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Laser scanning uncovers new Stonehenge evidence
English Heritage experts have used3D laser scanning technology to discover new evidence of the importance of the two solstices to its creators.
The laser scan has revealed significant differences in the way the stones were shaped and worked. These differences show that Stonehenge was not only aligned with the solstices, but that the view of the monument from the Avenue, its ancient processional way to the north east, was particularly important.
To approach and view the stone circle from this direction means that the midwinter sunset had special meaning to prehistoric people, and that they made deliberate efforts to create a dramatic spectacle for those approaching the monument from the north east.
A detailed analysis of the first comprehensive laser survey of Stonehenge reveals that those stones on the outer sarsen circle visible when approaching from the north east have been completely pick dressed - that is, the brown and grey crust on the surface has been removed exposing a fine, bright grey-white surface. By contrast, the outer faces of surviving uprights in the south-western segment of the circle were not pick dressed.
These stones facing north-east are also the largest and most uniform in shape, unlike the south-western segment of the monument where there are several smaller and more irregular stones. The lintels are also exceedingly well worked and finished, compared to those that survive elsewhere in the monument.
The study also shows that the techniques and amounts of labour used vary from stone to stone. These variations provide almost definitive proof that it was the intent of Stonehenge’s builders to align the monument with the two solstices along a NE/SW axis.
The sides of the stones that flanked the solstice axis were found to have been most carefully worked to form very straight and narrow rectangular slots. These stones include two of the north-east facing sarsens in the outer circle, the Great Trilithon in the inner sarsen horseshoe, and a now isolated upright stone in the south-west segment of the outer circle.
Since all other stones have visibly more natural, less neat outlines, this strongly suggests that special effort was made to dress those that flank the NE/SW axis to allow a more dramatic and obvious passage of sunlight through the stone circle on midsummer and midwinter solstices.
Professor Clive Ruggles, Emeritus Professor of Archaeo-astronomy at University of Leicester, said: “This extraordinary new evidence not only confirms the importance of the solstitial alignment at Stonehenge, but also shows unequivocally that the formal approach was always intended to be from the north-east, up the Avenue towards the direction of midwinter sunset.
"We see how the utmost care and attention was devoted to ensuring the pristine appearance of Stonehenge for those completing their final approach to the monument at the two times of the year when sunlight shines along the alignment - when those approaching had the midsummer rising sun behind or the midwinter setting sun ahead.”
Loraine Knowles, Stonehenge Director at English Heritage, said: “The new presentation of Stonehenge will enable visitors to appreciate the importance of the solstitial alignment far better. It’s why we are closing the A344 – which severs the alignment - to enable the stone circle to be reunited with the Avenue.”
The new Stonehenge visitor centre at Airman’s Corner, 1.5 miles west and out of sight of Stonehenge, is scheduled to open in late 2013.
Analysis of the laser scan has also led to the discovery of many more prehistoric carvings, including 71 new Bronze Age axeheads, which bring the number of this type of carvings known in Stonehenge to 115.
Susan Greaney, Senior Properties Historian at English Heritage, said: “We didn’t expect the results of a laser scan to be so revealing about the architecture of Stonehenge and its function.”
English Heritage commissioned the first comprehensive laser survey on Stonehenge in 2011. Archaeological analysis was then carried out to examine the high-resolution data that was produced for all the stone surfaces.