Garmin gps Manual Do Utilizador
09/25/02
GPS_field_guide
8:19 A9/P9
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CHAPTER 1: INTRODUCTION TO GPS
1.1 What is GPS?
The Global Positioning System (GPS) is a system allowing to precisely identify locations
on the earth's surface.
on the earth's surface.
The GPS system has 3 parts (Figure 1):
· The Space segment: a network of 24 satellites placed into orbit (Figure 2). The first
GPS satellite was launched in 1978 and a full constellation of 24 satellites was
achieved in 1994. Each satellite is built to last about 10 years. Replacements are
constantly being built and launched into orbit.
achieved in 1994. Each satellite is built to last about 10 years. Replacements are
constantly being built and launched into orbit.
· The Control segment which consists of ground stations, located around the world that
make sure the satellites are working properly.
· The User segment: the GPS receivers used by the community (eg. ETrex device).
Figure 1 : The 3 GPS segments
This satellite-based system offers highly precise location data for any point on the planet,
in any weather conditions, 24 hours a day. It is mainly used for navigation, positioning
and other research applications.
in any weather conditions, 24 hours a day. It is mainly used for navigation, positioning
and other research applications.