Lowrance 7200c 操作指南

Remember, the unit must have a clear view of the satellites in order to

receive their signals. Unlike radio or television signals, GPS works at

very high frequencies. These signals can be easily blocked by trees,

buildings, an automobile roof, even your body.
Like most GPS receivers, this unit doesn’t have a compass or any other

navigation aid built inside. It relies solely on the signals from the satel-

lites to calculate a position. Speed, direction of travel, and distance are

all calculated from position information. Therefore, in order for the

GlobalMap to determine direction of travel, you must be moving and

the faster, the better. This is not to say that it won’t work at walking or

trolling speeds — it will. There will simply be more "wandering" of the

data shown on the display.
GPS is plenty accurate for route navigation, but the U.S. Federal Avia-

tion Administration has special needs for aircraft traffic control that go

beyond basic GPS. The FAA has a program to boost GPS performance

even further with its Wide Area Augmentation System, or WAAS. This

GPS add-on will include a time control element that will help airliners

fly closer together while avoiding collisions. In addition to carefully

spacing airplanes along travel corridors, WAAS will eventually make

instrument landings and takeoffs more accurate as it replaces existing

aviation navigation systems.
Non-aviators can use WAAS signals to make their GPS navigation even

more accurate. Your unit receives both GPS and WAAS signals. How-

ever, WAAS has some limits you should know about.

WAAS can boost the accuracy of land GPS navigation, but the system

is designed for aircraft. The satellites are in a fixed orbit around the

Equator, so they appear very low in the sky to someone on the ground

in North America. Aircraft and vessels on open water can get consis-

tently good WAAS reception, but terrain, foliage or even large man-made

structures frequently block the WAAS signal from ground receivers.
You'll find that using your GPS receiver is both easy and amazingly

accurate. It’s easily the most accurate method of electronic navigation

available to the general public today. Remember, however, that this

receiver is only a tool. Always have another method of navigation avail-

able, such as a map or chart and a compass.
Also remember that this unit will always show navigation information

in the shortest line from your present position to a waypoint, regardless

of terrain! It only calculates position, it can’t know what’s between you

and your destination, for example. It’s up to you to safely navigate

around obstacles, no matter how you’re using this product.