GPR is a non-intrusive survey technique which can determine construction detail and thickness. It was therefore ideal for the survey to understand this unique and somewhat complex Grade II listed monument.
The Wellington Monument is a triangular tower, 24 m wide at the base and 53.34 metres high, located on the highest point of the Blackdown Hills1.9 miles south of Wellington in the English county of Somerset. It is a grade II listed building.
The monument is built of local stone a Calcareous Grit Sandstone. The base has an Egyptian winged panel above the studded iron door and is surmounted by a coved dentil cornice. A counterweight hangs inside the top of the monument to help balance it in windy weather. An internal staircase ascends to a viewing platform, which has three circular windows, one on each face.
The monument was designed to commemorate the Duke of Wellington's victory at the Battle of Waterloo. Construction of the original design commenced in 1817; a revised and cheaper design was eventually used, though, and building was completed in 1854. It is now owned by the National Trust, who closed the monument to the public in 2005, because of falling stone debris. Surveys have shown that extensive renovation work will be needed to reopen the internal staircase to the viewing platform.
In May 2015, Sandberg used Ground Penetrating Radar to investigate the construction detail and help identify weaknesses.
Mr Ken Evans, the trust's building surveyor, said the ground penetrating radar study was one of several being carried out to "understand this unique and somewhat complex monument. The ground-penetrating radar seeks to identify voids and gaps in the stonework under the surface but should also tell us more about the materials which were used to build the obelisk."
Results from the ground penetrating radar survey will also be used to build a computer model of the obelisk and help with a "more effective repair approach".