Eagle Electronics 642c iGPS manual How GPS Works

NOTE:

The above memory capacities refer only to the IntelliMap 642c's on- board memory. The amount of GPS data you can record and save for recall later is limited only by the number and size of MMC cards you have.

NOTICE!

The storage temperature range for your IntelliMap 642c is from -4 degrees to +167 degrees Fahrenheit (-20 degrees to +75 degrees Celsius). Extended storage in temperatures higher or lower than specified will damage the liquid crystal display in your unit. This type of damage is not covered by the warranty. For more informa- tion, contact the factory's Customer Service Department; phone numbers are listed on the last page of this manual.

How GPS Works

You'll navigate faster and easier if you understand how the IntelliMap 642c scans the sky to tell you where you are on the earth – and, where you're going. (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 11. If you're new to GPS, read on. You can later impress your friends with your new-found knowledge.)

First, think of your unit as a small but powerful computer. (But don't worry — we made it easy to use, so you don't need to be a computer ex- pert to find your way!) The IntelliMap 642c 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 moving map, as well as point the way to your destination.

This gimbal-mounted IntelliMap 642c uses an internal an- tenna/receiver module, which makes the whole system work something like your car radio. But instead of your favorite dance tunes, this re- ceiver 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 the IntelliMap 642c figures its lati- tude and longitude, it plots that position on the moving map shown on the screen. The whole process takes place several times a second!

The performance doesn't stop there. Stored in the permanent memory of each unit is a basic background map of the entire world. We lock it in here at the factory — you can't change or erase this map.

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