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3
How Lowrance GPS Works
You'll navigate faster and easier if you understand how the GlobalMap
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 9. If you're new to GPS, read on, and
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 GlobalMap 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 uses an external 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 the GlobalMap 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™ 6 (This complete set of mapping data is
already installed on the GlobalMap 7300 and GlobalMap 9300.). Some
unit features — such as searching for businesses and addresses —
won't work without a custom MapCreate map. There is so much detail
in our background map (and even more in MapCreate) that we'll de-
scribe their contents and differences in Section 3, Basic GPS Opera-
tions, on page 29.
Another portion of the GlobalMap's onboard memory is devoted to re-
cording GPS navigation information, which includes waypoints, event
marker icons, trails and routes. This lets you look back the way you came.