A New Zealand you have never seen - how 3-D laser tech reveals the 'bare' West Coast

GEORGE HEARD/STUFF
Drone footage shows full extent of the damage to the Waiho Bridge, near Franz Josef on the West Coast, in March 2019.

New maps that show the precise makeup of the West Coast, warts and all, have been released. They can be used for everything from farming to engineering. KEITH LYNCH reports.

They are called LiDAR (Light Detection and Ranging) maps, and they can be used to create a picture of the “bare” earth.

In 2018, a Government initiative made millions of dollars available to better map regional New Zealand.

The first batch of maps, showing the West Coast, has now been released. More are expected to follow soon. This is what is going on.

A surface model of Westport shows a detailed view of land surface features.
LINZ/Supplied
A surface model of Westport shows a detailed view of land surface features.

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What is LiDAR?

LiDAR (Light Detection and Ranging) is a technology that can be used to create high-resolution models of an environment.

In this particular case a plane, armed with LiDAR equipment, would have flown back and forth over the West Coast. The LiDAR equipment shoots out pulses of light and that light is reflected back. What matters is precisely how long it takes for the light to bounce back.

Why? It takes that miniscule fraction longer for the light to bounce back from a depression in the ground than from a slight hump on the land.

This data allows the creation of precise 3-D maps, like the one you see below.

A Digital Elevation Model (DEM) snapshot of the Buller River and its floodplain, south of Westport. LiDAR has the capability of capturing information not easily seen in aerial imagery alone. You can clearly see different land features, including the many pathways/rivers/streams/creeks that cross the land.
LINZ
A Digital Elevation Model (DEM) snapshot of the Buller River and its floodplain, south of Westport. LiDAR has the capability of capturing information not easily seen in aerial imagery alone. You can clearly see different land features, including the many pathways/rivers/streams/creeks that cross the land.

The LiDAR work on the West Coast would have initially captured buildings, other structures and trees and plants. They reflect light too.

But they can be removed to create what is called a Digital Elevation Model (DEM), which is often described as a representation of the “bare earth”.

LiDAR is not just used for overhead mapping. It is also used by autonomous cars to map what is around them and avoid crashes.

Apple has also announced it will be using LiDAR on its iPhone 12 Pro and iPad Pro to improve augmented reality apps.

Radar, which was primarily developed for military use, works similarly but it uses radio-waves.

What exactly are these maps used for?

They have a lot of applications – everything from engineering to understanding what the ground looks like before an archaeological dig.

A model of the Buller River shows the many paths rivers take across the land.
LINZ/Supplied
A model of the Buller River shows the many paths rivers take across the land.

Farmers could use it to build a clear picture of their land to ensure runoff does not end up in waterways. Councils can use it to understand what would happen if the coast was inundated by, for example, a change in sea levels.

It could be used to see what the land is like under forest cover, to plan for access roads. It can be used to determine just how far inland a tsunami could travel.

Minister of Land Information Damien O’Connor outlined the example of the Waiho Bridge which was swept away during flooding in 2019.

The Waiho Bridge in Franz Josef was taken out by floodwaters.
George Heard/Stuff
The Waiho Bridge in Franz Josef was taken out by floodwaters.

LiDAR would allow new developments, like bridges, to be built in more appropriate locations, he said.

How did this project come about?

At present there is LiDAR mapping for about 20 per cent of the country. You can check out exactly what is available here. The idea is that this initiative will make LiDAR maps available for 80 per cent of New Zealand.

It is part of a project by the Provincial Growth Fund, a scheme to boost economic development in the regions, spearheaded by former regional development minister, NZ First’s Shane Jones. (Labour is moving ahead with replacing that fund.)

In October 2018, Jones announced up to $19 million in co-funding to do the LiDAR 3-D mapping. Councils needed to apply for funding and were supported by LINZ to ensure the data was available and nationally consistent.

Ten regions asked for money. The West Coast was the first to complete its mapping