Severn Gauge Bar (SGB)
  
What is it ?

The SGB is our latest piece of equipment for high accuracy, high speed rail alignment observations; removing potential sources of error and providing additional value added information. Observations can be recorded automatically at a given spacing (as close as 100mm centres) and high accuracy gauge and cant reports can be generated.

The internal accuracy of the SGB is sub millimetre, producing data along rail running edges or centreline; a preference of some permanent way engineers. The system delivers quality data over longer run out distances, allowing more track survey output from a T3 possession and produces high accuracy track geometry survey data in an absolute coordinate system.

Why have it ?

In January 2008 the Times reported Network Rail’s Chief Executive, Ian Coucher’s call for greater engineering efficiency to meet the demands of the 365 day railway. Severn Partnership’s response combines state-of-the art surveying technology, bespoke survey methods and phased quality control to deliver night time engineering possession surveys on time and to a consistent high quality.

While permanent way design engineers increasingly demand greater accuracy and repeatability of survey data in absolute coordinate systems, they still want better quality data within the limited time available during Rules of the Route possessions. Survey repeatability is crucial, particularly with critical as-built surveys used to achieve safety standards and through alignment design (TAD) such as the A09 line speed enhancement project.