In the word “Hydrographic” the first part “Hydro” refers to water & the second part “Graphic” refers to a plot map or chart or draw a diagram. So in the hydrographic survey, we conduct the survey inside the water bodies just like rivers, sea, Lakes, or any other deep-water bodies, which is also known as the bathymetric survey.
So the Definition of Hydrographic survey: Hydrographic survey is the survey of the underwater surface of Sea or any river or lake or any deep water body for all types of underwater activity including marine activity such as dredging or underwater construction work.
Technology Used: In the Hydrographic survey “Reflection of Sound” technique is used with the help of a sounding beam.
Reflection of sound states that when we send any sound in any medium it will be returned to the same place after hitting an obstruction.
In a Hydrographic survey we use the sounding beam fitted at the bottom of a survey boat to send sound to the bottom of the water to hit the surface below Sea or River or lake, After hitting the surface the sound returns to the beam. We calculate the distance by calculating the time taken by the sound to travel from the bottom of the boat to hit the surface & return to the ship after applying sound velocity correction.
Nowadays we use multiple sounding beams for more accuracy in surveying and the equipment with multiple sounding beams attached to the survey boat is known as “Multi-beam Echo sounder”.
You can refer to the video above to know how the survey is being conducted inside Sea.
In the survey boat in the video, we are using sea beam 1000 along to get the depth of the sea & a GPS also attached to it to get the coordinate. This survey boat is fully automated for hydrographic survey with the help of Sea beam 1000 & the GPS. We just have to monitor the route of the ship and the map on the monitor to conduct the survey.
After completion, we will take all datasheets for working on volume calculation or to fulfill any other requirement.
Application / Requirement Of Hydrographic Survey:
We are dependent on hydrographic surveys for so many activities like Cargo or Passenger movement inside water by any boat or ship, Underwater structure construction, Tidal wave measurement, and many more activities. After conducting the survey we conduct dredging or drilling to fulfill our requirements.
Dredging activity conducted to maintain sea or canal bottom level for ship movement or new berth construction.
Conclusion: Hydrographic survey is the heart of all marine activity. It is completely different from the land survey because in the case of the land survey we can see the surface but inside water, without a hydrographic survey, we can know nothing, what is inside the water.