Global Positioning Systems in the Classroom

Today we use a constellation of artificial stars provided by the Global Positioning System.

3 clear signals will provide you with accurate 2 dimensional position. A 4 th will give reasonably accurate elevation information.

Sources of GPS Errors Number of satellites visible — The more satellites a GPS receiver can "see," the better the accuracy. Buildings, terrain, electronic interference, or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. Number of satellites visible — The more satellites a GPS receiver can "see," the better the accuracy. Buildings, terrain, electronic interference, or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. GPS units typically will not work indoors, underwater or underground. GPS units typically will not work indoors, underwater or underground.

Sources of GPS Errors Satellite geometry — This refers to the relative position of the satellites at any given time. Satellite geometry — This refers to the relative position of the satellites at any given time. Poor geometry results when the satellites are located in a line or in a tight grouping. Poor geometry results when the satellites are located in a line or in a tight grouping. Ideal satellite geometry exists when the satellites are located at wide angles relative to each other. Ideal satellite geometry exists when the satellites are located at wide angles relative to each other.

Three things to keep in mind….

Avoid buildings and trees… They will weaken or block your signals

When trying to navigate… you must be moving to get accurate information… ?

Always remember that the GPS does not replace common sense. ALWAYS SHOW YOU THE STRAIGHT LINE ROUTE It will ALWAYS SHOW YOU THE STRAIGHT LINE ROUTE … BEST ROUTESAFEST ROUTE not the BEST ROUTE or the SAFEST ROUTE! A B

The Main Pages Every GPS displays its information on a set of main pages. These pages include: Main Menu Page Satellite Page Map Page Compass Page Position Page

MAIN MENU PAGES Garmin etrex Garmin 12 Garmin etrex Vista Garmin Etrex LEGEND

SATELLITE PAGES Garmin Etrex Garmin 12 Garmin etrex Vista Garmin 60 This is where we check if we have an adequate signal to use the GPS The outer circle is the horizon, the inner circle is a 45 o angle in the sky, and the dot in the centre is straight up. The numbers in the circle correspond to the numbers in the bar diagram Garmin Etrex LEGEND

MAP PAGES Garmin etrex Garmin 72 Garmin 60 TRAK MAPS Some GPS units come with maps, others require a map to be uploaded to the unit. Use the zoom option to change the scale of your map Use the pan option to look at the off-screen parts of the map *quit or esc gets you back Set your map to North Up or Track Up Garmin Etrex LEGEND

COMPASS PAGES Garmin etrex Garmin 12 Garmin 60 Garmin 60c This is the screen we use to navigate to a given waypoint On newer units, (including the LEGEND) you can manipulate the data fields to show what’s important to you The arrow will show you the direction to travel (straight line) The arrow is usually wrong if you are standing still – you have to be moving! Garmin Etrex LEGEND

POSITION PAGES On newer units, including the LEGEND your position is given right on the Satellite Page The accuracy of these coordinates will depend on satellite reception Position will likely be wrong if your map datum isn’t set properly Garmin etrex Garmin 12 Garmin etrex Vista Garmin 60 Garmin Etrex LEGEND

And finally…. Pick up your GPS!!

GARMIN ETREX LEGEND

POWER BUTTON…press and hold to turn on.

GARMIN ETREX LEGEND PAGE BUTTON…press to move through 5 screens.

GARMIN ETREX LEGEND SCROLL BUTTONS…move up or down menus

GARMIN ETREX LEGEND ENTER BUTTON…press to select an item.

GARMIN ETREX LEGEND THUMB STICK….press to enter, scroll, hold to mark.

Press and hold the power button until your GPS turns on… then press the PAGE button to get to the MAIN MENU.

Setup Menus The Setup Menu can usually be found on the Main Menu page. The setup menu is where you access all the various settings which you need to know about to properly operate your GPS. Newer units have more options. Lets Set our units…..(next slide) Garmin Etrex LEGEND

Setting your GPS Be sure to set the map datum to WGS 84 or the specific datum shown on the map you are using Set your Position Format (UTM or Lat/Long) Set the Units (metric or imperial) See the next slide for an example….

Navigation Setup Legend Position format: Set to UTM/UPS

Navigation Setup Legend Units: Set to Metric

Navigate to the MAIN MENU LEGEND: Go to FIND, Then WAYPOINTS Then NEAREST…

Navigate to the MAIN MENU LEGEND: Go to MARK, Then press the thumb stick.

Take both GPS units…. Take both GPS units…. lets go outside and try this… lets go outside and try this…