more Lidar data, meaning more discoveries are likely in the coming years as

Some parts of the road are concealed, while others are easily visible

Seven have been found in two years,

They have been lost for thousands of years, but now a 'revolutionary' technique involving lasers is shedding lights on Roman roads and forts.

Archaeologists are using Lidar (light detection and ranging) data - which is typically used for flood modelling - to pinpoint the location of hundreds of miles of Roman roads in the north of England.

Their discoveries are giving clues to a neglected chapter in the history of Roman Britain almost 2,000 years ago when these roads helped Rome's legions conquer and control northern England.

Archaeologists are using Lidar (light detection and ranging) data - typically used for flood modelling and tracking changing coastlines - to pinpoint the location of hundreds of miles of Roman roads in the north of England. This image shows Vindolanda Roman fort in the centre, identified using Lidar data

For decades after the 43AD Roman invasion of Britain, a large region of the North, including what is now Lancashire, Yorkshire and Cumbria, was controlled by a Celtic tribe known as the Brigantes.

Roman writer Tacitus wrote it was the collapse of the marriage between Queen Cartimandua of the Brigantes - a Roman ally and her husband Venetius - that led to a showdown with Rome.

Following their divorce, Venetius organised a revolt in 69AD and Cartimandua fled.

The Emperor Vespasian then sent a force under Britain's new governor, Quintus Petilius Cerialis, to put down the rebellion and conquer northern England.

Building roads to link up forts and settlements across this rugged landscape was a vital part of this decades-long conquest of the North.

Amateur archaeologists have been able to use the flood maps, produced by the Environment Agency, to discover seven roads in the UK since 2013. The most recent connects Ribchester and Lancaster (shown)

Environment Agency Lidar data played a vital role in the search for Lancashire's lost Roman roads. This map helped to reveal part of the road from Ribchester to Catterall

THE ROADS USED BY THE ROMANS For decades after the 43AD Roman invasion of Britain, a large region of the North, including what is now Lancashire, Yorkshire and Cumbria, was controlled by a Celtic tribe known as the Brigantes. Roman writer Tacitus wrote it was the collapse of the marriage between Queen Cartimandua of the Brigantes - a Roman ally and her husband Venetius - that led to a showdown with Rome. Following their divorce, Venetius organised a revolt in 69AD and Cartimandua fled. The Emperor Vespasian then sent a force under Britain's new governor, Quintus Petilius Cerialis, to put down the rebellion and conquer northern England. Building roads to link up forts and settlements across this rugged landscape was a vital part of this decades-long conquest of the North. Advertisement

Archaeologists have used Environment Agency Lidar data to find seven of these important routes in two years.

Maps were created by aircraft equipped with laser scanners, which measure the distance between the aircraft and the ground.

The precision technology can detect differences in the height of the land of as little as 2-inches (5cm), making it ideal for detecting hidden structures buried under the soil.

Although the Environment Agency has been using the technology for some 20 years, it only made its Lidar maps available to the public in 2013.

Amateur archaeologist and retired road engineer David Ratledge,70, who has been researching Roman roads in Lancashire for 45 years, has used Lidar data to find an 11-mile (17km) long road between Ribchester and Lancaster.

He told The Times it is the first 'new' Roman road to be discovered in the UK for 150 years.

'These were the county's most important Roman sites so good communications between them must have been essential,' he said.

'Previously in Lancashire we only had aerial photographs from the 1940s and 1960s to go on, but with photographs, features only show up after a drought and we don't get many of those.'

Often Roman roads are very hard to spot from clues on the ground. These annotated photos along the route from Ribchester to Catterall show how hard it can be without Lidar to lead the way

'With Lidar, once you know what to look for, it's blindingly obvious - you just know you've found a road...It's been revolutionary.'

ROMAN ROADS IN BRIEF Roman roads were large structures, typically measuring 16 to 23ft (five to seven metres) wide. They reached a height of around one-and-a-half feet (half a metre) in the centre. While the Romans were famous for building roads in straight lines, the discovery of a road between Ribchester and Lancaster shows they also took the natural geography of a place into account, to avoid steep hills, for example. The roads were used to transport goods efficiently and for marching soldiers. Preservation of Roman roads in the UK varies, with some still protruding from the land and easily visible. Others are hidden under earth and have only been found thanks to Lidar. Advertisement

Although it was well known that there was a Roman road linking Ribchester to Lancaster, archaeologists spent decades searching for it in the wrong place.

They based their area of focus on the fact that Romans tended to take the shortest and most efficient route from place to place – and assumed that the road would run from northwest Ribchester in a straight line to Lancaster.

In reality, the road traces a line from Ribchester to Catterall to avoid the steepest hills, before angling off towards Lancaster – a route that no-one had thought of before seeing the evidence on the aerial flooding maps.

Roman roads were large structures, typically measuring 16 to 23ft (five to seven metres) wide and reaching a height of around one-and-a-half feet (half a metre) in the centre.

However, nearly two thousand years of weathering mean that they are often very difficult to spot at ground level.

Mr Ratledge said: 'The preservation of the remains varies massively.

Lidar can detect differences in the height of the land of as little as two inches (5cm), making it ideal for detecting hidden structures buried under the soil. However, some sections of Roman road are easily visible. This stock imaGe shows a section at Blackstone Edge, Rishworth Moor in Greater Manchester

'Parts of a road could still be half a metre high and easy to spot whilst in other parts it could be so subtle that you'd definitely miss it on the ground.'

WHAT'S LIDAR AND HOW IT'S USED? Lidar is a remote sensing technology that measures distance by illuminating a target with a laser and analysing the reflected light. It's used to make high-resolution maps used by a wide variety of professions. Farmers use Lidar to determine which areas of their fields to apply costly fertiliser, while archaeologists use it to reveal hidden structures. Self-driving cars use the technology for navigation. For example, Ford is using a combination of 3D maps and Lidar technology to allow its autonomous vehicles to 'see' road markings obscured by drifts of snow. It's used for environmental purposes such as monitoring deforestation and canopy heights as well as flooding - and devising flood defences. A worldwide network of observatories allow astronomers to use Lidar to measure the distance to reflectors placed on the moon, allowing the position of the moon to be measured with millimetre precision. Advertisement

Archaeologists Hugh Toller and Bryn Gethin have also revealed four previously 'lost' Roman roads using Lidar.

Mr Toller proved the course of a road from the Roman fort at Low Borrowbridge, near Penrith, to Kirkby Thore, the site of a Roman cavalry camp in Cumbria.

This is a missing part of a well-known road called the Maiden Way that continues towards Whitley Castle and Carvoran Roman Fort, Northumbria, near Hadrian's Wall

Mr Toller said: 'Often there are vague indicators of a route but not enough evidence to be sure.

'With Lidar we can spot any 'aggers' – a Roman embankment or rampart – and if you find 2 or 3km of these running dead straight there is nothing it can be except a Roman road.'

He is currently working on the precise location of four other Roman roads in northern England and there will likely be more discoveries, because the Environment Agency is making all its Lidar surveys available as open data, meaning anyone can use them.