CASE STUDY – Telephone Exchange

Located in the centre of Swindon’s former railway works, the Telephone Exchange is a three storey building that is in need of complete re-development and topographic surveys. Highworth Homes are a local property developer that are always on the lookout for interesting buildings to work with and will be taking this building through the planning process. The Telephone Exchange has stood empty for many years and will be converted into a series of apartments.



The Telephone Exchange is situated next to the main London to Bristol railway line which presented a number of challenges. Access to Network Rail land had to be arranged so that two elevations of the building could be surveyed. 
Proximity to the railway and the associated live overhead cables is a key consideration during the survey and also when designing and programming the refurbishment of the building. It must be proved that any scaffolding or other plant used during the work will not interfere with the railway in any way. Accurate clearance distances are crucial in gaining permission from Network Rail to work on or adjacent to their assets. 
The building is not currently connected to an electricity supply so is in darkness. Any survey method used in the basement needed to be able to work in the dark or lighting would need to be hired in adding to the project costs.

Digital mapping


The Carto Group assisted Highworth Homes with the access permissions and risk assessments for Network Rail to gain approval to undertake the survey. 

The survey of the structure itself was completed using a 3D laser scanner to ensure that no detail was missed. The point cloud created from the laser scan data means that the client has a ready source of data should they need any further information on the building. There would be no need to go back to site to obtain any further measurements for example. 

Deploying a laser scanner to site meant that the position of the railway, overhead cables and other assets could be determined without the need to work trackside. By surveying these features remotely, there was no need to arrange access to the track itself. Working on a live railway is dangerous, can be time consuming to organise and costly to implement which would have delayed the project and impacted on the return on investment for Highworth Homes. 

As a laser scanner can capture data in total darkness, there was no need to hire lighting to complete the survey of the basement.

Digital mapping


Elevations, floor plans, roof plan, cross sections and topographic survey were all derived from the laser scan point cloud. The site team also lifted manhole covers in the survey area to provide drainage information.

Digital mapping

 Added Value

Laser scanning was a better solution for this project than traditional survey techniques as it provides a very rich dataset.

Digital mapping
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