| The tidal flat | |
In tidal zones, surveys are necessary not only to validate and complete data from satellite and aerial image processing, but also to take qualitative and quantitative samples of benthic habitats.
Samples may be non-destructive (evaluation of habitat surface areas, rate of algal cover (main alga species), counting of invertebrate microspecies) or destructive (determination of species, density and biomass measurements, etc).
Field trips are usually undertaken on foot, but in some areas with difficult access (silted tidal flat), adapted machines are used to take samples (hovercraft, small tracked vehicle, etc). Geographical locations are pinpointed using GPS (Global Positioning System) or differential GPS (DGPS).

