1. Latitude
The equator is the reference line.

2. Latitude is an Angular Distance

3. Lines of Latitude are Parallels

4. Finding Latitude Using the Altitude to Polaris
The angular distance of any celestial object above the horizon.
This is the angle between an observer’s line of sight and the horizon.
The maximum altitude of any object is 90o.
Directly above the observer.
Called the zenith.

5. Using a Sextant to find the Altitude of a Celestial Object

6. Altitude of Polaris 90 o 90 o

7. Altitude of Polaris
60o 60 o

8. Altitude of Polaris
30o
30o

9. Altitude of Polaris 0o

10. Finding Polaris Using the Big Dipper

11. Finding the South Pole of the Sky using the Southern Cross
The Southern Cross is used to find south. It has five stars.
Visualize a line extending from the long axis.
You can find south by estimating a distance that is about five times that of the two pointer stars along that line. You can also estimate this distance by using three hand widths as shown in the illustration. South is below the south pole of the sky.

12. Finding the South Pole of the Sky using the Southern Cross
You can also imagine a line connecting the two pointer stars.
Divide this line in half and then visualize another line extending at 90o.
Extend an imaginary line extending from the long axis of the Southern Cross.
The two lines will meet in the approximate position of the south pole of the sky.

13. Longitude
Measured east or west of the Prime Meridian

14. The Prime Meridian Reference line for longitude
Runs north-south through the Royal Observatory in Greenwich, England
Established at the International Prime Meridian Conference
October, 1884 in Washington, D.C.
France didn’t adopt it until 1911
The Royal Observatory in Greenwich, England

15. Longitude
Angular Distance East or West of the Prime Meridian

16. Meridians Half Circles Trend North to South Converge at the poles.
True North is where meridians converge at the north geographic pole/

17. Magnetic North is not the same as True North
Magnetic North is the direction in which Earth’s magnetic lines of force converge

18. Magnetic North
Magnetic North is not in the same location true north and moves 10 to 40 km per year
It’s currently about 1,000 km from the true North Pole, in Hudson Bay, Northern Canada (at 82.7o N, 114.4o W in 2005).

19. Compasses Are Unusable Near the North Pole
The horizontal force of the magnetic field
Responsible for the direction in which a compass needle is oriented
Decreases in strength as it approaches the North Magnetic Pole, where it is zero.
Close to the pole, an area is reached where the frictional forces in the pivot are comparable to the horizontal forces of the magnetic field.
The compass starts to behave erratically
Eventually, as the horizontal force decreases even more, the compass becomes unusable

20. Magnetic Declination
The difference in degrees between magnetic north (indicated on a magnetic compass) and true north.
Because magnetic north is continually changing, this is good only for the year of the map.

21. Magnetic Declination West Declination East Declination Agonic Line
(No Declination)

22. Using Latitude and Longitude to Locate Positions on Earth

24. Equator Prime Meridian Tropic of Cancer (23.5o N)
Tropic of Capricorn (23.5o S)
Prime Meridian
50o S, 75o W

25. Time Zones

26. Earth’s Rotation
Earth spins on it’s axis, the imaginary straight line through Earth between the North Pole and the South Pole
The axis of rotation is inclined 23 ½ degrees from a perpendicular to the plane of Earth’s orbit.

27. Rate of Earth’s Rotation
Earth makes one complete turn from west to east every 24 hours.
Angular Rate of Rotation: One complete rotation is equal to 360 degrees in 24 hours or 15o/hr.

28. Night
Day
As you travel west to east, time is later

29. Time Zones of the World Time Zones cover 15 degrees of longitude
There is a one hour time change for every 15 degrees (time zone)

30. Standardizing Time
Many observations are given in terms of time at the Prime Meridian which is referred to as:
Greenwich Mean Time (GMT)
Zulu Time (Z)
Universal Coordinated Time (UTC)

31. The International Date Line
Approximated by the 180o meridian
Adjusted to pass around islands
When crossed the calendar date changes
When crossed from west to east
One is subtracted from the calendar date
When crossed from east to west
One day is added to the calendar date
The sun time is unchanged
Friday Thursday
International
Date Line

32. Expressing Time The 24-hour Clock
Begins at midnight and ends 24 hours later
Hours and minutes
7:30 a.m.
07h25m or 0725
3:15 p.m.
1515
12 noon
1200

