Surveying

Sound Velocity/Conductivity Temperature Depth Profiles

Density variations in the water column due to changes in the salinity, temperature and/or pressure result in a deviation in the path of the sound wave from the sonar equipment used to survey. As a consequence, soundings of depth will have an error. To ameliorate the problem, an instrument called a Sound Velocity Profiler is lowered through the water column measuring conductivity, temperature and pressure at regular intervals. This data is used to generate a profile which is entered into the MBES equipment that subsequently corrects the data for the effects of changes in water properties with depth.

Images of the CTD being lowered from the RV Celtic Explorer off the coast of Kerry (top) and the instrument is held just below the sea surface to allow it to acclimatise before lowering through the water column (bottom).

Vessels | Acquisition | Tides | Referencing | Sound Velocity | Ground Truthing | Survey Progress