Rand McNally rvnd-5510 用户指南

The Global Positioning System (GPS) is a constellation of satellites that a GPS 
receiver uses to calculate geographical positions. To determine a position, data 
from at least three satellites is required. To determine altitude, the data from 
four or more satellites is required. Accuracy of the positioning varies from 
10 feet to several hundred feet, depending on vehicle placement and the 
surrounding environment.

Geographical terrain (such as mountains), man-made structures (such as 
highway overpasses, bridges, and tall buildings), as well as weather can 
interfere with the GPS signal. For best GPS reception, position the TripMaker 
RVND and mount with a clear line of sight to the sky.

Some vehicles may have a limited view of the sky due to metal sun shields or 
a metallized windshield coating. If your unit does not appear to receive signals 
well inside your vehicle but works well outside, contact Rand McNally for an 
available external antennae.

Map data used by the TripMaker RVND includes the geographical coordinates 
for address locations and points of interest (POIs). With GPS reception, your 
device calculates a route to your selected location.