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Pool Watch
? ?Swimmers can
drown in busy swimming pools when lifeguards(救生员) fail to notice that they are
in trouble. The Royal Society for the Prevention of Accidents says that on
average 15 people drown in British pools each year, but more suffer major injury
after getting into difficulties. Now a French company has developed an
artificial intelligence system called Poseidon that sounds the alarm when it
sees someone in danger of drowning.
? ?When a swimmer sinks
towards the bottom of the pool, the new system sends an alarm signal to a
poolside(游泳池边) monitoring station and a lifeguard’s pager. In trials(试验)at a
pool in Ancenis, near Nantes, it saved a life within just a few months, says
Alistair McQuade, a spokesman for its maker, Poseidon Technologies.
?
?Poseidon keeps watch through a network of underwater and overheard video
cameras. AI software analyses the images to work out swimmers trajectories(轨道).
To do this reliably, it has to tell the difference between a swimmer and the
shadow of someone being cast onto the bottom or side of the pool. "The
underwater environment. Is a very dynamic one, with many shadows and reflections
dancing around, " says McQuade.
? ?The software does this by
"projecting" a shape in its field of view onto an image of the far wall of the
pool. It does the same with an image from another camera viewing the shape from
a different angle. If the two projections are in the same position, the shape is
identified as a shadow and is ignored. But if they are different, the shape is a
swimmer and so the system follows its trajectory.
? ?"To pick out
potential drowning victims, anyone in the water who starts to descend slowly is
added to the software’s "pre-alert" list," says McQuade. Swimmers who then stay
immobile on the pool bottom for 5 seconds or more are
considered in danger of drowning. Poseidon
double-cheeks that the image really is of a swimmer, not a shadow, by seeing
whether it obscures the pool’s floor texture when viewed from overhead (在头顶上).
If so, it alerts the lifeguard, showing the swimmer’s location on a poolside
screen.
? ?The first full-scale Poseidon system will be officially
opened next week at a pool in High Wycombe, Buckinghamshire. One man who is
impressed with the idea is Travor Baylis, inventor of the clockwork(时钟机构) radio.
Baylis runs a company that installs swimming pools — and he was once an
underwater escapologist (表演脱身术的人) with a circus. "I say full marks to them if
this works and can save lives, " he says. But he adds that any local authority
spending ￡30,000-plus on a Poseidon system ought to be investing similar amounts
in teaching children to swim. |
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