MARINE GIS Training ( Geophysical Survey ) in Portharcourt

TRAINING ON MARINE GIS ( Geophysical Survey ) in Portharcourt
This course will cover
A Generate interactive map imagery of the following derived data layers:
Location map with limits of the survey area;
Bathymetric map showing the depths, slope and bathymetric hill shading results;
Backscatter data map showing boundaries between sub bottom Geology
Map showing the track plot of the vessel position, indicating the region of the patch test calibration.
To develop existing methods to process and analyze backscatter data in order to deliver geological classified maps of bottom sediments.

B Multibeam bathymetry, side-scan sonar, sub-bottom acoustic and seismic-reflection profiles can be merged into a digital 3D environment for interpreting seafloor morphology and/or sub-bottom geology (the seafloor and the stratigraphy of the material that underlies .
Mutibeam Echo sounder

the MBES transmits sound waves in a wide fan . The full width of the fan, commonly referred to as the swath width
A multibeam echo sounder consists of many transducers that send out multiple sound pulses
covering a wide swath beneath the survey vessel. A multibeam echo sounder makes
it possible to get 100% coverage of the survey area without having to interpolate between the
survey lines Acoustic backscatter is often collected with multi-beam echo-sounders (MBES). Acoustic backscatter from the seabed is collected for its use in seafloor imaging, seabed mapping, and habitat mapping The basic principle of echo sounding is simple: a sound source (also called a transmitter, projector or Tx) transmits a sound pulse (ping) into the water at a known time. The sound pulse is reflected (echoed) from the seafloor or other targets and the time of its return is recorded by a receiver (Rx). The two-way travel time (TWT) is then calculated. Given that the speed of sound through the water column (v) can be measured, the TWT may be converted to local depth (D) as: (1)
In any fluid, the propagation speed of pressure waves, such as sound, is governed by two physical quantities: the fluid's density and the bulk modulus (i.e. its compressibility). The sound speed (v) is calculated using the bulk modulus (K) and the density (?) as: (5)
The speed of sound thus increases with decreasing compressibility (larger bulk modulus), but decreases with increasing density.

The Marine Magnetometer……. is the best tool for locating sunken ships, lost anchors, buried pipelines, and other underwater objects containing ferrous metal
The magnetometer sensor is towed 200? behind the survey vessel to prevent the magnetometer data from being influenced by ferrous metal aboard the boat.
Sub-bottom profilers …… Sub-bottom profilers (SBPs), also known as sediment profilers, are echo sounders designed to penetrate the seafloor and measure the travel time (depth) to layers in the uppermost sediments. They operate on the same principle as SBESs, but with higher output energy levels and lower frequencies, which allow penetration into sedimentary material below the seaflo. SBPs usually operate with frequencies in the range 1–20 kHz and penetrate up to about 100 m in soft, low-absorbing sediments, but commonly only several tens of metres in many environments. Penetration >10 m in soft sediments may be achieved occasionally with frequencies >20 kHz in relatively shallow water (<100 m water depth).
Side scan survey …….The fundamental purpose of a Side scan survey is to provide acoustic images of the seafloor rather than measurements of depth . Side Scan receiver detects sound that is Backscattered from seafloor We have two types of digital side-scan sonars to produce acoustic images of the seafloor: our 100-500 kHz side-scan is used for geological character-ization and search & recovery surveys, while 600-1200kHz side-scan is used for high-resolution archaeological and marine vegetation surveys.The acoustic images are interpreted to produce maps that show the lateral extent of surficial lithology (silt, sand, gravel), and natural (bedrock), cultural (shipwrecks, pipelines), or biological (fish, vegetation) features on the seafloor.
Seismic profiling……..the seismic-reflection/refraction …..A good method for mapping sub-bottom geology .There are two main types of seismic-reflection mapping: 2D seismic and 3D seismic. The former acquires sub-bottom information along 2D profiles, whereas the latter acquires 3D data in a regular and closely-spaced grid. A fully imaged 3D cube, extending from the seafloor to the base of the acoustic penetration, is derived from a 3D seismic-reflection survey, whereas a 2D survey produces a set of interpretable individual sub-bottom profiles.
Sub-bottom profilers …… Sub-bottom profilers (SBPs), also known as sediment profilers, are echo sounders designed to penetrate the seafloor and measure the travel time (depth) to layers in the uppermost sediments. They operate on the same principle as SBESs, but with higher output energy levels and lower frequencies, which allow penetration into sedimentary material below the seaflo. SBPs usually operate with frequencies in the range 1–20 kHz and penetrate up to about 100 m in soft, low-absorbing sediments, but commonly only several tens of metres in many environments. Penetration >10 m in soft sediments may be achieved occasionally with frequencies >20 kHz in relatively shallow water (<100 m water depth).
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