4
How Lowrance GPS Works
You'll navigate faster and easier if you understand how the GlobalMap
5300c 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 Sec-
tion 2, Installation & Accessories on page 11. If you're new to GPS, read
on, and you can later impress your friends with your new-found knowl-
edge.)
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 GlobalMap 5300c 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 GlobalMap 5300c 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 GlobalMap 5300c figures its
latitude 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.
The background map is suitable for many navigation chores, but for
maximum accuracy and much more detail, you need our optional map-
making software, MapCreate™. Some unit features — such as search-
ing for businesses and addresses — won't work without a custom Map-
Create map. There is so much detail in our background map (and even
more in MapCreate) that we'll describe their contents and differences
in Section 3, Basic GPS Operations, on page 34.
Another portion of the GlobalMap 5300c'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.
Think of this data storage like the hard drive memory in a computer or a
tape in a cassette tape recorder. You can save several different GPS data
