1. LAB 1 Navigation Coordinate System on Earth
Measuring Distance using Latitude and Longitude
Navigational Tools: Global Positioning System (GPS) & Nautical Charts

2. Latitude and Longitude
Imaginary lines divide the globe into degrees.
180° of longitude measure East and West
90° of latitude measure North and South

3. Degrees converted to Distance
1° = 60 minutes (′)
1′ = 60 seconds (″)
1° latitude = 60 nautical miles* (1 n mi = 1.15 st mi)
1 st mi = 5280 feet
1 n mi = 6072 feet
Example: A position located 20º N of the equator is how many nautical miles?
20º latitude x 60 n mi = 1200 n mi
1º latitude
*True on Mercator Projections, lines of longitude, the equator, and great circles.

4. Bearing
0º - 360º
If you were heading from point A to B your bearing would be (using True north):
30º NE A B

5. Using the Pythagorean Theorem to calculate distanceW b a c
City 2 (long, lat)
City 1 (long, lat)
a2 + b2 = c (a x a) + (b x b) = (c x c)
side a = difference between latitudes (y)
= latitude 1 – latitude 2
side b = difference between longitudes (x)
= longitude 1 – longitude 2
side c = √(a2 + b2)
= distance between City 1 and City 2

6. GPS
GPS is a satellite-based, radio-navigation network that provides fixes in all parts of the world day and night.
It is based on 26 satellites in circular orbits that are 10,900 miles above the earth’s surface.
At least 5 satellites are in “view” from one user system at any one time. Need at least 3.
Typical error:
position < 10 m
speed < 0.1 knots
Conditions affecting accuracy (reception):
Position of satellites will change slightly with time and affect accuracy
Overcast weather
Obstruction of satellite to receiver path by structures
Trees, buildings, etc.

7. Power and Keys

8. Data Screens & Course (NAV button)
Display terms:
Bearing = Where waypoint is relative to your position
Heading = Direction you are going
Speed = Speed over ground
Distance = Distance to waypoint

9. Saving Locations (Waypoints)
MENU
Highlight “Mark”
Press “Enter” to mark location
Press “Enter” to save waypoint
Use cursor and enter to create a waypoint name.

10. Using Nautical Charts for Navigation

11. Using Nautical Charts for Navigation – a closer view

12. Class Exercise
Use GPS to mark a location (latitude/longitude) on campus
Calculate distances between positions using longitude and latitude
Use Nautical charts for navigation