Hydrography & Bathymetry

1. 6/6/2023 1
Presentation
Physical & Chemical Oceanography
Course Code |PCO 501
Presented By
Abdul Alim Kamran
MS Roll 0123/04
Department of Marine Bioresource Science
Faculty of Fisheries
Chittagong Veterinary & Animal Science University

2. Presentation Outline
Chapter-6: Hydrography and Bathymetry
Chapter-7: Chemistry of Sea water
Chapter-8: Dissolved Gas
6/6/2023 2

3. Chapter 6
Hydrography and Bathymetry
6/6/2023 3

4. IHO Definition
Hydrography is the branch of
applied sciences which deals with
the measurement and description of
the physical features of oceans,
seas, coastal areas, lakes and rivers
as well as for the
• safety of navigation and
• in support of all other marine
activities,
• including economic development,
security and defense, scientific
research, and environmental
protection ”.
6/6/2023 4
Hydro Graph
Water
Body
Images
with
information
Hydrography

5. Hydrography is
really a multi-
disciplinary science
drawing on many
fields to gather and
process data
6/6/2023 5

6. Uses of
Hydrographic
Surveying
Shore lines
can be
determined
Navigation
Chart
Preparation
River and
stream
discharge
measurement
Locating
mean sea level
Scouring,
silting and
irregularities
of the bed can
be identified
Tide
measurement
6/6/2023 6

7. 1.Safety of navigation.
2.This allows ships to safely travel in
and out of ports, saving lives and
property and protecting the
environment.
1.Humanitarian relief
2. in the aftermath of a natural
disaster frequently arrives on a ship.
Until a clear and safe route to shore
is established by hydrographers,
supplies cannot reach those in need.
Environmental management
in coastal areas depends on
knowledge of changes in the marine
environment. Hydrographic surveys
determine changes to bathymetry
and seafloor characteristics.
Commercial fishing
1. uses nautical charts and other
hydrographic products to locate
fishing grounds and navigate safely.
Benefits of
Hydrography
6/6/2023 7

8. 1. Coastal Hydrography:
It is concerned with the development of ports and harbors, coastal erosion problems, the utilization of harbor and
coastal conservation services and, especially, the safety of navigation in coastal waters.
2. Off-shore Hydrography:
It is concerned with the provision of hydrographic data as an extension of the coastal zone normally
encompassing the continental shelf, the development of mineral deposits, including hydrocarbons, and the
provision of data for fisheries management.
3.Oceanic Hydrography:
It is concerned with the acquisition of hydrographic data in the deep ocean areas for the depiction of sea-floor
geomorphology.
Three Aspects of Hydrography
6/6/2023 8

9. PARAMETERS
The parameters encompass –
 bathymetry,
 geology,
 geophysics,
 tides,
 current
 waves
 certain other physical properties of sea water
6/6/2023 9

10. Principal Components of Hydrographic Survey
Four(4) Components
1. Positioning
2. Water Depth
3. Underwater Features
4. Seafloor Characteristics
6/6/2023 10
Hydrographic Survey Nautical Chart
End Result

11. Nautical Chart
6/6/2023 11
1.Depths
2.Lighthouses
and Beacons
3.Rocks, Shoals,
and
Obstructions
4.Wrecks
5.Channels
6.Anchorage
7.Navigational
Aids
8.Landmarks
9.Fishing Areas
A nautical chart is a graphic representation of a
maritime area and adjacent coastal regions.

12. Hydrographic Survey Equipment
1. Multibeam Sonars: Transmit sound energy
and analyze the return signal (echo) that has
bounced off the seafloor or other objects
2. Lidar
3. Laser
Scanners
4. Sound Speed
Profilers
5. GPS for
Surveys
6.
Measuring
Water Levels
6/6/2023 12

13. Sound speed profilers
Collecting bathymetry with sonars in the marine environment
means measuring the path and travel distance of sound from the
transmit point, to the seabed, and back again to the receive point
To measure the density of water, the coast survey utilizes
different types of sound velocity profilers
6/6/2023 13

14. Laser scanners
Measures and locate features such as rocks, islets, and small islands
The laser head produces sixteen laser beams, which reflect off the
target object and are received back by the laser head
The computer then uses that data along with precise positioning and
attitude (roll and pitch) data, to determine the height and location of
the object
6/6/2023 14

15. LIDAR
6/6/2023 15
LiDAR (Light Detection and
Ranging) is a remote sensing
technology that measures the
distance from a sensor to an
object.
A laser illuminates the target
through light pulses which then
return to the sensor, and the time
it takes for the laser to return is
calculated to determine the
distance to the object.

