108

Question 1

What is the aim of the OS108 module?

Answer 1

To introduce key concepts in ocean exploration, hydrography, and the geomorphological structure of the marine environment.

Question 2

Define Hydrography.

Answer 2

Hydrography is the science of measuring and describing physical features of water bodies and adjacent land areas.

Question 3

List the applications of Hydrography.

Answer 3

• Safe navigation
• Economic development
• Security & defense
• Scientific research
• Environmental protection

Question 4

Name a major contributor to hydrography.

Answer 4

National Geospatial-Intelligence Agency

Question 5

What are the areas of application for Hydrography?

Answer 5

• Ocean Exploration
• Coastal Ecology Surveys
• Oil & Gas Industry
• Dredging Operations
• Ports & Harbors
• Navigation
• Seabed Classification

Question 6

What branches of knowledge contribute to Hydrography?

Answer 6

• Mathematics & Physics
• Waves & Currents
• Acoustics & Optics
• Geodesy & Positioning

Question 7

What are the types of instruments used in Hydrography?

Answer 7

• Optical Instruments & GPS
• Acoustic Instruments
• Remote Sensing Technologies
• Measurement Platforms

Question 8

What does GNSS stand for?

Answer 8

Global Navigation Satellite System

Question 9

What are the three main segments of GNSS?

Answer 9

• Space Segment
• Control Segment
• User Segment

Question 10

Name a major GNSS system.

Answer 10

GPS (NAVSTAR)

Question 11

What is trilateration in GNSS?

Answer 11

Determining the distance from a user to multiple satellites to calculate location.

Question 12

How is distance to satellites calculated?

Answer 12

Distance = Velocity × Time

Question 13

What are common sources of errors in GNSS positioning?

Answer 13

• Timing inaccuracies
• Ephemeris errors
• Atmospheric delays
• Multipath errors
• Intentional errors
• Receiver noise

Question 14

What is Differential GPS (DGPS)?

Answer 14

A system that improves accuracy by using a reference station to correct errors.

Question 15

What does DOP stand for in GNSS?

Answer 15

Dilution of Precision

Question 16

What is Geodesy?

Answer 16

The science of measuring and understanding the Earth’s geometric shape, gravity field, and orientation in space.

Question 17

Describe the shape of the Earth.

Answer 17

The Earth is not a perfect sphere but an ellipsoid.

Question 18

What is the difference between geoid heights and ellipsoid heights?

Answer 18

Geoid heights are orthometric heights measured from mean sea level, while ellipsoid heights are measured from a mathematical reference surface.

Question 19

What is a geodetic datum?

Answer 19

A reference system for positioning.

Question 20

What are the types of map projections?

Answer 20

• Conformal Projections
• Equal-Area Projections
• Equidistant Projections

Question 21

What is a spring tide?

Answer 21

Tides that occur during the New and Full Moon phases when lunar and solar forces align.

Question 22

What are neap tides?

Answer 22

Tides that occur during the First and Last Quarter Moon phases when lunar and solar forces are at quadrature.

Question 23

What is the purpose of Admiralty charts?

Answer 23

To graphically display bathymetry and provide additional navigation information.

Question 24

What are principal tide-raising constituents?

Answer 24

• M2
• S2
• K1
• O1

Question 25

What is the UK’s Ordnance Datum Newlyn (ODN)?

Answer 25

A reference based on average sea level measurements from 1915 to 1921.

Question 26

What is the relationship between tidal currents and geomorphology?

Answer 26

Tidal currents are influenced by features such as sand banks, coastlines, and estuaries.

Question 27

What are the types of environments in hydrographic measurements?

Answer 27

* Intertidal * Coastal * Deepwater

Question 28

What are heights for land areas referenced to?

Answer 28

Mean High Water Springs (MHWS) ## Footnote Heights are given in meters.

Question 29

What are drying heights displayed in?

Answer 29

Meters and decimeters, referenced to Chart Datum ## Footnote Drying heights are underlined.

Question 30

What is the purpose of hydrographic approaches?

Answer 30

To map the seafloor and position objects underwater.

Question 31

Define intertidal environments.

Answer 31

Areas between high and low tide.

Question 32

What is a coastal environment?

Answer 32

Shallow areas near land.

Question 33

What are deepwater environments?

Answer 33

Deeper areas of the ocean.

Question 34

What factors influence the choice of hydrographic techniques?

Answer 34

Goals, budget, time, and required resolution.

Question 35

What does LIDAR measure?

Answer 35

Distance to the seafloor using pulsed laser light.

Question 36

What is a limitation of LIDAR?

Answer 36

Limited by water turbidity.

Question 37

What is photogrammetry used for?

Answer 37

Creates 3D models from photographs.

Question 38

What does a Single Beam Echo Sounder (SBES) do?

Answer 38

Sends sound pulses directly down to measure depth.

Question 39

How does a Multibeam Echo Sounder (MBES) differ from SBES?

Answer 39

Measures depth over a swath, providing wider coverage.

Question 40

What is sidescan sonar used for?

Answer 40

Maps the seabed by measuring reflected sound.

Question 41

What does sub-bottom profiling measure?

Answer 41

Layers below the seabed.

Question 42

What is the role of magnetics in hydrographic surveys?

Answer 42

Measures magnetic anomalies in the seafloor.

Question 43

What does high resolution in hydrographic surveys depend on?

Answer 43

More sensors/equipment and longer survey durations.

Question 44

What is the purpose of seismic techniques?

Answer 44

To provide detailed views of layers below the seabed.

Question 45

What is the principle of acoustic techniques?

Answer 45

Transmit sound pulses, measure return time to calculate depth.

Question 46

Define gross errors.

Answer 46

Human errors or blunders in measurement or calculation.

Question 47

What are systematic errors?

Answer 47

Predictable errors arising from observational, environmental, or instrumental flaws.

Question 48

What are random errors?

Answer 48

Unpredictable, generally small errors following a normal distribution.

Question 49

What is a time series?

Answer 49

A sequence of data points recorded at successive time intervals.

Question 50

What do measures of central tendency include?

Answer 50

* Mean * Median * Mode

Question 51

What does variance measure?

Answer 51

Variability of the signal around the mean.

Question 52

What is the standard deviation?

Answer 52

The square root of variance.

Question 53

What does the root mean square error (RMSE) indicate?

Answer 53

The average of the squared differences between observed and predicted values.

Question 54

What is a moving average used for?

Answer 54

To reduce noise in a time series.

Question 55

What is habitat mapping?

Answer 55

Understanding the physical condition and biodiversity of marine environments.

Question 56

What percentage of assessed areas in the Greater North Sea and Celtic Seas are physically disturbed?

Answer 56

86%.

Question 57

What are the key activities in benthic habitat mapping?

Answer 57

* Mapping spatial extent of habitats * Species classification/enumeration

Question 58

What are invasive methods in habitat mapping?

Answer 58

* Grabs * Dredges/Bottom-Trawls

Question 59

What does the use of multibeam echosounders provide?

Answer 59

Detailed information on water depth and seabed morphology.

Question 60

What is a challenge in habitat mapping?

Answer 60

Balancing qualitative descriptions with quantitative measurements.

Question 61

What is the significance of tracking macrofauna?

Answer 61

Monitoring movement and behavior of larger marine species.

Question 62

What is the impact of climate change on marine species?

Answer 62

Shifting distributions, especially plankton, due to rising sea temperatures.