Between March and October each year the Ordnance Survey creates millions of aerial image files which are used to produce the overall digital picture of Great Britain. The size of a typical raw file is up to 700MB, while the edited files are at least 90MB. The raw data is also being kept for posterity as a digital archive of the land.

Dave Lipsey, information systems infrastructure manager, says the data will be even more important 50 or more years from now.

‘The project to digitally map Great Britain presents us with a storage challenge that requires us to access terabytes of data far into the future,’ he says.

‘Working files need to be backed up and all our digital imagery has to be securely archived because we may need to go back to it in many years’ time.’

Production data is backed up to tape and optical media is used to store and provide a backup copy of archived data. Most of the production systems are backed up using Veritas NetBackup and LTO tape, although Lipsey says that this medium is not resilient enough.

‘For long-term storage we use an archiving system from BridgeHead that can handle the addition of multiple terabytes each week, and Plasmon’s Ultra Density Optical media with a life expectancy of 50 years,’ he says.

‘Without that, the aerial images digital capture project would be impossible to manage.’