They know where you are through your mobile

Your neighbours could be watching you - via a spy satellite which will take detailed pictures to order over the Internet. Meanwhile, Big Brother can track you by your mobile phone. Is this progress welcome? Charles Arthur, Science Editor, explains that whether you like it or not, it's here.

Within the next few days, Internet users will be able to order photographs showing their house and its environs to a resolution of 10ft, using pictures taken to order from an orbiting satellite - just the ticket for those arguing boundary disputes.

Meanwhile, the security services could be tracking your movements around the country by the signals emitted from your mobile phone while it is turned on - even if you are not using it for a call.

The arrival of the personalised spy in the sky comes through an American company called Earthwatch, based in Longmont, Colorado. Its Earlybird- 1 satellite was launched from Russia and just before Christmas was successfully put into orbit, 295 miles above Earth. It orbits about once an hour, adding pictures to a vast database that the company is building up to create a "digital globe".

Earlybird can take pictures in which each frame covers an area of 3.5 square miles (9 sq km), and each pixel, or grain, in the picture is 10ft (3m) in size. By taking closely-matched pairs of frames, three-dimensional pictures can be built up. That, though, will be superseded late in 1998, when Earthwatch is launching its Quickbird-1 satellite. It will be able to distinguish objects 3ft across - detailed enough to see a paddling pool.

Spy satellites in the past had similar capabilities; despite the tales, a satellite could never read the headlines in a newspaper in Red Square. But this technology has only recently been declassified by the US military - giving American industries a huge head start in the commercial imaging market.

"Ours is the highest-resolution satellite imagery available from a commercial source. The people of the world will soon have easy and inexpensive access to the most refined representation of our planet ever assembled," said Donovan Hicks, head of Earthwatch. "This launch also shows what can be accomplished when we pool our global technological resources, and is a vivid reminder that the Cold War is over."

Not entirely: the pictures are available to anyone, including governments - except those of Cuba, Iran, Iraq, Libya and North Korea. But pictures of those countries will be added to the company database.

The resolution available brings satellite imagery into the hands of anyone prepared to pay at least pounds 200, with the images costing about pounds 1.80 per sq ft. If the company has not already taken a picture of the required area, you can order it yourself and it will be taken on the next suitable orbit.

Combined with details from mobile phones, this could allow Big Brother to know what you are doing, and trace you, throughout the day. British mobile phone companies have revealed that when required to by court order, they will allow the law enforcement agencies access to their computer data.

This means that someone whose phone is switched on can be tracked around the country, because the phone emits a signal to keep in touch with its nearest "base station" every 30 minutes. That can also provide evidence, which can be used in court, of a person's whereabouts in criminal cases.

For those who have their phones constantly switched on - as terrorists or criminals are assumed to - it is akin to having a homing device in your pocket.