The Republic hasn't got an orbiting satellite but that doesn't stop us having access to the data these spacecraft provide. An Irish company has been processing, refining and interpreting satellite data here for the past 16 years.

Department of Geology specialists at Trinity College, Dublin, established ERA-Maptec in 1984 explained co-founder, Dr Martin Critchley. "It was started as a company at Trinity, it was the first campus company," he explained. "It arose out of EU research we had looking at mineral deposits in the Irish midlands."

The team was researching ways to process satellite data for mineral exploration, explained Dr Critchley, who is the company's remote sensing and GIS (geographical information systems) manager. This expertise grew into consultancy and eventually a standalone company.

This research activity continues at ERA-Maptec, he said. "We are using two main technologies, image processing, which allows us to manipulate the image and extract information from the image," Dr Critchley stated. The second is GIS, which he described as "a sophisticated mapmaking technology".

Satellite imaging technology for most people usually conjures up the notion of a "spy in the sky" and in fact this was one of the main reasons for the deployment of these satellites. The key issue in their development was how sharply you could see the ground assuming an orbital distance for the satellite of 100 miles or more, a factor known as resolution.

The best imaging satellites were reserved by the military and these were reputed to be able to read the licence plate of a vehicle, although Dr Critchley believes this is a bit fanciful. "It is rumoured that you can get data to "a resolution of 20 cm", he said. The military also uses radar satellites which could "see" at night and through clouds.

The US military had a powerful say over the release of satellite data for many years, he said. "Up until about two years ago there was a US limit to the resolution you could sell to civilians."

This embargo on the data has been lifted, however, and this has changed the access available to specialist companies such as ERA-Maptec.

Before the embargo was lifted, data from the US Geological Survey, the French SPOT satellite and Landsat could deliver a resolution of between four and five metres. In other words, objects had to be at least this size before they could be identified with confidence.

Last March, however, ERAMaptec announced it had become the local agent for data from the IKONOS satellite, launched in September 1999 and operated by Space Imaging Europe. IKONOS brings the resolution down to one metre. Details such as individual trees and bushes, cars and even groups of people can be seen at this resolution.

The company takes the raw satellite data and uses a range of technologies to process it for its clients. The price is usually calculated on the basis of area covered and while it would be possible to ask for a shot of your back garden there was a significant cost involved, Dr Critchley said. While your home and its immediate neighbourhood might only amount to $20 (€22) or $30 a minimum purchase of $3,000 applied to any contract.

The new high resolution images would open up new markets for the company, he believed, particularly where aerial photography might have been used in the past. The data can be processed and used to update road maps, survey topography for land development or be used to measure soil erosion along our coasts. The satellite can measure vertical heights to a precision of one to two metres and this could be used in urban planning or construction.

ERA-Maptec won an EU contract which compared Dublin's built environment as it is now with how it was 40 years ago and this was completed 12 months ago, Dr Critchley said. It showed how surrounding land had disappeared under housing and how commercial development had grown.

Satellite data could also be used to study crops and vegetation cover, he said. A lower resolution is used and colour information coming from the ground is analysed and this could be used to monitor how farmers were applying set aside and Rural Environment Protection related programmes.

The data could highlight overgrazing of mountains by sheep, measure root crops versus cereal crops or barley cover versus wheat.

The Department of Agriculture was also involved in a project to map every field border in the State using satellite data, he added.

The company's latest research involved applying computer-based artificial intelligence to help interpret satellite data.

It was "getting more difficult for human operators" to do this consistently and objectively he, said.

The GIS aspects were also being developed for land use studies but also the application which helped found the company, mineral exploration and geological studies.