How To Understand The Inner Workings Of The GPS
By Stephen R. Goldsmith
Before I start in earnest, I need to state a disclaimer. Flightsim purists might not like what I have to say. Some like to navigate using VORs, NDBs, Intersections, and the like. Some like to navigate via the GPS. This tutorial deals with GPS-based navigation, and if you don't like using the GPS, there's nothing here for you.
For those of you that enjoy flying with the GPS but want to learn more about how to operate it, this is for you.
Part 1: The ButtonsMode: The Mode button allows you to change the way the that GPS presents its information. There are 3 modes available; the moving map display, the waypoint information display, and the route information display.
Direct To: The Direct To button (the little D with the arrow through it), brings up a display that allows you to select pretty much any airport or navigational aid (VOR, NDB or Intersection) and calculates a direct route to it. It also gives you access to the Emergency display, which lists the 20 closest airports and will calculate a direct route to the one you select.
Menu: This brings up a menu the allows you to change the look of the moving map display.
Arrows: The arrow buttons allow you to navigate the different menus and displays of the GPS as well as make selections in the different menus.
Enter: The Enter button confirms a selection. It is used with the Direct To displays and the Menu display.
Cancel: The opposite of the Enter button, the Cancel button cancels a selection or change.
Part 2: The Three Main DisplaysThe three main displays can be accessed by clicking the Mode button. You click the button to cycle through the displays.
Moving Map Display
Waypoint Info Display
Route Info Display
The Moving Map display is a graphical representation of where you are in relation to different airports, your intended course, different VORs, NDBs, Intersections, Jet and Victor Airways. It also gives you six basic points of information: 1. Your next waypoint; 2. Your groundspeed (in knots); 3. The distance to your next; Waypoint 4. Your current heading; 5. The bearing to your next waypoint; 6. The distance from your intended course (along with a left or right arrow to tell you which side of the course you're on).
One of your best friends will be the range rings displayed on the map display. There are three rings shown, the innermost being 5 miles, the middle being 10, and the outer being 20. You can use this to estimate your range to an airport or navigational aid with just a glance.
The Waypoint Information Display gives details concerning your next waypoint. I'm not going to repeat what was already said concerning the information at the top, as it is the same information as what was on the moving map display. There are four new pieces of information given in this display, though. You are given the ETE, or Estimated Time Enroute to your next waypoint, the ETA or Estimated Time of Arrival at your next waypoint, and your current Latitude and Longitude.
The Route Information Display gives details concerning
your entire route. You can use the up and down arrows to scroll
through your different waypoints. It displays the name of the
waypoint, the course from the previous waypoint and the distance
from the previous waypoint. You are also given four new pieces of
information, the Route ETE or the ETE for the entire route, and the
Route ETA and the Latitude and Longitude of your destination. This
display is great for getting an overall sense of how your journey
Part 3: The Direct To DisplaysThe two Direct To displays can be accessed by clicking the Direct To button, and it works exactly the same way as the Mode button.
The Direct To display allows you to select an airport or navaid and calculate a direct route to it. The top line of the display is your destination type. You can use the left and right arrows to cycle through the different types (Airport, VOR, NDB, and Intersection). Once you've selected a type, you can hit the down arrow to move on to the ID line. Hitting the down arrow once highlights the entire ID line. You'll want to hit the down arrow again, because by doing so you can highlight individual letters of the ID, making it much easier to select your destination. Once you have a single letter highlighted, you use the arrow buttons differently. Now the left and right arrows control which letter is highlighted and the up and down arrows allow you to cycle through different letters and numbers. Once you've got the ID in there, you should be able to confirm the name on the next line. You can also see your distance from, bearing to, and the latitude and longitude of your selected airport or navaid. Hit the Enter button and your GPS will now be set to guide you to where you want to go.
The Emergency display allows you to select an airport to divert to. It gives you the 20 nearest airfields (it's not an intelligent GPS, as it will show a 400 foot airfield even if you're in a 747, so be conscious of where you're diverting). As the name suggests, it's generally only used in emergencies, but it's a fun feature to experiment with. You're on a VFR flight and you want to stop and stretch your legs, highlight an airfield using the arrow buttons in this screen, hit enter, and you've got immediate directions to the airport you selected.
Part 4: The Menu DisplayMost of this is pretty self explanatory but I'll go over a few of the options. You select an option using the up and down arrows, you change an option using the left and right arrows, and you confirm your selection by pressing the Enter button. All of these are ease of use issues. Whatever works best for you is how you should set it.
The first option is the orientation of the map. You've got three choices for it. You can orient the map so north is up, you can orient it so your heading is up, and you can orient it so your planned route is up. I tend to keep it at north up because it's easier for me to keep my bearings straight.
The next six options are the self explanatory ones. It's exactly the same as if you're looking at the Map View. Airports are displayed pink, VORs displayed blue, NDBs displayed as pink circles, Intersections displayed as bluish-green points, Jet Airways as bluish-green lines, and Victor Airways as deep blue lines.
The Display Text On Map option concerns the heading, course, speed, and waypoint information displayed on the Map display. It toggles whether or not that is shown.
The Flight Plan and Track options are pretty self explanatory as well. The Flight Plan option displays your intended course in green, and the Track option displays the course you've actually taken in yellow.
The Display Range Rings option toggles, you guessed it, whether or not the Range Rings are displayed on the Map Display.
Final NotesA couple of final notes. As far as I can tell you cannot use the GPS to program different waypoints into a flight plan, you can only use the Direct To display to get direct routes. If you specify a flight plan when creating your flight, it will be loaded into the GPS. If you select a different route or airport, your flight plan is lost as far as the GPS is concerned. So be careful about changing your route if you're flying an IFR flight plan.
Knowledge of how the GPS works can be a great help in your simulated travels, and I sincerely hope I've helped make it clearer for some of you.