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

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

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.

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

Using the Pythagorean Theorem to calculate distance W b a c City 2 (long, lat) City 1 (long, lat) a2 + b2 = c2 (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

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.

Power and Keys

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

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.

Using Nautical Charts for Navigation

Using Nautical Charts for Navigation – a closer view

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