Understanding Ocean Exploration
If you have ever driven a car or served as a “co-pilot” for one of your friends by directing him as he drives a car, you are
probably generally familiar with navigation on land. You may have said things like “Turn left when you reach the intersection”
or “Slow down! The speed limit here is only 25 mph.”
But navigation in the water is a little bit different. Ocean explorers use different units of measurements and speed and different
terminology to determine and describe their locations.
Where on Earth are you?
If your friend gave you a call and asked for your location, you might say “On the corner of 16 th St and Atlantic Ave” and your
friend would know where to find you.
To be more specific, you could tell a friend your “coordinates” or your location’s latitude and longitude. Any location on Earth
is described by these coordinates, which are actually two angles, measured in degrees called “minutes of arc” and “seconds of
arc”. These are denoted by the following symbols. o = degrees, ‘ = minutes, “ = seconds, so a location of 25o 40’ 1” means and
angle of 25 degrees, 40 minutes and 1 second. A degree is equal to 60 minutes of arc and a minute is equal to 60 seconds of arc.
1o = 60’, 1’ = 60”.
Latitude and Longitude (See Appendix III on pages 492 – 493 for review)
On the globe, lines of longitude are called “meridians” and extend from the north and south poles. The meridian that passes
through the former Royal Astronomical Observatory in Greenwich, England (now a museum) marks the 0o Longitude and is
known as the Prime Meridian. See Figure 1.
Lines of latitude run perpendicular to lines of longitude. Basically, lines of longitude are vertical (up and down) and lines of
latitude are horizontal (left and right). The Equator is 0o of latitude and is centered between the north and south poles. Lines
of latitude above the equator are indicated as north and lines of latitude below the equator are indicated as south. The farthest
north or south you can go from the equator is 90o. See Figure 2. While coordinates may not be practical for everyday
navigation (unless you use a GPS), oceanographers use them as part of their everyday system of navigation.
Figure 1: Lines of Longitude
Figure 2: Lines of Latitude
Telling Time
If you need to be somewhere at 3:00 pm, you probably use your watch or your cell phone to keep track of time so you know
when you need to leave. The time that you see on your clock or phone is known as the Local Time. Local time is a measure of
the position of the sun relative to a locality. At noon local time, the sun passes to the south and is furthest from the horizon in
the northern hemisphere. Basically, at noon, the sun is at its highest point in the sky.
But suppose we wanted to time and event that happens in space, like the time when the Mars rover Curiosity landed on Mars.
To do that, we need to establish a single universal time that isn’t based on your location on Earth. This is known as Universal
Time (UT) which refers to the “Coordinated Universal Time” scale. This time scale is determined by precise atomic clocks and
is kept by laboratories around the world, including the US Naval Observatory.
As you know, if you travel west toward California, you pass through different time zones. For each time zone you pass
through, going west, the local time is one hour earlier than the previous time zone. By the time you get to California, the local
time will be three hours “earlier” than local time on the east coast. So, if it’s 1:00 pm on the east coast, it’s 3 hours earlier on
the west coast, which means it will be 10:00 am.
The International Date Line is a special time zone boundary that mostly follows the meridian at 180o, directly opposite of the
Prime Meridian (0o longitude). The line ensures that we always match the correct date (day and time) at each location when
crossing time zones. Anyone crossing that line traveling from East to West, you gain (add) a day. If you are traveling West to
East and cross the IDL, you lose (subtract) a day.
Navigation terminology
Equator: The line of latitude at 0 degrees.
Prime Meridian: The line of longitude at 0 degrees that runs through Greenwich, England. It marks the starting point
of every time zone in the world.
International Date Line: A special time zone boundary, most of it following the line of longitude 180o.
Coordinated Universal Time (UTC): A single world-wide time system used for events that take place in space.
Longitude: The measurement of location east or west of the Prime Meridian, 0o longitude.
The farthest east or west from the Prime Meridian anyone can travel is 180o. 0o – 180 o East or West
Latitude: The measurement of location north or south of the equator, 0o latitude.
The farthest north or south you can travel from the equator is 90o. 0 o – 90 o North or South
Tropic of Cancer: The northernmost latitude at which the sun can appear directly overhead at noon.
It is located at 23.5o N latitude.
Tropic of Capricorn: The equivalent of the Tropic of Cancer but it is located at 23.5o S latitude.
Ship Terms
Bow: The front of the ship
Stern: The back of the ship.
Port: The left side of a ship when you’re facing the bow. Hint: “Port” and “left” both have 4 letters.
Starboard: The right side of a ship when you’re facing the bow.
Chronometer: A mechanical device for keeping time independent of ship’s motion that can be used to determine
longitude through celestial navigation.
Units of Measure
1 degree = 60 minutes
1 minute = 60 seconds
1 second = about 30 meters on the surface of the earth.
Distance and Depth measurements
Statute mile: Unit of length used to measure distance on land. 1 mile = 5280 feet
Nautical mile: A unit of measure used to measure distance over water.
1 nautical mile = 6067 feet. See visual above to compare a NM to a statute mile.
1 NM = 1 minute of latitude
Fathom: A unit of measure used to measure water depth. 1 fathom = 6 feet
Knot: The internationally accepted measure of maritime (a ship’s) speed. 1 knot = 1 nautical mile per hour
Name:
Date:
Block:
Understanding Ocean Exploration
Directions: Use the handout “Understanding Ocean Exploration” and a textbook to answer the
following questions.
Learning Target: Determine latitude and longitude of various locations.
1. What are the four cardinal directions?
,
,
,
2. Fill out the missing information on the diagram below.
B.
H.
E.
A.
C.
G.
F.
D.
3. What is the name of the diagram?
4. Which is longer, a statue mile or a nautical mile?
By how much?
5. Is Virginia Beach located east or west of the Prime Meridian?
6. Is Virginia Beach located north or south of the Equator?
7. The Titanic rests at a depth of about 12,500 feet.
a. How deep is that in miles?
b. How deep is that in fathoms?
8. Sperm whales can dive to depths over 1,000 meters.
a. How many fathoms is 1,000 meters?
b. What is a depth of 1,000 meters in statute miles?
c. What is a depth of 1,000 meters in nautical miles?
9. The deepest part of the ocean is the Challenger Deep at 35,840 feet which lies in the Mariana Trench.
a. How deep is that in statute miles?
Fathoms?
10. A NOAA Fishery Research Vessel (FRV) can travel up to about 10 knots.
a. How fast is this in terms of land speed in miles per hour?
b. What does NOAA stand for?
11. The average speed of a blue whale is 13 miles per hour.
Which is faster, the blue whale or NOAA FRV?
Explain your answer.
12. Label the parts of the ship.
D.
A.
B.
C.
13. You and your NOAA scientists are at 20o N latitude. Are you above or below the Tropic of Cancer?
14. How many nautical miles is it from the equator to 25o N latitude? Show work below
15. If a ship traveled from 76o N to 20o S latitude, how many nautical miles would that be? Show work!!!
16. If it’s 10 pm on Monday, and a ship is traveling west and crosses the IDL, what is the time and day?
17. For each LETTER on the map, give the latitude and longitude.
Indicate which body of water or continent each point is located.
Point
Latitude
Longitude
Location???
Body of water/ Continent
A
B
C
D
E
F
G
H
I
J
18. Which direction would you travel to go from point G to point J?
19. Which point is located 60o S and 40o W of point E?
20. Indicate the degrees and direction you would travel to get from point D to point F?