This document provides an overview of key concepts for navigation including: - The terrestrial coordinate system uses latitude and longitude to determine positions on Earth - Key reference points include the poles, equator, prime meridian and meridians which divide Earth into longitude lines and latitude circles - Positions are specified with degrees, minutes, and seconds of latitude and longitude - Time zones are based on meridians and adjusted for daylight saving time and international date lines

1. NS100 Introduction to Navigation and Time

3. Reference Points and Lines Axis Poles Great Circles Equator Meridians Small circles

4. Reference Points

5. Prime Meridian

6. Equator North Pole South Pole Longitude line Latitude line

7. Coordinate System Position - L atitude and Longitude Example: Degrees o Minutes’ Seconds” 39 o 58’ 55” N 075 o 28’ 45” W

8. Rhumb Lines & Great Circles Rhumb line Great Circle

10. Time

16. Equator - - - - - - - - - - - X W V U T S R Q P O N Z A B C D E F G H I K L 11 10 9 8 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 10 11 + + + + + + + + + + + +12 Y -12 M

17. +12 +11 +10 +9 +8 +7 +6 +5 +4 +3 +2 +1 0 -1 -2 -3 - 4 -5 -6 -7 -8 -9 -10 -11 -12 Y X W V U T S R Q P O N Z A B C D E F G H I K L M

18. Time Definitions Daylight Savings Time – SPRING AHEAD , FALL BACK +5 becomes… +4 -9 becomes… -10

19. International Date Line Used as a convenience. “ If its SUN day in SAN Francisco, it’s MON day in MAN illa”

21. Date Time Group Format Date Time Group (DTG) - This format is used on virtually all military message traffic. The format is as follows: DDTTTT Z MONYR 241300ZJAN04

22. Arc to Time Conversions ARC TIME 15 deg 1 hr 1 deg 4 min (1 deg =60’) 60’ 240 sec (1min=60sec) 1’ 4 sec