Image caption The DMC-3 satellites will see details less than a metre across

Chinese and UK companies have agreed a deal that will result in three high-resolution Earth observation spacecraft being built to map China's extraordinary growth from orbit.

The deal was penned between Guildford satellite imagery provider DMCii and Beijing-based company 21AT.

It means DMCii can now roll out its new constellation of spacecraft that will picture details on the surface of the planet less than a metre wide.

They should be ready to launch in 2014.

For 21AT (Twenty First Century Aerospace Technology Company Ltd), it means it can have ready access to Earth imagery without the worry of having to launch and operate satellites in orbit.

The Chinese company will take 100% of the capacity of the three spacecraft over an initial contract period of seven years. Day-to-day use of the data will be handled by 21AT subsidiary, BLMIT.

It will use the pictures to monitor land use and land-cover changes. In particular, the data will enable regional governments to plan better the extraordinary rate of development in China's cities.

The satellites for the DMC-3 constellation, as it is called, will be manufactured by DMCii's parent company, Surrey Satellite Technology Limited (SSTL). It will cost some £110m to build, launch and insure these platforms.

Image caption The imagery from the satellites will be needed in particular for urban planning

Approval for the deal has come from the highest levels in government in both London and Beijing, and the satellite data package was actually part of the £1.4bn of trade agreements signed between premiers David Cameron and Wen Jiabao during their summit on Monday.

Both administrations gave their consent after being re-assured that no technology transfer rules were being broken.

The DMC-3 constellation will be operated on a different business model to the other satellites managed currently by DMCii.

These older platforms are wholly owned by the countries that use their data. In the case of DMC-3, the Guildford company will own the spacecraft and lease the capacity to the Chinese. It is a model familiar in satellite telecommunications but not in Earth observation.

Each DMC-3 satellite will be in a larger class than the earlier spacecraft - about 350kg in mass.

As well as their high resolution cameras (1m/pixel resolution panchromatic; 4m/pixel resolution colour), they will also accommodate imagers capable of mapping ultra-wide strips of the Earth's surface, albeit at resolutions above 20m.

This broad-swath facility will allow DMCii to use the new satellites for disaster response - a key skill the company has developed for itself during its seven years of existence.

Its current fleet plays a leading role in acquiring the urgent maps needed by relief agencies when a natural or man-made calamity strikes a particular corner of the globe.

Image caption The deal was signed on Monday - part of a much wider UK-China trade agreement

No formal arrangement has been put in place to allow the Chinese-sponsored platforms to perform this function, but it is expected they will take up some humanitarian duties from time to time.

21AT-BLMIT already does this with the Beijing-1 satellite that has been managed in orbit by DMCii since its launch in 2005. Beijing-1 returned much needed imagery following the Wenchuan earthquake in 2008.

The vast majority of the time, however, the DMC-3 satellites will be busy mapping the rapidly changing landscape of China. Their coverage should ensure that any given area in the country can be re-visited on a daily basis.

DMCii hopes the initial three satellites can be followed by a fourth in due course.

"There is an enormous requirement for Earth observation data in China - for urban planning, for agriculture and water management, everything - and they also want to be able to update everything rapidly," explained SSTL Chairman, Sir Martin Sweeting.

"On that basis we planned to put up a constellation of three spacecraft, but when the Chinese went away and looked in detail at what they needed they realised they wanted all the data. So, we'll launch these first three satellites and then look at putting up a fourth to expand the capacity and bring other partners on board as well," he told BBC News.

Jonathan.Amos-INTERNET@bbc.co.uk