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Car GPS Navigation Systems A Buyers Guide
In 1973 the U.S. Department of
Defence launched the Navstar GPS network. This consisted of 24 satellites
orbiting the earth every 12 hours and five ground stations. This positioning
system was made available for public use. With this capability, consumer
location devices were produced to accurately determine location and other data
such as current and average speed, directional heading, and elevation. These
GPS devices need an unobstructed view of at least four satellites to provide a
reliable 3D fix.
The GPS receiver overlays this
location data onto map files stored on the unit, to give a current position on
the map as well previous track. The receiver constantly recalculates position,
giving real time position.
A typical GPS device contains:
- 12-channel receiver - the quality of the receiver
determines how long it takes the device to acquire a 3D fix.
- Antenna to capture satellite signals - positioned
to get a clear view of the sky.
- CPU to process the data and overlay on maps
- DVD Hard-drive - where maps on DVD's or available
online are uploaded and stored. Some cheaper units do not upload the maps,
but reference them off the DVD or CD.
- Display Screen - mostly color with handheld units
using black and white
- Voice Interface - more advanced units
How The
GPS Device Gets A Fix
The first time you start your GPS
device, its data store is blank so needs a to collect satellite information to
determine your position. This is known as a cold start. Some units only take 30
to 45 seconds to acquire a 3D fix during a cold start, while others can take
several minutes. Subsequent position updates only take 3 to 4 seconds. If you
go out of range from losing line of sight, such as passing behind a large
building or through a tunnel, a good receiver will instantly recover, whereas
weaker units will require more time to reacquire a 3D fix.
How Different GPS Navigation Units
Differ
Location of Antenna - A factory installed in-dash unit
antenna is integrated into the dashboard where it has an unobstructed view of
the sky. Many portable models have a suction-cup-mounting device to position
the device on the windshield. Add-on antennas are also available. Regardless of
the type of unit and antenna, the important thing is to keep the antenna visible
to the greatest area of sky possible. Choose a unit where this can be done AT
THE SAME TIME as being able to maintain a clear view of the screen.
Screens and Display - important to check how bright these
are, and if they are clearly visible from the mounted position in bright day
light. Onboard navigation systems are generally color screens, and portable
units are black and white to save power. Larger screens and integrate better
with other vehicle electronics.
Input Buttons - most enroute buttons are on the
display screen. Ensure these are easy to use when driving; that is they are big
enough and colored sufficently to see without causing a driving hazard.
Map Media - Earlier models were CD-based,
requiring multiple discs to cover the entire United States. Newer in-dash
systems are DVD-based; only 1-2 DVD's required for an entire country of maps.
Cost - In-dash systems are usually more
expensive than portable counterparts. Aftermarket in-dash models usually
require professional installation and can be just as expensive as the factory
models.
Upgrading - always check how easy it is to
upgrade the firmware and maps on your GPS unit. Some units detach a portion to
be connected to the computer via USB, whereas others are done using a DVD.
Those units which can be upgraded online, are much more convenient.
Added Features of GPS Units
Apart from giving you a current
position, a number of GPS navigation devices can give you:
- A track of where you have been - the number of
tracks and waypoints stored varies from unit to unit. You may also want to
save on part of a track for future use.
- A path from your current position to your
destination
- Maintain commonly used navigation paths for
reuse.
- Points of Interest - user sets the types of
points of interest, such as tourist, bank ATM, petrol stations,
historical, accommodation, restaurants etc.
- Real time traffic reporting to avoid traffic
delays. This can also include road works.
- Voice recognition to receive destination
instructions, and voice guidance to give driving instructions
- Weather updates
- Street name navigation - instead of just turn
left 200m it was say 'Turn left into Stanley St'
- Integrated Multimedia players - MP3 players,
image viewers, and audio books.
- Onboard or Portable GPS Navigation
The downside
of onboard GPS Navigation units are susceptible to theft; and you cannot take
them with you to use in other vehicles or when travelling abroad. Portable
units, such as the Garmin StreetPilot 2720, can be used in multiple cars; being
easily moved from car to car. Depending upon the power supply and portability,
portable and handheld units can be taken when travelling or used on cycles,
boats, private aircraft etc.
For more information on
Go-Reviews.com Car Electronics Section.
Nicola Carr - Nicola is a technology
strategist and publisher of Go-Reviews.com.
She provides product reviews and buying guides on a wide range of technology.
Nicola is also a feature writer for Electrosmart Digital Publishing and RichMediaMix
demonstrating how technology is integrating into business and media.
Article Source: http://EzineArticles.com/?expert=Nicola_Carr
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