Standard Port Datum Descriptions
At a particular port the level of the water is expressed as a height above a local datum which is also the datum used for the depths of the sea on nautical charts (chart datum). This datum is defined with reference to permanent benchmarks ashore and the zero of the tide gauge. The datum adopted usually approximates Lowest Astronomical Tide (LAT) which is the lowest level the tide can be predicted to occur under normal meteorological conditions.
Zero points used in tide predictions
Auckland 5.233 m below B.M. 98-21 SO 69501 (LINZ code DD1N), a bronze plaque set in concrete into the road at the entrance to Captain Cook Wharf.
Bluff 8.620 m below Bluff Fundamental B.M. (LINZ code ABCC), a stainless steel pin set in concrete under iron cover, SE corner of Lee and Barrow Streets.
Dunedin 3.728 m below BM WW 83 (LINZ code AFEQ), a stainless steel pin set into the concrete base NW corner of G Shed, Birch Street Wharf.
Gisborne 4.091 m below B.M. GB 01 (LINZ code ACVP), a stainless steel pin set in concrete at the E end of No. 6 Wharf.
Lyttelton 4.401 m below B.M.UD 40 (LINZ code B40V), a stainless steel pin set in concrete block on main pier of overbridge to main wharves.
Marsden Point 4.816 m below the RNZN benchmark (LINZ code DJM9), an iron bolt set in concrete near the base of the light standard on the inshore east end of the Northport Ltd pier near the launch steps.
Napier 4.837 m below B.M. H 40 (LINZ code B3XM), a stainless steel pin set in concrete block under iron cover near the SW corner of Port of Napier Ltd office at railway crossing.
Nelson 5.772 m below B.M. N1 (LINZ code AC4T), a stainless steel pin set in the front steps to the old brick building in Wakefield Quay, known as Anchor House.
Onehunga 5.593 m below B.M. CC 65 (LINZ code ADLT), a stainless steel pin set in a concrete block near the easternmost corner of Shed B, Onehunga Wharf.
Picton 2.771 m below Elaine Cairn (LINZ code BQFK), a cairn of cement 0.61 m in height, 250m SE of the Ferry Terminal Building.
Port Chalmers 3.816m below Pin 1 SO 17533 (LINZ code DR0F), a stainless steel pin set in concrete under an asphalt and white tile cover immediately to the left of the steps to the Port Chalmers Museum (ex Post Office building).
Port Taranaki 6.721 m below New Plymouth Fundamental B.M. (LINZ code AGMH), a stainless steel pin set in concrete block, 0.305 m under concrete cover and iron cap on east side of Rigger Shed, Port Taranaki.
Tauranga 4.103 m below B.M. BC 84 (LINZ code B309), a stainless steel pin set in the concrete foundation at the NE corner of the Port of Tauranga Ltd administration building.
Timaru 5.300 m below B.M. UD 44 (LINZ code B2YB), a stainless steel pin set in the concrete base of the light tower at the SW end of the No. 1 Wharf goods shed.
Wellington 3.002 m below B.M. K80/1 (LINZ code ABPB), a stainless steel pin set in concrete under iron cover, in Featherston Street at the intersection with Lambton Quay.
Westport 7.327 m below B.M. Harbour Master's Office (LINZ code DJMC), a stainless pin set in concrete, immediately above steps to pilot boat, adjacent to Harbourmaster's Office on the main wharf.