History of Oceanography II

September 2008

Text Website: www.mhhe.com/sverdrup9e

Navigational Tools

Latitude/Longitude Chronometer

Astrolabe, Sextant, and Chip Log Charts/Maps Compasses Echo Sounders Satellites

Latin root “navis” and “agere” “to move or direct”

Finding Latitude at Sea

Used the altitude of the North star and the angle of the ship The angle of degrees what the

latitude of the ship Celestial Navigation

Finding Longitude

Chronometer (1773) Time piece that wasn’t affected by gravity

Invented by John Harrison Used the difference in time of day from start to

current position Normal Pendulum clocks lost 10 minutes per day

Off course by 150 miles or more (242 km) James Cook used Chronometer to circumnavigate

the globe (1779) New Charts of the World

1884 Prime Meridian made 0° Longitude through Greenwich, England

15° = 1 hour

The longitude is directly related to the difference between true local time and Greenwich time: 1 hour time difference = 15 degrees longitude difference

                            

    Harrison's H1 (built 1729-36). Height 76 cmWeight 36 kgMost of the wheels are made of woodAccurate to within a couple of seconds per day

                                Harrison's Watch H4 Completed in 1759On two trials across the Atlantic, it determined the longitude within 10 nautical miles

H1

H3H4

Harrison’s Chronometers

Mariner’s Compass

Early form of the magnetic compass Formed 32 points

Mariners thought that compass was wrong Didn’t understand magnetic variation of

compass at the time Angle between magnetic north and true north

Used to determine where wind was coming from when sun was down

Early Chinese first to use compass ~1040 AD Loadstone/Magnetite

Diagram of a Ming dynasty mariner's compass

Nautical Maps/Charts

~ 13th Century Emergence of Maps and Charts of open water

Ptolemy’s map 127 AD Polynesian Stick Maps

Ptolemy's World Map - 150AD

Charting Currents

1777 Benjamin Franklin Gulf Stream Map

1806 Matthew Maury Father of Modern Oceanography US Navy Cataloged wind and currents of ocean

1855 Wrote: The Physical Geography of the Sea

Astrolabe, Sextant, and Chip Log

Astrolabe Dates back to

Greece Helped to tell

time ~ 15 Century

Used to determine latitude

Altitude of the stars was taken

Angle

                                                                                               

                                     

Astrolabe in use.For a sun sight, the astrolabe was allowed to hang freely and the alidade was adjusted so that a ray of sunlight passed through the hole in the upper vane and fell precisely on the hole in the lower vane.

Sextant/Quadrant

1730 Independently Invented John Hadley (English) Thomas Godfrey (American)

More accurately measured the angle of horizon and stars More accurate latitude

Chip Log

Speedometer Line containing knots at intervals Counted knots over time

Gyroscopic Compass

1907 to present Points always to True North Not affected by metal on hull of ship Uses electricity power

Soundings

Before soundings, ocean floor thought to be featureless

Used hand lines with weights to find depth and features of ocean floor

Challenger expedition Canon ball with piano wire

Made determining touch easier 1895, only 7000 soundings of deep

ocean had been made (2000 m or greater)

Echo Sounders

~ 1914 World War I Determines Ocean floor Depth Uses Reflection of Sound waves

Primitive sonar 1925 German ship Meteor

Charted ocean depth and discovered the mid-Atlantic ridge

1950’s first detailed chart of ocean floor

Satellites

1978 NASA launches Seasat Sea-surface temperature Surface wind speed and direction Directional wave spectra Satellite included

Radar altimeter Wind field scatterometer Microwave radiometer Radiometer operating in visual and infrared

1992 US/France Launch TOPEX/Poseidon Ocean circulations interaction with the

atmosphere

Radar Altimeter

MicrowaveRadiometer

The Future

Private/institutional and national oceanographic institutions Observing process that

take place Looking at ocean basins

with observatories Using ROV and AUV

Science of the Deep

GPS: Global Positioning System

Global Navigation Satellite System (GNSS)

Uses 28 earth orbiting satellites, 11,000 mi above Earth, 12 hour orbit around Earth Location Speed/Direction Time

Citations

http://waterencyclopedia.com/Mi-Oc/Navigation-at-Sea-History-of.html

http://www.riverdell.k12.nj.us/staff/molnar/onotesch1.htm

http://en.wikipedia.org/wiki/Compass http://www.mat.uc.pt/~helios/Mestre/Novemb00/

H61iflan.htm http://www.allstar.fiu.edu/aero/GSI.htm http://pubs.usgs.gov/gip/dynamic/developing.html http://adsabs.harvard.edu/abs/1978BoLMe..13..393D http://en.wikipedia.org/wiki/Global_Positioning_System http://www.howstuffworks.com/gps.htm 1557 sailors using instruments of navigation.. IRC. 2005.

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