I like this article. It gives a great background to the main features of a GPS Navigation System used for cars. It goes over the basic stuff, but you get an idea of what to expect in a GPS Navigation System. You can also find out some of the many additional features that come with upgraded versions of these car navigation systems.
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.
Garmin StreetPilot 2720 Traffic-Ready Portable GPS Navigator
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.
[tags]gps car navigation system, gps device, gps receiver, garmin[/tags]
I’ve had it for about a month now and it’s taken me all over MA and NY. It has all the right features. The one thing I don’t like is the keyboard, but it’s worth the extra two seconds it takes to type something in. It’s worth paying a few dollars more for the text to speech and it’s thinner than the tomtom OneXL which is in the same price range. (The OneXL doesn’t do text to speech either.)
The voice is plenty loud, the map is easy to read, and I think it’s nice that the power connector is on the back, it looks better than having one on the side.
A+++ Garmin did a good job with this.