快猫短视频

THE KIDS are going to love this. You walk up to the teacher鈥檚 desk with a
little practical joke in mind. Your mobile phone suddenly bleeps, and you hear a
soft whisper in your ear: 鈥淢AJOR bad mood today鈥攄on鈥檛 try anything.鈥� You
think better of the prank and decide to avoid certain detention. All thanks to
an invisible message placed in the air above the teacher鈥檚 desk.

But this will be more than a plaything. Drivers involved in an accident will
post a message in the air over the scene so that in-car satellite navigation
systems can warn other motorists to steer clear of the area. Sailors could warn
each other of shifting sandbanks that might ground an unsuspecting ship. And
food-lovers could post messages outside a restaurant door, giving subsequent
visitors an instant endorsement鈥攐r a warning to take their custom
elsewhere.

Pinning messages in mid-air, using the location鈥檚 Global Positioning System
(GPS) reference, could become the next craze in communications. The messages are
not actually kept in the air: they鈥檙e stored on an Internet page. But that
page鈥檚 Web address is linked to coordinates on the Earth鈥檚 surface, rather than
a person or organisation. As you move about, a GPS receiver in your mobile phone
or PDA will check to see if a message has been posted on the website for that
particular spot. If you鈥檙e in luck a snippet of info鈥攍eft as text or a
voice recording by someone who passed there previously鈥攚ill pop up on your
screen or be whispered into your earpiece.

This is all made possible thanks to the current proliferation of GPS receiver
systems that can pinpoint your position on the Earth鈥檚 surface鈥攊ncluding
your altitude鈥攖o within six metres. They rely on a network of 24
satellites that broadcast radio signals down to the Earth. Depending on your
location, you鈥檒l receive the signals from different satellites at different
times. So comparing the arrival times of signals from each one allows the
receiver to calculate your location.

A typical GPS receiver now costs only $100 compared to $100,000
a decade ago. And it has shrunk too, to the size of a dime instead of a
suitcase, which means one can be embedded in a phone, a wristwatch or the hem of
a jacket. Although many cars now come with a GPS locator as standard, they are
still a rarity in phones鈥攂ut that鈥檚 about to change. All cellphones made
in the US now have to include some form of locator technology so that they can
be tracked by emergency services. European manufacturers are discussing a
similar move. And when everyone is carrying locators around with them, we can
all begin to hang messages in mid-air. 鈥淥nce you鈥檝e got widespread GPS
capability, you鈥檝e pretty much got what you need,鈥� says Blair MacIntyre of
Georgia Institute of Technology鈥檚 College of Computing.

One of the biggest schemes to exploit GPS messaging comes from
Hewlett-Packard. It began as a typically Californian idea: what if everything
had its own Web page? A washing machine鈥檚 page would tell the engineer who comes
to fix it everything about its service history. A valuable painting could have a
page detailing its provenance.

And so, in 1994, HP engineers in Palo Alto started to create this new
environment, calling it CoolTown. They began by assigning Web addresses, in the
form of bar codes, to VCRs, hot tubs and鈥攑erhaps more
usefully鈥攎edical equipment. A mobile phone or PDA with a bar-code reader
would simply scan the object鈥檚 code to download any relevant information. Later
versions replaced the bar code with beacons鈥攖iny transmitters broadcasting
the Web address encoded in radio waves.

CoolTown is now a joint venture between HP鈥檚 labs in Palo Alto and Bristol.
The idea of giving every bit of empty space its own Web page only came last
year, when Bristol University student Alistair Mann came to HP to work on his
master鈥檚 degree project. Mann had been part of a team experimenting with a
鈥渃yberjacket鈥� connected to the Internet by a mobile phone hidden in a sleeve.
When it received text messages, a text-to-speech synthesiser played them into an
earpiece. The jacket also sported a GPS locator.

Mann knew researchers at Lancaster University had whipped up a similar
garment for tourists: a server would use locator beacons, scattered around the
environment, to beam relevant messages to the jacket about historical sites,
restaurants and other attractions to tempt visitors in the neighbourhood. 鈥淚
realised that we could put the technologies of GPS and the cyberjacket
together,鈥� Mann says. GPS means that you could attach digital media such as
e-mails, text messages and Web pages to a physical position.

