Postcodes, or zipcodes if you prefer, are a powerful tool for geographic visualisation and analysis in New Zealand. While primarily designed to help deliver the mail, their standardised nature makes them useful for locating assets. Given a reference data set of postcodes with coordinates, it is possible to take a database of addresses (say, customers) and use the postcode as a common link or join. This allows the address database to be enriched by coordinates – a process known as geocoding. While these coordinates are only approximate (the centroid or centre point of each postcode), they allow the addresses to now be placed on a map where geographic patterns, such as clusters, may be revealed.
Postcode regions are polygon shapes which capture all addresses with a same postcode. They are often irregular shapes and sometimes feature holes and enclaves. Despite this, it is possible to use GIS or mapping software to assign colour to these regions to form a thematic map, also known as a choropleth map. While some care is usually required to ensure that the visualisation is statistically valid, thematic maps are visually powerful and a great way to communicate a variable across a geographic area.
We provide 4-digit Postcodes map data for New Zealand, as both centroids and regions data. Compatible postcodes / zipcodes data is also available for other countries, with seamless transitions across borders.