Hydrographic-Survey

Accurate positioning of the Survey Vessel and Marine Sensors is obtained by Differential Global Positioning System (D.G.P.S.)
This is a Satellite based navigation system and Differential corrections can be supplied by a shore-based reference station for high accuracy in-shore surveys (UHF Telemetry link provides sub-meter accuracies referenced to a Bench Mark).
Alternately, a satellite Global DGPS Correction service can achieve +/- 20cm. accuracies world wide without the need for shore-based stations.

Bathymetry
Bathymetric surveys obtain water depths of the area by single and dual frequency, Digital Echo Sounders.
Tidal corrections to reduce the water depths to a common datum can be obtained by Government predictions or by recording, digital Tide Gauges.

Side Scanning Sonar
Side Scan Sonar collects sonar data of the seafloor features and can be used for surface mapping, seafloor material classification (mud, sand, gravel, corrals, etc.) location of pipelines, cables, anchors, chains, shipwrecks and other natural or man made features.

Sub Bottom Profiling
Using Geophysical profiling techniques, the near surface sedimentary layers can be mapped. Different materials (mud, silt, sand, gravel, consolidated layers, bedrock) can be displayed and recorded as a continuous profile, and by analyses and interpretation of the data sections and isopachs can be produced.

Sea Bed Sampling
Samples of the sea floor material can be obtained for material classification and geotechnical analyses.

  • Grab Samplers take a small volume of the sea bed surface material and is commonly used for material classification
  • Gravity Drop Corers take up to a 2 meter sample of the seafloor sediments and is often used for mooring/anchor holding studies and cable or pipeline burial investigations
  • Vibro Corers can take up to a 6 meter core sample and is widely used for dredging/reclamation studies as well as mineral sands and mining evaluations.