Mapping technologies

The 3D Coastal Mapping (3DCM) programme is using a combination of Light Detection and Ranging (LiDAR) and multi-beam echo sounder (MBES) technologies to map up to 40% of the New Zealand coastline.

LiDAR

LiDAR uses laser sensors mounted on aircraft that fly over a landscape to capture a 3D view of the land and seabed. 

The sensor measures the time it takes for light to travel back and forth from the sensor to the ground. Because the sensor can rapidly pulse a laser beam, it can capture a 'point cloud' (set of data points) of highly accurate 3D measurements.

Bathymetric LiDAR needs clear water for the laser to reach the seabed. In areas of turbidity (cloudiness in the water), the suspended particles of sediment prevent the laser light reaching the seabed. 

A 3D illustration showing an airplane scanning the ocean surface to reveal the seabed below. Positioned in the top right corner, a satellite assists with precise positioning. On the ocean surface, a small survey boat utilises echo sounders to capture detailed bathymetric data

Stylised rendering of Tuhua (Mayor Island) in the Bay of Plenty.     

MBES

The programme allows for some re-flights at different times to fill in any gaps caused by turbidity but where gaps still remain, we will use an alternative technology called multi-beam echo sounder or MBES. 

Similar to LiDAR, the MBES sensor, fitted to a boat, measures the time it takes for the acoustic pulse to travel back and forth from the sensor to the seabed. As the term suggests, multiple beams measure the depth across a swathe up to 4 to 6 times the water depth. 

Image showing a multi-beam echo sounder mapping the seafloor.

Seafloor mapping with multi-beam echo sounder

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