Introduction to GPS Navigation

Introduction The Global Positioning System (GPS) is a free system available 24 hours a day, 365 days. Its an all weather outdoor system which provides users with: –Their position on Earth –Their height above sea level –Their speed and direction of travel –The time How it works –There is a network of 24 satellites orbiting earth. They each orbit earth twice a day and at any one time between 4 and 10 will be visible from your location. –The GPS system was developed by the US military. In the year 2000 the system was made public and more accurate when the “Selective Availability” SA was turned off.

GPS Satellites –1st satellite was launched in 1978 with the last being placed in 1994 –Have highly accurate clocks which transmit a microwave signal to earth. –On a cloudless night with minimal backlight the satellites can be seen orbiting the earth. GPS Receivers –The receivers take the information from the satellites and use triangulation to calculate the user's exact location. –A minimum of 4 satellites are needed for an accurate 3D position. The more satellites visible by the GPS, the greater the accuracy. –Accuracy is generally within +/- 10m, 95% of the time. –2 main brands – Garmin or Magellan Many different applications (Automotive, fitness, Outdoor, Marine, Aviation)

Features, Functions & Formats Features –Robust –Waterproof –Colour screen –Auto routing –Compass Functions –Maps –Sun/moon times –Tides –Geocaching –Trip data –Games –Altimeter –Calendar/calculator Formats –Distance, speed –Elevation –Time –Position –Datum

GPS Usage The most common use of the GPS receiver is to get a position fix. When your moving the gps gives you speed and direction of travel. Uses: Military & Civilian Missile guidance, Target tracking, Search & Rescue Aircraft, Vehicle, Human and Pet tracking Map making, Robotics, Surveying, Recreation Cold Start –The first time you use a GPS receiver or if you’ve moved more than 300km since you last used it. –May take up to 5 minutes to track satellites and initialise. Warm Start Receiver has recent navigational messages from satellites Up and running in less than a minute.

GPS Usage - Waypoints GPS receivers can store positional information as waypoints. These waypoints can be given names, labels, symbols etc. Can be stored or entered in one of two ways. –The current location of the GPS can be saved. (Mark) –A waypoint can be manually stored by entering coordinates or uploading them from a computer interface. Navigating to a waypoint –You can use the GPS to navigate to a waypoint using the “Go To” function. –The GPS will give you the distance and bearing to the waypoint which it continually updates as you move.

GPS Usage – Tracklogs & Routes Tracklogs –This is a breadcrumb trail of your travels, recorded on the GPS –The trackback function can be used to navigate back to a starting point using the tracklog. –It can be downloaded onto a computer to show where the GPS has been. Routes –It guides the user to a destination via a particular path –Similar to the “Go To” function –Many waypoints make up a route –Can create a route on mapping software and upload to GPS –GPS automatically follows the route, from one waypoint to the next GPS’s can save many different waypoints, routes and tracklogs depending on the make and model of the GPS.

Basic setup Main menu – Setup –System. Put gps in demo mode or normal. –Units. Put various “units of measure” to metric –Time. Set time and time format –Position format.Lat & Long or UTM/UPS Degrees-degress Degress-minutes-minutes Degress-minutes-seconds 17 fig Grid Reference –Map datumWGS 84 is a worldwide datum