Scientists have released new data that will help identify the risks posed by floods and sea level rise.
It's been a five-year project by Land Information NZ to measure the height of the land and its features, called vertical datum.
"LINZ has flown the length and breadth of New Zealand gathering airborne gravity data to update the vertical datum," said Land Information Minister Louise Upston.
"As a result of its work, planners, surveyors and engineers now have a consistent reference for measuring highs that is accurate to three centimetres."
Ms Upston says planners can use it to model the height of the landscape and buildings so they can see how water will move during storm surges and floods - New Zealand's most common natural hazard.
It also allows engineers to make sure sewage and water infrastructure runs downhill.