CEN Meshblock Code

A meshblock is the smallest geographic unit for which statistical data is collected and processed by Statistics New Zealand. A meshblock is defined by a geographic area, which can vary in size from part of a city block to a large area of rural land. Each meshblock borders on another to form a network covering all of New Zealand, including coasts and inlets and extending out to the 200-mile economic zone. Meshblocks are added together to build up larger geographic areas such as area units and urban areas. They are also used to define electoral districts, territorial authorities, and regional councils.

Meshblock boundaries generally follow road centre-lines, cadastral property boundaries or topographical features (eg rivers). Expanses of water in the form of lakes and inlets are defined separately from land. The annual meshblock boundaries are used for the full calendar year from 1 January. While meshblock boundaries are continually under review, 'freezes' on changes to the boundaries are applied periodically. Such 'freezes' are imposed at the time of population censuses and during periods of intense electoral activity (e.g. general and local body elections).

Prior to 2015, meshblocks were allocated a unique seven-digit number. The first five digits were unique, and referred to the original 1976 meshblock code. The two end numbers refer to sequential meshblock splits to the original meshblock. When a meshblock is split the final two digits of the original meshblock number are changed. Exceptions to this rule are a small number of meshblocks where no more numbers in the sequence are available. Accordingly there were some meshblocks in Auckland and Tauranga City starting with 32xxxxx. Statistics New Zealand maintains a concordance file to ensure that boundaries relating to earlier meshblock patterns can also be produced.

From 2015 onwards, new technology has been introduced for splitting and nudging meshblocks, the process for allocating a unique seven-digit number has changed. New meshblock numbering is approximately sequential. The first meshblock number in this new sequential numbering pattern is 4000000. This differentiates meshblocks split from MB2015 onwards, and allows for a large number of unique seven digit identifiers to be allocated. Now when a meshblock is split it takes on the next available number, rather than following the former process described above. For example, a meshblock numbered 3254000 is split into two meshblocks. Using the new numbering process the system will assign the first available sequential numbers; 4000000 and 4000001.

There are two ways of amending meshblock boundaries.

1. Splitting is subdividing a meshblock into two or more meshblocks.
2. Nudging is shifting a boundary to a more appropriate position.

Reasons for splits and nudges include:

• to accommodate changes to local government boundaries, which are required by the Local Government Act 2002 to follow meshblocks for electoral purposes
• to accommodate changes to parliamentary electoral boundaries, following each Electoral Representation Commission review after each five-yearly Census of Population and Dwellings
• to make changes to statistical boundaries such as area units and urban areas
• to enable changes to census collection districts
• to improve the size balance of meshblocks in areas where there has been population growth
• to separate land and water ? eg mainland, islands, inlets, and oceanic are defined separately.
• to accommodate requests from other users of the meshblock pattern eg the NZ Police for their station, area, and district boundaries.