Hawk-Eye works.
The Hawk-Eye system tracks the ball
from the moment it leaves the bowler’s
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Hawk-Eye can
superimpose
the batsman in
typical stance to
show just where
the balls faced
have actually
ended up. It’s
valuable for
later review of
performance and
also for coaching.
hand until it stops (or of course from
the tennis racket). It does this using
both image analysis and radar technology. If required, it then projects the
flight of the ball after it has stopped,
by extrapolation.
Using dedicated cameras and specialist image processing software, the
position of the ball can be located
extremely accurately in three dimensions.
On the cricket ground, six fixed
and synchronised “JAI” monochrome
cameras, with a 120Hz frame rate, are
placed around the perimeter of the
playing field at specific points – two
are 30° off each end of the wicket
while two side cameras look directly
across their respective stumps. These
synchronised cameras track the ball’s
entire trajectory – at intervals of
1/120th of a second – from the moment it leaves the bowler’s hand until
it stops.
The six cameras are gen-locked into
two sets of three cameras, each set being captured by a Matrox Meteor-II/
Multi-Channel frame grabber and the
Matrox Imaging Library (MIL-Lite)
software.
The resulting images are processed
into a 3D image by the Hawk-Eye system which then calculates – in a split
second – where the ball pitched, the
extent of its lateral movement in the
air and off the wicket, its velocity and
bounce and – if applicable – exactly
where it contacted the batsman’s pad.
Positional accuracy is claimed to be
no worse than five millimetres, with
some references giving Hawk-Eye an
accuracy of 1-2mm (assuming fixed
camera positions).
The future path of the ball is also
extrapolated by fitting the trajectory
of the ball into a parametric model,
thereby determining whether or not
the ball would have carried on to hit
the stumps, bounce over, or go past
the wicket. Hawk-Eye then uses a
Matrox Orion frame grabber to overlay a graphical representation of this
trajectory onto a video image.
This image is then encoded and
transmitted to a video bank, ready
to be virtually instantly accessed by
television production staff and commentators.
Tennis uses a similar process to
cricket – Hawk-Eye is most useful for
determining when a ball is in or out.
But for the TV audiences, it has been
extensively used to show the action
of, for example, a serve and just how
far the balls swing.
A market is also seen for Hawk-Eye
in coaching – stroke analysis is easy
when you can show exactly what
the ball does. The South Africans
have been using Hawk-Eye for this
purpose and last October, the system
was installed at the English Academy
at Loughborough College, near Nottingham.
Not only cricket and tennis
In partnership with Sunset + Vine,
the television production company,
Roke Manor Research has established
Hawk-Eye Innovations Ltd, an organization entirely dedicated to the
development of similar technologies
for wider sporting activities and applications. Dr Hawkins is its CEO.
So far, Hawk-Eye has been adapted
to baseball – primarily to determine
strikes and balls – and is also available
for football (particularly gridiron) and
even snooker/billiards/pool!
SC
Acknowledgement:
Much of the information and text for
this article originally came from Roke
Manor Research and Matrox. Hawk-Eye
screen diagrams courtesy of Channel
9, Sydney.
March 2004 9
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