You can replay this sonar log in the unit using the Sonar Simulator func- tion. You can save several different sonar log files, erase 'em and record new ones, over and over again.
How Your GPS Works
You'll navigate faster and easier if you understand how this unit scans the sky to tell you where you are on the earth — and, where you're go- ing. (But if you already have a working understanding of GPS receivers and the GPS navigation system, skip on ahead to Section 2, Installation
&Accessories on page 13. If you're new to GPS, read on, and you can later impress your friends with your
First, think of your unit as a small but powerful computer. (But don't worry — we made this unit easy to use, so you don't need to be a com- puter expert to find your way!) The unit includes a keypad and a screen with menus so you can tell it what to do. The screen also lets the unit show your location on a GPS plotter, as well as point the way to your destination.
This unit uses an internal antenna/receiver module, which makes the whole system work something like your car radio. But instead of your favorite dance tunes, this receiver tunes in to a couple of dozen GPS satellites circling the earth. (It will also listen in to the WAAS satellites in orbit, but more about that in the upcoming segment introducing you to GPS and WAAS.)
Your unit listens to signals from as many satellites as it can "see" above the horizon, eliminates the weakest signals, then computes its location in relation to those satellites. Once it figures its latitude and longitude, the unit plots that position on the GPS screen. The whole process takes place several times a second!
Another portion of the unit's onboard memory is devoted to recording GPS navigation information, which includes waypoints, event marker icons, trails and routes. This lets you look back the way you came, and retrace your path.
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