Christchurch City Council benchmark level values are available via the Canterbury Maps site. These values supersede all previously published benchmark data.
Benchmarks are levelled survey points that have assigned heights expressed in terms of a common reference surface (datum). In the case of Christchurch City Council, the datum used is known as Christchurch Drainage Datum (CDD).
Christchurch City Council Benchmarks enable the ready establishment of CDD normal-orthometric heights within the greater Christchurch area. They are predominately used to establish site level control for civil construction works and to provide control for monitoring the city drainage network.
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.
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 foyer. 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 may be situated below sea level.
Christchurch Drainage Datum was initially called Christchurch Drainage Board Datum but upon an amalgamation of the Drainage Board and its activities into the Christchurch City Council, the name was changed to Christchurch Drainage Datum (CDD).
The Canterbury Earthquake Sequence that followed the 4 September 2010 Darfield earthquake inflicted significant structural damage to ChristChurch Cathedral, rendering A82 unusable.
Land Information New Zealand’s Hagley Fundamental (AF30) has been adopted as the new fundamental mark for Christchurch Drainage Datum. The level value for AF30 is 5.6082m above Lyttelton Vertical Datum 1937, which equates to 14.6512m CDD.
Christchurch Drainage Datum is offset from Lyttelton Vertical Datum 1937 by 9.043m.
The earthquakes experienced in the Canterbury region circa 2010 put the integrity of the Council’s historic benchmark network in doubt.
In response to each seismic event, a new Global Navigation Satellite System derived benchmark network was established. The current network is the July 2019 Network.
Queries regarding the benchmark network can be sent to firstname.lastname@example.org
To receive notification on changes to the benchmark network please subscribe to Council benchmark network notices.