GLY150: INTRODUCTION TO OCEANOGRAPHY University of North Carolina Wilmington

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Lecture Outline

Seafloor Mapping

I. Seafloor Mapping

A.  Coordinate System

1. Latitude

a.  Angular distance or degrees of arc from the equator
b.   180°, 90°S - 0 - 90°N
c.   Points at the same latitude on a sphere are drawn as parallels

2.  Longitude

a.  Angular distance or degrees of arc from the Prime Meridian, 0°
b.  360°, 180°W - 0 -180°E
c.  Points at the same longitude on a sphere are drawn as meridians

B.  Projection of the Earth's surface

1.  Mercator

a.  Cylindrical
b.  Tangent at the equator
c.  Large distortion at the poles
d.  Lines drawn between two points have true azimuths

C.  Navigation

1.  Celestial

a.  North Star
b.  Southern Cross
c.  Measure the angle between horizontal and location of star overhead to determine latitude

2.  Chronometer

a.  Essentially a clock not affected by ships motion
b.  Set to time of sun's zenith at Prime Meridian, 0°, Greenwich England
c.  Measure time of zenith relative that at the Prime Meridian to determine longitude

3.  Global Positioning System (GPS)

D.  Techniques for Determining Bathymetry/ Physiography of Ocean floor

1. Lead line

2. Echo sounders

a. High frequency

1. multibeam swath systems
2. sidescan sonar systems

b. Low frequency

1. seismic profilers

3. Satellite altimetry

4. Underwater cameras, videos mounted on submersibles, remotely operated vehicles (ROVs)

Some helpful links relevant to these lectures:

National Deep Submergence Facility
Seafloor Topography from Satellite Altimetry
WHOI's Underwater Vehicles
Global Positioning System

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