The level value for A82 is now of historic interest only. Was established in January 2014 when seismic activity was believed to have A “recovery response” precise level network Using Global Navigation Satellite System technology. Seismic events interim “emergency response” benchmark networks were established A value of 50 feet ensured that levels specified on engineering works in Christchurch City would be expressed as positive values, even when working in New Brighton and Sumner where infrastructure is often situated below sea level.Įarthquakes experienced in the Canterbury region between 4 September 2010 andĢ3 December 2011 put the integrity of the Council’s network of benchmarks in An arbitrary figure of 50 feet (15.240m) above datum was chosen for the networks fundamental benchmark (A82), which was situated in the floor of ChristChurch Cathedral’s foyer. The origin of CDD dates back to February 1876, the early days of the Christchurch Drainage Board where the need for a common level was evident very early in the quest to control Christchurch's drainage issues.
For example a benchmark would be used to physically establish design ground levels for subdivisions, invert levels for pipe works and specified floor levels for new buildings in terms of CDD. In the case of Christchurch City Council, the datum used is known as Christchurch Drainage Datum (CDD).Ĭhristchurch City Council Benchmarks enable the ready establishment of normal-orthometric heights in terms of CDD within the greater Christchurch area. Christchurch City Council Benchmark Networkīenchmarks are levelled survey points assigned heights expressed in terms of a common datum (reference surface).
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