16. How Does Lidar
Work?
1
A typical lidar
sensor emits
pulsed light
waves into the
surrounding
environment.
6/6/2023 16
3
Times of flight
The sensor uses the
time it took for each
pulse to return to the
sensor to calculate
the distance it
traveled
2
These pulses
bounce off
surrounding
objects and
return to the
sensor.

17. 6/6/2023 17

18. 6/6/2023 18
RADAR (Radio Detection & Ranging)
The RADAR is the technology used for detecting objects by measuring distance, angle & radial
velocity with respect to the site such as aircrafts, ships, space-crafts, guided missiles, weather
formations, etc. by the use of radio waves.

19. SONAR
• Sound Navigation and
Ranging(Sonar),is
helpful for exploring
and mapping the
ocean because sound
waves travel farther in
the water than do
radar and light waves
• Types
1.Active Sonar
2.Passive Sonar
6/6/2023 19

20. SONAR (Sound Navigation & Ranging)
6/6/2023 20

21. Side Scan Sonar
Side-scan sonar is a category of active sonar system for detecting and imaging objects on the
seafloor. The multiple physical sensors of the sonar — called a transducer array — send and
receive the acoustic pulses that help map the seafloor or detect other objects. This array can
be mounted on the ship’s hull or placed on another platform like a tow-fish.
6/6/2023 21

22. Side Scan Sonar(Video)
6/6/2023 22

23. RADAR LIDAR SONAR
Uses Electromagnetic
waves
Uses laser beams Uses sound waves
Determines distance from
objects and their angular
positions
Measures the height,
distance and density
Used to detect
underwater objects
No 3D replica of the
object
3D images with high
resolution:
Mostly used to find
actual sea depth
It can operate in cloudy
weather conditions and
during the night
It is adversely affected by
smoke, rain, and fog:
Is not affected by
surface factors
RADAR takes more time
to lock on an object
Data can be collected
quickly
Passive sonar does not
require a transmitter
and a receive
6/6/2023 23
RADAR Vs LIDAR Vs SONAR

24. GPS
6/6/2023 24
The Global Positioning System (GPS) is
actually a constellation of 27 Earth-orbiting
satellites (24 in operation and three extras in
case one fails). The U.S. military developed and
implemented this satellite network as a military
navigation system, but soon opened it up to
everybody else.
GPS stands for Global Positioning System. It is a
satellite-based navigation system that provides
location and time information in all weather
conditions, anywhere on or near the Earth's
surface.

25. Components of
GPS
a)Satellites – They serve like stars in
the constellation.
b)Ground stations – They
monitor and control satellites. Ground
stations also identify their location.
c)Receivers –Receivers are
constantly listening for signals from
the satellites. Highly advanced
receivers can even identify the exact
location within a fraction of an inch.
6/6/2023 25

26. 6/6/2023 26
1. Space segment
2. Ground Control
segment
3. User equipment
segment

27. How does GPS works
• Satellites act like the stars in constellations—we know where
they are supposed to be at any given time.
• The ground stations use radar to make sure they are actually
where we think they are.
• A receiver, like you might find in your phone or in your parents
car, is constantly listening for a signal from these satellites. The
receiver figures out how far away they are from some of them.
• Once the receiver calculates its distance from four or more
satellites, it knows exactly where you are.
6/6/2023 27

28. How does GPS works
6/6/2023 28
Trilateration is defined as the
process of determining the
location based on the
intersections of the spheres.
The distance between the
satellite and the receiver is
calculated by considering a 3-
D sphere such that the
satellite is located at the
centre of the sphere

29. GPS Vehicle
Tracker System
6/6/2023 29

30. Fig: Hydrographic Processing Software
 A software designed to process hydrographic data
 This software allows for the creation of hydrography maps, target
detection, a difference analysis between new and old surveys as well as
many other features for a wide variety of applications
Hydrographic Processing Software
6/6/2023 30

