Lowrance 5200c 操作指南

 

6 

These  Custom Map Files (file format *.lcm) can also be shared be-

tween Lowrance GPS or sonar/GPS units and personal computers. This 

unit automatically reads Custom Map Files directly from the MMC or 

SDC. To use a custom map, all you need to do is slide an MMC contain-

ing a map into the GlobalMap. 

Well, now you know the basics of how the unit does its work. You might 
be ready to jump ahead to Section 2, Installation & Accessories, on page 

11, so you can mount your GlobalMap and plug in the power. Or you 

might want to see how our text formatting makes the manual tutorials 

easy to skim.  
If that's the case, move on to "How to Use This Manual" on page 8. But, 

if you want to understand the current state of satellite navigation, look 

over this segment describing how GPS and its new companion WAAS 

work together to get you where you're going. 
The Global Positioning System (GPS) was launched July 17, 1995 by 

the United States Department of Defense. It was designed as a 

24-hour-a-day, 365-days-a-year, all weather global navigation system 

for the armed forces of the U.S. and its allies.  
Civilian use was also available at first, but it was less accurate because 

the military scrambled the signal somewhat, using a process called Se-

lective Availability (SA). 
GPS proved so useful for civilian navigation that the federal govern-

ment discontinued SA on May 2, 2000, after the military developed 

other methods to deny GPS service to enemy forces. Reliable accuracy 

for civilian users jumped from 100 meters (330 feet) under SA to the 

present level of 10 to 20 meters (about 30 to 60 feet.) 
Twenty-four satellites orbit 10,900 nautical miles above the Earth, 

passing overhead twice daily. A series of ground stations (with pre-

cisely surveyed locations) controls the satellites and monitors their ex-

act locations in the sky.  
Each satellite broadcasts a low-power signal that identifies the satellite 

and its position above the earth. Three of these satellites are spares, 

unused until needed. The rest virtually guarantee that at least four 

satellites are in view nearly anywhere on Earth at all times.