Wakehurst Place: measured survey

Related info
Read a blog post about our survey work at Wakehurst Place.
The Wakehurst Place Estate consists of c.200ha of land situated one mile to the north-west of the village of Ardingly in the High Weald of West Sussex. The property was bequeathed to the National Trust in 1964, and since 1984 has been administered by the Board of Trustees of the Royal Botanic Gardens, Kew. The Wakehurst Place Mansion is a Grade I listed building and the Stable Block is listed Grade II*, while an area of c.40ha of their associated parkland and gardens are Registered, Grade II*.
 
Wessex Archaeology were commissioned by the National Trust to undertake a Historic Buildings and Structures Survey, part of which was measured survey of the mansion, stable block and walled garden. The measured survey outputs would then be used as the basis for subsequent analytical and descriptive records of the structures.
 

Interior survey

Floor plans, a long section and two cross sections of the mansion were surveyed using Total Station Theodolite (TST) and a laser measuring device linked to a tablet PC running AutoCAD. This enabled the surveyor to build a 3D model in CAD directly on site, a highly efficient means of producing the required drawings.
 
Survey control was implemented using a closed loop traverse around the building, a commonly used surveying technique to ensure unavoidable error introduced by the tolerances of the survey instruments around the survey control network is minimised and quantified.
 

Exterior survey

The external elevations of the mansion in particular are complex, with numerous projecting gables and projections. This would have made an approach such as rectified photography very complicated indeed. Instead, terrestrial laser scanning (TLS) was used to record all the external faces of the buildings and structures, including accessible parts of the roofscape.
 

Drawing up

Both the internal and external elements of the measured survey were placed in a common coordinate system (British National Grid) using Global Navigation Satellite Systems (GNSS); this allowed them to be integrated to produce elevation drawings suitable for the subsequent interpretive stages of the project.

208

Conclusions

A combination of digital techniques can be deployed to undertake measured survey works to national standards most efficiently; choosing the right tools for the job in hand can reduce overall project costs whilst maintaining the highest standards of product. In this case, the use of TLS to record the external elevations was the most appropriate technique and not only resulted in drawn elevations as per the specification but provided a detailed point cloud suitable for other purposes including visualisation.
 

Acknowledgements