Stone Age builders began construction on the site about 5,000 years ago by digging a circular ditch and a high bank. Approximately 80 bluestones each weighing about four tons, were brought by raft from the Preseli Mountains in Wales about 4,100 years ago. A hundred years later, the bluestones were removed and Sarsen stones weighing up to 50 tons were brought from nearby Marborough Downs. It has always baffled scientists how the huge stones were moved, but they speculate they were brough on sledges pulled over log rollers. "After bringing them to the hillside, explains Dave Batchelor, archeologist with English Heritage, "stoneworkers began carving and shaping each stone, using implements made from the same stone." There is a layer of stone shavings beneath Stonehenge today. Many mysteries remain, such as how the lintels were placed on top of the upright stones. The monument is truly a landmark to engineering.
MUSE Virtual Presence created a large-scale virtual model of Stonehenge with a mathematically correct model of the night sky and virtual sunrise. The model was debuted in 1996 at the London Planetarium by the company and famous astronomer Patrick Moore, and Sir Jocelyn Stevens, former Chairman of English Heritage. A series of demonstrations at conferences followed.
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Using accurate map data and cameras with measuring techniques, the model became a tool for the planning process for the monument. Data from a Leica imaging system, which uses stereo camera views to produce point cloud data, was the basis for the 3D model. The point cloud data was converted into a wireframe mesh of each of the stones, flat shaded to give them form, then applied the left-eye photographic image from the Leica cameras as a texture map. The decimation of the wireframe stones into a set of lower resolution models was done by hand. At that time, the software decimation tools that we rely on today did not exist. The nighttime star field data came from astronomical software. "We used Right Ascension and Declination for stars with a greater Apparent Visual Magnitude than 3.55," says Professor Stone. "Right Ascension is measured in hours (24) and had to be converted to degrees, and Declination was measured in degrees (-90 to +90). These can be thought of as the longitude and latitude lines that span the earth. The star positions were then projected onto a sphere surrounding the Stonehenge model from the celestial equator (i.e. the center of the earth). Once the stars were spherically projected, they were scaled according to their Apparent Visual Magnitude." The position of Stonehenge from the center of the earth then had to be taken into consideration as the "star sphere" was being projected from the celestial equator. This involved shifting the whole star sphere and then spinning the sphere around an axis close to the North Star.