Ordnance Survey staff have mapped the Queensferry Crossing to an incredible 2cm accuracy – but have only set foot on the bridge once.
A team from the United Kingdom’s mapping agency have tracked every change to the new structure and its surrounding road lay-out for the last four years.
They have provided a detailed picture of the huge project site – which stretches from the M9 to Dunfermline.
The information is used in electronic format by organisations such as emergency services, local authorities and developers, along with sat nav and internet firms like Google Maps.
The surveyors use portable hi-tech equipment to produce maps which are the envy of the world for their accuracy and clarity.
These include a global navigation satellite system, which looks like a dish on a pole, that picks up information from both United States and Russian satellite networks.
Its data is transferred remotely by Bluetooth to a rugged tablet computer, or “tough book”.
Further detail is recorded using a theodolite, which measures angles and distances.
Most of the bridge information going into the maps is gathered from vantage points such as the foreshore in North Queensferry, where staff spent several days last week finishing what has been one of their biggest Scottish projects.
The staff have only needed to go on to the bridge to check intricate details, such the shape of its tapered towers at road level because this are not visible from afar.
Ordnance Survey production manager Scotland Derek Smith, working with geographical information system surveyor Guy Rodger, explained why they measured to such a scale.
He said: “I’m sure the bridge has been built exactly as specified, but that’s not the case with every house. The information we produce will be useful to someone.”
For the public, the bridge is already shown in the relaunched Ordnance Survey Road series of green-cover maps for motorists, albeit at a small 1:250,000 scale, or 1cm per 2.5km.
A new edition of the popular pink-cover Landranger series with the bridge included – far more detailed at 1:50,000 scale – is due to be published shortly.