Groundbreaking satellite imagery reveals scale of landslides after severe rainfall on West Coast

The state of emergency in Buller has been extended as the council assesses flood damage and Coasters brace for more heavy rain tonight.

Relentless rain over the past couple of weeks has caused massive slips and rockfalls.

Groundbreaking technology has been used to capture satellite images revealing the scale of the impact.

The devastation on the ground is obvious but the view from the sky reveals more.

Satellite imagery captured in the 24 hours after severe rainfall on the South Island's West Coast earlier this month shows some major landslides - one which wiped out everything in its path.

"One of them is about four rugby fields in size and about 10 stories high and ran about a kilometre or so down and across and covered the entire valley floor," says GNS Science principal scientist Dr Simon Cox.

It's the first real-life test of the Matariki project, which aims to transform environmental monitoring by using automated satellite mapping of landscape change.

"To get metre-scale change, and get a metre-scale on one model and perfectly a metre precision on the next one has never been done before as far as I'm aware," Dr Cox says.

"We want a very fast response time on these updated maps so we can have a rapid response on these events," adds Otago University school of surveying Associate Professor Pascal Sirguey.

It's information that could potentially save lives - especially in popular tourist spots like Aoraki Mt Cook.

"The Southern Alps have been destabilised by the melting of the glaciers and the decreasing size of the snowfields leaving them ready for when an event like this comes and triggers collapse," Dr Cox warns.

The improved method of measuring can help us understand how climate change can inform the scope of these hazards.

"We can take the lessons from there and apply them to other landslides throughout New Zealand," Dr Cox says.

Updating not only our topographical maps, but also our knowledge.