What is GPS?
GPS or Global Positioning System is a system of satellites
created and maintained by the U.S. Department of Defense
and used for worldwide navigation. The GPS project
began in the late 1970s for the military but was deregulated
for public use in the 1980s. At any given time, there
are 24 GPS satellites orbiting the Earth transmitting
high frequency radio waves back to the surface. Each
satellite orbits the Earth twice in one day and is
monitored by terrestrial control stations. This network
of control stations, called WAAS or Wide Area Augmentation
System, was initiated by the U.S. Federal Aviation
Administration to increase the accuracy of global positioning.
An additional feature of GPS called DGPS or Differential
GPS was incorporated by the U.S. Coast Guard for precision
Garmin iQue 3600
Handheld GPS Receiver
GPS is free to the public and doesn't require any
initial set up charges. To access the system, you need
a GPS receiver to translate the code to geographical
information. Due to security issues, GPS operates on
two different types of code–C/A Code (Coarse/Aquisition
Code) and P-code (Precise Code). The C/A Code is for
public use and is less accurate than encrypted P-code
for military use. Generally, GPS signals are limited
in that they lack the ability to pass through buildings
GPS Technology at Work
Opening GPS to the public has created a market surge
of GPS compatible devices for consumer use. In addition
to GPS receivers, many personal electronics such as
cellular phones, PDAs, and automotive navigation systems
utilize GPS technology. Software packages with GPS
locators are also available to convert your personal
computer into a GPS receiver.
Calculating locations by a triangulation method,
GPS receivers map a 2D position (latitude and longitude)
from at least three satellite signals and a 3D position
(latitude, longitude and altitude) with four or more
satellites. Incorporated with WAAS, a location can
be determined within three meters versus a hundred
meters via satellite alone.
How information from a GPS receiver is displayed
varies among devices. Some units have color LED screens
for detailed street and terrain maps while others only
use a plotter system to track a route. If you are investing
in a GPS device, here are some recommended features
to look for:
Lowrance iWay 500c
1. WAAS Capability. A GPS device that utilizes
WAAS increases the accuracy of your location to three
2. DGPS. This feature will increase navigation
coordinates over water.
3. Voice Guidance. For automotive use, this
is an important safety feature for navigation.
4. Multi-channel design. The new parallel multi-channel
standard in GPS receivers are more reliable when maintaining
multiple signals to pinpoint a location versus using
5. Compass. Location data should display the
differences between True North (North Pole) and Magnetic
North (varies with terrestrial shifts) for better accuracy.
6. Map views. From street maps to topographical
maps, choose a GPS receiver that displays information
relative to its primary use.