Mt Ruapehu is to become one of the only volcanos in the world to be watched around the clock by high-speed radar.
Massey University and the University of Hamburg in Germany have set up a doppler radar at Whakapapa ski field focused on the crater lake.
Massey University vulcanologist Shane Cronin says the radar can detect how big an eruption is and in which direction it is heading.
Professor Cronin says the radar can work in any weather as an early warning system, but will also be a valuable tool to gather data on eruptions for scientific research.
The only catch is there will have to be an actual eruption at the mountain before the radar is fully operational, so it can be calibrated.