31. Hydrographic Processing Software
 HIPS and SIPS: capable of integrating bathymetry, laser scanner, seafloor imagery, and water
column data processing in a single application
 ISE Post-Processing Software: Innomar ISE is a powerful but user-friendly and easy to use post-
processing software for data acquired using Innomar's parametric sub-bottom profilers
 Leica LiDAR Survey Studio (Leica LSS): is a state-of-the-art software tool for point cloud
generation and cleaning of raw LiDAR data
 HYPACK GEOPHYSICS: Software package designed for the acquisition and processing of sub-
bottom profiling, side scan, and magnetometer data
 SeaView MOSAIC: first post-processing and interpretation software capable of interactive mosaic
editing at full resolution, delivering high-resolution seafloor imagery with unmatched quality and using a
fraction of the time
6/6/2023 31

32. Bathymetr
y
The study of the "beds" or "floors" of water bodies,
including the ocean, rivers, streams, and lakes
The measurement of the depth of water in oceans, rivers, or
lakes. Bathymetric maps look a lot like topographic maps
Use lines to show the shape and elevation of land features
6/6/2023 32

33. Mapping the Seafloor Based on Four Principal Reasons
To learn about the deep parts of the ocean that
are hard to observe
To gather information about plate tectonics
To find shipwrecks and other items of interest
To aid in navigation
6/6/2023 33

34. Principles and Mechanisms of Bathymetric Survey
 Single-beam surveying: measures the water depth directly under the boat, generally
used for smaller water bodies.
Satellite-derived bathymetry (SDG): refers to the depths processed from optical
satellite imagery. SDB is based on the expectation that deeper water appears darker
than shallower.
Acoustic Doppler Current Profiler (ADCP): measure water velocity by transmitting sound
waves which are reflected off sediment and other materials in the water. Data collected from ADCPs can
then be used to for bathymetric mapping
 Sub-bottom profilers: most commonly used to view the layers of sediment and rocks under the
water body floor. A transducer sends a sound wave to the water body floor. This sound wave can
penetrate the water body floor. The data returned from the sound waves can be mapped to show the
layers beneath the water body floor.
6/6/2023 34

35. 6/6/2023 35
Single beam echo sounders (SBES),
also known as depth sounders or
fathometers determine water depth
by measuring the travel time of a
short sonar pulse, or “ping”.
The sonar ping is emitted from a
transducer positioned just below the
water surface, and the SBES listens
for the return echo from the bottom.
Single beam echo
sounders

36. 6/6/2023 36
The multi-beam echo
sounder send out a fan-
shaped sound pulse and
listens for a return from the
seafloor. The system then
calculates the time of return
and angle to determine
depth along the bottom; in
turn, giving us a 3D detailed
map of the seafloor shape.
This technology works very
similar to the way some
species use echolocation.
Multi-Beam Echo Sounders

37. 1.Bathymetric maps can help
scientists determine where fish
and other marine life feed, live,
and breed
1.Bathymetric data is also used
to create maps of coral habitats
to assist in conservation and
monitoring
1.Used for many research fields- flood
inundation, the contour of streams
and reservoirs, leakage, dam
removal, water-quality studies,
biological studies, planning the
coastal reservoir, etc.
1.Bathymetry also gives the
representation of underwater terrain,
and holds a very important role in
the hydrographic study of any water
body
Importance of
Bathymetry
6/6/2023 37

38. 6/6/2023 38
Hydrography
Vs
Bathymetry

39. Chapter 7+8
Chemistry Of Sea Water
& Dissolved Gas
6/6/2023 39

40. CONSTITUENTS OF SEA WATER
There are four different classifications of elements in seawater based
on their concentrations:
1. Hydrogen and Oxygen : make up most of seawater.
2. Major elements:
chloride (Cl−), sodium (Na+), sulfate (SO24−), magnesium
(Mg2+),
calcium (Ca2+), and potassium (K+).
3. Minor elements: inorganic phosphorus and inorganic nitrogen.
4. Trace elements: Fe, Mn, Mo, Zn, Co, Cu, and V.
6/6/2023 40

41. Elements Present in Sea Water
Forty-four elements are listed in and if we add hydrogen, oxygen we obtain a total of forty-
six elements that are known to occur in sea water.
Seawater chemistry shows 96.5% water and only 3.5% other elements.
Most abundant seawater element are sodium, chloride.
Elements in sea water are:
1.Major elements
2.Minor elements
and trace elements
6/6/2023 41

