Hydrography is the science of surveying and charting bodies of water, such as seas, lakes, and rivers with an emphasis on the identification and description of shallow features or hazards which can affect safe navigation. The primary aim of INFOMAR as a marine mapping project is to conduct hydrographic and bathymetric surveys to describe the physical features of the seabed. This includes the measurement of water depth (bathymetry), definition of seabed structures and identifying sediment type and distribution, both on and below the seabed. INFOMAR routinely delivers three key Hydrographic datasets Bathymetry (or Water depth), Acoustic Backscatter and Water Column Data using a range of hydrographic and geophysical instruments.
Acoustic devices emit sound energy, in a series of continuous pulses, into the water column and detect the returning echoes. This is called sonar. Different echo strengths indicate different seabed features (or morphology) and the different physical characteristics of the seafloor. By knowing the speed at which sound travels through water (approx. 1500 m per second), depth can be calculated from the echo return time. This method produces extremely accurate measurements, which when coupled with accurate positioning systems and motion sensors can be used to produce very accurate seafloor maps. Similarly, by knowing the speed of sound through different rock and sediment layers under the seabed, our acoustic systems can measure the thickness of these layers to map the sub-surface structure of the seabed.
The primary acoustic device used by the INFOMAR programme is the Multibeam Echosounder (MBES).
In addition, there are Further Remote Sensing Techniques and instruments that can be employed depending on the type of survey we are conducting. They include the Singlebeam Echosounder (SBES), the Shallow Seismic Pinger / Sub Bottom Profiler (SBP), the Seismic Sparker and the Side Scan Sonar (SSS). Additional information on each and its application within INFOMAR can be found by following the previous link.