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The topographical survey was required to be carried out within the water course which we undertook in line with SEPA’s General Binding Rules. 

Survey points were required within the Network Rail boundary which required staff to hold Personal Track Safety (PTS) cards and not be on or near the line as there was no rail track possession available.  The Rail positions were picked up using the reflectorless function within the total station.  On completion of each set up observations were made back to the reference object to ensure that no drift greater than ± 0.1m in 100.00m had occurred within instrument position.

Temporary bench marks were established around the site to allow the repositioning of the total station and ensure that all observations were captured within in a single coordinate system.  Each side of the structure and the meandering nature of the stream could be accurately captured when lines of sight did not permit.

The project was covered by our Standard Terms and Conditions.  Employers Liability was provided at £10m, Public Liability provided at £10m and Professional Indemnity level of £1m set for the topographical survey works.

The works were undertaken using a Trimble S8 High Precision 1” total station.  Angular Accuracy is accurate to 1” (0.0003°) with electronic distance measurement accurate to ± 1mm in prism mode and ± 3mm in direct reading (reflector-less) mode.  All observations were taken with prism where possible and DR readings reserved for sections of the bridge which were inaccessible or was unsafe to do so.

Contract at tender stage allowed for 2 days on site.  We undertook the topo survey in a day and used the second visit to pick up the location of the ground investigation to update our drawings.

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