Hydrographic Surveying and Tides-1 in civil engineering.pptx

Surveying

1. HYDROGRAPHIC SURVEY Presented by: Fakhr Un Nisa Fatimah Nisar Mehreen Aslam Fahad Bhat Shadab yousuf

2. What are Hydrographic surveys? Hydrographic surveying as the name suggests are related to water bodies i.e Rivers ,Lakes etc. These type of surveying determine shoreline and underwater features. It is also sometimes called BATHYMETRIC SURVEYING as it determines physical features underwater like bottom of the bed that affect all the marine activities like marine construction etc . Besides this it also encompasses a wide variety of other objectives like measuring of tides , currents, gravity , earth magnetism etc

3. Why do we do hydrographic surveys? To determine the depth of bed. Measure shore lines Locate rocks and other objects for safe navigation To prepare navigation charts exhibiting the depths available for navigation Control floods, and to plan water supply and storage from rivers To develop water resources for power and irrigation.

4. Objectives of hydrographic surveying Measurement of Tides Waves (wavelengths, heights and frequency of waves) Construction of Sea-Defense works (navy, construction of defense structures) Determination of Bed-depths (harbor construction or sea defense either on sea or river) Location of underwater features (for excavation to construction of structures , cut/ fill) Topographic Maps (maps like that of land areas) Off-shore engineering and shipment (Trade, ports, harbors, stay and maintenance structures)

5. Procedure and Instruments used Typical procedure includes the following steps ; Setting up a vertical control Setting up a horizontal control Locating sounding points Sounding Instruments used are SIDE SCAN SONAR LIDAR ( Light detection and ranging ) GEO RADAR (Ground penetrating radar)

6. TIDES Alternate rise and fall of surface of sea water, caused by the gravitational pull of moon and sun on water bodies. These periodic oscillations occur due to variation of attractive forces of the moon and sun. These attractive forces vary because of change in relative positions of sun and moon wrt earth. The tidal phenomena are widely different at different places because of variation in depth of water and earth’s irregular land masses.

7. Theory of tides Newton’s equilibrium theory is the simplest and most theory to explain occurrence of tides. It is based on Coloumb’s law of attraction between heavenly bodies. The force of attraction between two celestial bodies acts in a straight line joining joining their centers and is directly proportional to the product of their masses and inversely proportional to square of distances between them. Tides caused due to gravitational pull of moon are called lunar tides. Tides caused due to gravitational pull of sun are called solar tides. The lunar tides are more important of the two, as moon is more closer to earth.

8. Theory of tides There is also centrifugal force due to rotation of earth about its axis. Tides are caused by resultant for of the two forces due to the celestial bodies and the centrifugal bodies.

9. Effect of moon The moon and the earth revolve around each other in ellipses in a period of about one month. The curvature of the elliptical path is such that the centrifugal forces of the moon and the earth balance the gravitational pull between them. But this happens only at center of mass. At the points which are nearer to moon than the earth’s center , the gravitational pull is greater than centrifugal forces, and the water surface is pulled out, causing the bulge of ocean surface. At the points which are away from moon, experience greater centrifugal force than the gravitational pull. The water surface is depressed. Thus there is one bulge towards the moon and one away from moon.

10. SOUNDING IN HYDROGRAPHIC SURVEYING Sounding is the measurement of depth below the water surface . It may also be defined as the measurement of depth of bed below the water surface . Sounding provides navigation charts . Range line: line along which soundings are made .These are usually fixed perpendicular to shore line and parallel to each other. Shore signal :each range line is marked with two signals .The signals are usually wooden tripods with white and coloured flag on top.

11. Equipments used for sounding Sounding boat Sounding rods Lead lines Sounding machine Fathometer Sounding rods :25-75mm dia ,3-5m long timber rods used for shallow waters

12. Echo sounding machine Also known as fathometer . Used when depth of water is too much . It works on echo property of sound . Determines the depth of water by measuring the time taken for sound waves to travel from location near the water surface to the bottom and back .

13. LIMITATIONS OF HYDROGRAPHIC SURVEYING Hydrographic surveying has several  limitations                                                                                                                                      1.Firstly, the process is time-consuming and requires significant resources. The survey itself can take months and even years, and the equipment is often expensive.                                                                                               2.Secondly, there are limitations on the accuracy and precision of the data collected. There are several reasons for this, including the nature of the water surface, the accuracy of the instruments, and the different tidal heights.                                                                                                                         3.Lastly, hydrographic surveying is weather dependent. Adverse weather conditions can hinder the survey and impact the accuracy of the data obtained.

14. CONCLUSION                                                                                                                                                                                             1.Hydrographic surveying plays a vital role in ensuring the safety of navigation in marine environments.                                                                                          2.Despite the benefits of hydrographic surveying, there are several limitations and challenges.                                                                                                                             3.Hydrographic surveying is an essential tool for mapping the oceans, waterways, and other navigational environments.                                                                                                                          4.To overcome challenges and limitations, the techniques must evolve, and the technology must improve.                                                                                                                                   5.The use of advanced techniques and technology would help combat these challenges and ensure that                                                                                                                                             6.Hydrographic surveying continues to be an essential tool for navigation. 

15. MULTIBEAM SONAR : This technology allows for a much larger area to be covered in one pass, providing high-resolution images of the seabed. UNMANNED AERIAL VEHICLES (UAVS): UAVs can capture high-resolution images of the water surface and coastline, enabling accurate mapping and monitoring. SATELLITE IMAGERY: High-definition satellite images can be used to identify changes in the coastline, water depth, and other features. AUTONOMOUS UNDERWATER VEHICLES (AUVS): AUVs can work independently, collecting data over long periods and in hard-to-reach areas without the need for a human operator. Advance technologies used in hydrographic surveying