42. Major nutrient cycling
• Nutrients in the oceans are moved about by biological and physical processes.
• In the euphotic zone in the surface open oceans, nutrients are utilized mainly by
phytoplankton and cyanobacteria.
• In the deep sea, nutrients released back by decomposition of marine organisms.
• The major nutrients cycle in the oceans are considered to be
1. Nitrogen cycling
2. Phosphorus cycling
3. Carbon cycling
4. Silicon cycle
6/6/2023 42

43. NITROGEN CYCLING IN THE OCEAN
• Nitrogen gas (N2) from the atmosphere
dissolves into seawater at the ocean surface.
• Nitrogen fixation: Dissolved nitrogen gas is taken
up by just a few types microbes and convert nitrogen
into ammonium (NH4+).When microbes die, they
decompose, releasing ammonium into the
surrounding seawater.
• Nitrification: Some microbes convert ammonium to
nitrite (NO2-) and then nitrite to nitrate (NO3-).
• Remineralization: A host of organisms consume
particulate organic nitrogen and dissolved organic
nitrogen, converting some of the nitrogen back to
ammonium.
• Denitrification: To complete this complex cycle,
some microbes convert nitrate and nitrite back to
nitrogen gas.
6/6/2023 43

44. 6/6/2023 44

45. 6/6/2023 45
1. Weathering.
2. Absorption by
Plants.
3. Absorption by
Animals.
4. Return to the
Environment
through
Decomposition.
Phosphorus Cycle

46. Silica Cycle
6/6/2023 46
1. Silicon commonly occurs in nature as silicon dioxide (SiO2), also
called silica.
2. It cycles through the marine environment, entering primarily
through riverine runoff.
3. Silica is removed from the ocean by organisms such as diatoms
and radiolarians that use an amorphous form of silica in their cell
walls.
4. After they die, their skeletons settle through the water column,
and the silica redissolves.
5. A small number reach the ocean floor, where they either remain,
forming a silaceous ooze, or dissolve and are returned to the
photic zone by upwelling

47. 6/6/2023 47
Silica Cycle

48. 6/6/2023 48

49. Carbon Cycle in the Ocean
6/6/2023 49
Carbon gets into the ocean from the atmosphere in two ways.
In the first, air dissolves into the ocean surface. Winds and crashing
waves mix it into the upper half-mile or so, and because seawater is
slightly alkaline, the carbon dioxide is absorbed into the ocean.
The second involves the biologic pump. The ocean is a living medium
– it has algae and fish and whales, and when that organic material is
eaten or dies, it gets recycled. It rains down through the ocean and
makes its way to the ocean twilight zone, a level around 650 to 3300
feet (roughly 200 to 1,000 meters) deep.

50. 6/6/2023 50

51. 6/6/2023 51

52. Ocean
Acidification
6/6/2023 52
Ocean acidification is mainly caused by carbon dioxide gas in the
atmosphere dissolving into the ocean. This leads to a lowering of the
water's pH, making the ocean more acidic. Carbon dioxide is being
produced faster than nature can remove it, so increasing amounts
are being absorbed by the ocean.

53. D
I
S
S
O
L
V
E
D
G
A
S
Table: Percentage of gases in sea water and atmosphere
6/6/2023 53
Why is the ocean salty
?
Salt in the ocean comes from two sources:
1. Runoff from the land and
Rocks on land are the major source of salts dissolved in seawater. Rainwater
that falls on land is slightly acidic, so it erodes rocks. This releases ions that
are carried away to streams and rivers that eventually feed into the ocean
.
2. Openings in the seafloor (hydrothermal fluids)
which come from vents in the seafloor. Ocean water seeps into cracks in the
seafloor and is heated by magma from the Earth’s core. The heat causes a
series of chemical reactions. The water tends to lose oxygen, magnesium,
and sulfates, and pick up metals such as iron, zinc, and copper from
surrounding rocks.

54. 6/6/2023 54
Why the ocean is
salty ?

55. 6/6/2023 55
Why the ocean is
salty ?

56. 6/6/2023 56
Major dissolved Gases in Ocean
Table: 1 Gases Found in Seawater
Gas Percentage
by Volume in
Atmosphere
Percentage by Volume
in Surface Seawater
(salinity 35‰ and
temperature 20°)
Percentage
by Volume
in Ocean
Total
Nitrogen (N2) 78.08 48 11
Oxygen (O2) 20.99 36 6
Carbon
dioxide (CO2)
0.03 15 83
Other gases 0.95 1

57. THANK YOU
6/6/2023 57