From satellites to divers: choosing a mapping method

Satellite imagery, acoustic surveys and underwater video each see a different part of the seabed. How to combine them.

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© dronepicr · CC BY 2.0 · Wikimedia Commons

Three scales, three tools

No single method maps a meadow from its shallow edge to its deep limit. Multispectral satellite imagery works in clear, shallow water; acoustic methods such as side-scan sonar reach deeper; towed cameras and divers provide the ground truth both need.

What each method sees

  • Aerial view of the coastline of Rhodes New Town, Greece (51698843033)
  • Campagne FUTUNA - Visualisation de la bathymétrie fournit par le sondeur multifaisceaux (Ifremer 00554-66590 - 16880)
  • Monitoring des fonds coralligènes par une technique de photoquadrat (Ifremer 00424-53560)
Aerial view of a coast, multibeam bathymetry on screen, a diver with a photo-quadrat: three ways of seeing the seabed. © dronepicr · CC BY 2.0 · Wikimedia Commons — © Stephane Lesbats (IFREMER, Pôle Images, Centre Bretagne - ZI de la Pointe du Diable - CS 10070 - 29280 Plouzané, France) · CC BY 4.0 · Wikimedia Commons — © Olivier Dugornay · CC BY 4.0 · Wikimedia Commons

Validating the map

Report the accuracy of each class against independent ground-truth points. A map without a validation table should be treated as a hypothesis.

Bathymetry of the north-western Mediterranean (EMODnet).
Bathymetry of the north-western Mediterranean (EMODnet).Layer: EMODnet – Bathymetry (shaded relief) · © EMODnet Bathymetry Consortium, CC BY 4.0Open in the EMODnet Map ViewerOpen this area in the geoportal

Sources

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Catalogue

Chapter
Mapping and data
Level
Intermediate · 9 min read
Habitat group
Methodology
Keywords

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