33. What is Noon and Midnight?
1200 hours
p.m. starts after this at 12:00:01
Midnight
0000 hours
a.m. starts after this at 00:00:01

34. Finding Time The difference in Sun Time
15 degrees of longitude corresponds to a time difference of one hour
Take the difference in longitude between two locations and divide by 15o

35. Example 1 Find the time in Denver if the time at Greenwich is 1400
Longitude of Greenwich is 0o
Longitude of Denver is 105o West
Difference in longitude is 105o
105o/15o = 7 hour time difference
Denver is west so it’s earlier than Greenwich
Time at Denver is 0700

36. Problem (Lab p.6)
Location A has a longitude of 135o W and location B has longitude of 32o E.
If the “Sun” time at A is 1735 (5:35 p.m.) on March 10, what is the “Sun” time and date at location B.

37. *Traveling west from 135o would be a difference of 193o
Problem (Lab p.6)
Step 1
Determine the smallest difference in longitude between the two locations.*
135o + 32o = 167o
135o W
32o W
*Traveling west from 135o would be a difference of 193o
135o to 180o = 45o and 180o to 32o = 148o
45o + 148o = 193o

38. Problem (Lab p.6) Step 2 Find the time difference
Divide the difference in longitude by 15o
167o/15 = hours
Find how many minutes 0.13 hours represents by multiplying 0.13 by 60 (there are 60 minutes in an hour
0.13h x 60 min = 7.8 (8 minutes)
The time difference is 11h08m.

39. Problem (Lab p.6)
Determine if the time at B is later or earlier than at A
Location B is East of Location A
This makes the time a B later than at B
Add the time difference to the “Sun” time at A
 11h08m (5:35 p.m.)
 h takes us to 0435 (4:35 a.m.) and into the next day
 Add the additional 8 minutes to 4:35 a.m.
The time at B is 04h43m on the next day which is March 11.

40. The Statute Mile
One degree of latitude is equal to approximately 69 statute miles
A statute mile is 5,280 feet.
The term mile was first used by the Romans (statute mile for land mile).
Was about 1,000 paces
The term “Mile” is derived from the Latin Words “milia passuum” for 1,000 paces
Was defined by an act of Parliament in 1592 during the reign of Queen Elizabeth I.

41. The Nautical Mile 1 arc minute of latitude = 1 nautical mile
One degree = 60 minutes = 60 nautical miles
Examples converting latitude to nautical miles . . .

42. Example 1 10 degrees of latitude = ? Nautical miles
10o x 60 min = 600 minutes
1 min of lat. = 1 nm
(1 min) X = (600 min)(1 nm) = 600 nm 1o
600 min X
(1 min)
(1 min)

43. Example 2 8o 30’ (8.5o) of latitude = ? Nautical miles
8.5o x 60 min = 510 minutes
Ans nm 1o

44. Converting Statute Miles to Nautical Miles
1 degree of latitude = 69 statute miles (mis)
Remember that 1 minute = 1 nautical mile (nm)
Therefore: 60 min = 69 mis
1 nautical mile = 1.15 statute miles
60 nm nm X = (69 ms) (1nm)
69 mis X nm =
X = 69 mis 60
= 1.15 mis

45. Converting Nautical Miles to Statute Miles
125 nautical miles is equivalent to how many statute miles?
1 nm nm X = (1.15 mis)(125 mn)
1.15 mis X nm =
X = (1.15 mis)(125) = mis
125 nautical miles  144 statute miles

46. Converting Statute Miles to Nautical Miles
144 statute miles is equivalent to how many nautical miles?
1 nm X X = (1 nm)(144 ms)
1.15 mis mis mis =
X = 144 nm = 125 nm
1.15
144 statute miles = 125 nautical miles

47. The Knot Unit used for the speed of a vessel relative to a fluid
Ships in water
Airplanes in air
One knot = one nautical mile per hour
Abbreviations:
kt (singular)
kts (plural)
kn (Used by the International Hydrographic Organization)

48. Origin of the term “Knot”
Until mid 19th century the “chip log” was used.
A wooden panel, attached to a line was cast over the ship’s stern
Knots placed in the rope, spaced at 47’ 3” passed through a sailor’s hands
Another sailor used a 30 second sand-glass to time the operation
1 knot = inches per second

49. Global Positioning System (GPS)

50. Global Positioning System (GPS)

51. Triangulation using GPS