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Mapping the Ocean Floor

Map of Giggenbach volcano (using multibeam sonar)

Map of Giggenbach volcano (using multibeam sonar)

Two main methods are used to map the shape and depth of the seafloor.

Satellite altimetry

  • uses satellites to measures subtle but permanent differences in sea-surface height
  • global coverage
  • low resolution: 2-5 km
  • vertical accuracy: 200-300 m

Multi-beam sonar

  • uses multiple echo-soundings to map narrow (2-10 km) sections of the ocean floor
  • collected using scientific ocean going vessels or AUV’s – which is more expensive
  • limited coverage
  • good resolution:25-100 m (0.5m for AUV’s)
  • vertical accuracy: 1-2 m
Multi-beam sonar © NIWA

Multi-beam sonar © NIWA.