HP now has a prototype mid-air messaging system running in its Bristol lab.
The researchers leave each other notes around the building, even if they just
announce trivial things like 鈥済one to get some coffee鈥�. This enables the
company鈥檚 engineers and executives to explore the system鈥檚 strengths, weaknesses
and potential uses.

For now, the largest obstacle to the widespread use of mid-air messaging
isn鈥檛 one that the researchers can engineer their way around. 鈥淚t depends quite
considerably on the quality and availability of wireless connectivity,鈥� says
Simon Crouch, head of the CoolTown messaging project at HP鈥檚 Bristol labs. About
60 per cent of Europe鈥檚 population already lives within range of a mobile phone
transmitter. There will soon be a few 鈥渉ot spots鈥� with good quality high-speed
wireless access, Crouch says, but it鈥檚 going to be five years or more before
that kind of connectivity is pervasive.

However, that will allow time for GPS to come of age. GPS receivers don鈥檛 yet
work well indoors where electrical wiring and other noise can interfere with
their faint signals. But GPS will be more powerful in its next incarnation, with
indoor booster stations in many office buildings, car parks and other public
places. And a new satellite system, due for launch in 2005, will allow anyone,
anywhere to pinpoint their location to within 3 metres.

For many businesses, it will be a marketing dream come true. Retailers will
be falling over themselves to bombard people passing their doors with targeted
come-ons (or, in this case, come-ins). But it will also work the other way
round, enabling you to find what you want. Software from California鈥檚 directory
service go2.com, for example, can already enable your mobile phone or PDA to
locate a universe of services, including the nearest store selling Coca-Cola,
computer classes, flats to let or local firms hiring people in your line of
work. Visitors might simply want to find out about nearby restaurants.

But the prospect of every place on Earth being crammed with invisible
electronic notes, questions and suggestions (and maybe even graffiti) conjures
the spectre of an information traffic jam as big as cyberspace itself: what
happens if 10 million people are using all of these devices in the same country
at the same time? Crouch isn鈥檛 unduly worried. There are open questions about
scaling up the prototype systems, he admits, but the new messaging technology is
grounded in current Web technology. It creates no new problems, it just taps
into the old questions of how to design and manage a growing infrastructure for
the Web. It is largely a question of managing hardware and being very careful
about balancing loads between servers. 鈥淚t鈥檚 a challenge, but it all seems
feasible,鈥� Crouch says.

A universal open messaging system also raises questions about privacy and the
reliability of information. Unscrupulous merchants may attach scurrilous
messages about their competitors to those businesses鈥� GPS coordinates. Perhaps
the glowing review that lured you to Chung鈥檚 Chinese Kitchen was planted by
Chung himself. Crouch and his colleagues are well aware of this problem and say
the prototypes they are running will help them deal with the problems of privacy
and security.

There are some very simple mechanisms that can restrict who gets to post you
a message, and who gets to read the ones you write, they say. You could, for
instance, join a paid service that would scrutinise messages and guarantee their
authenticity and usefulness. Crouch and Mann envision people embedding their
devices with personal profiles designed to screen out prying eyes or specific
kinds of messages, only allowing acceptable people and businesses into their
personal space. 鈥淚f you use a system in which GPS determines your location, you
own the information about your location,鈥� Crouch says. That means you can refuse
to release your exact coordinates, or only let particular kinds of services see
you.

None of the potential difficulties have so far dampened Crouch鈥檚 enthusiasm.
鈥淲e believe that the attractive features outweigh the drawbacks,鈥� he says.
鈥淭hat鈥檚 what drives us.鈥� The Bristol team believe mid-air messaging could be a
real money-spinner鈥攂ut there is one hitch. They鈥檙e not yet sure exactly
what it might be used for. 鈥淢uch of the success of this kind of system will
depend on developers coming up with things that are useful,鈥� Crouch says. HP鈥檚
developers haven鈥檛 actually pinned down all of the things we might do with
mid-air messaging鈥攊n fact, the company is actively seeking inspiration. It
has posted a free software developer鈥檚 kit on its website so that potential
users can play around with the system, and it is recruiting developers to come
up with new applications. So, here鈥檚 your chance to shape the future of
communications. Got any bright ideas hanging in the air above your head?