By Bob Gatton
If you own a fairly new GPS navigation system, you might not want to read any further. You already know how great they can be in keeping you from getting lost, finding alternative routes when the traffic is backed up, and finding retail stores and restaurants. GPS receivers are one of those devices that once you own one, you can't imagine not always having one.
First, let's start with a little background. All navigation systems work on the same principles. There are 27 GPS (global positioning satellites – 24 active and 3 backups) in orbit. Each sends a radio signal with three types of information:
- The ID number of the satellite sending the signal
- A signal that tells the GPS receiver where each satellite should be
- The time
The GPS receiver, with the above information, can calculate how far it is from a satellite. When it gets signals from at least three satellites, using triangulation, it can calculate where it is on the surface of the Earth. The GPS receiver also has software for road maps. It combines knowing where its position with access to its database of maps to direct you to a destination. This, of course, is a very simplistic explanation.
If they all work basically the same, what features should you look for? A few things to consider include the following:
- The display. Is it easy to see? Is the text easy to read?
- Speed. How quickly does the GPS receiver lock on the satellites, my three year old model usually takes a couple of minutes, newer models are usually quicker. Some are almost instantaneous.
- Menu system. Is it intuitive? If possible, try it in the store before you buy.
- POIs (points of interest). Points of interest are gas stations, restaurants, shopping, tourist attractions, airports and more. How many does the system have? Some of the better systems let you search for specific points of interest. For instance, you could search for a restaurant close to you, then refine the search for a Chinese restaurant. A few even offer restaurant and hotel ratings.
- Communication with user. How does the unit communicate driving directions to you? Most display the directions on the screen and have a speaker telling you the information. My old receiver would tell me "Left turn ahead." Usually good, but in some situations, I would take the wrong left turn. Better, newer models will tell you not only the direction of the turn, but also the name of the street: "Turn right ahead on Maple Street."
- MP3 capability. Several new models can store and play MP3 files. I would not put too much value on this, but that is just me.
- Bluetooth capability. Models with this feature link with your cell phone. You can use the GPS receiver as a speaker phone in your car.
- Speech recognition. Several premium models let you speak your instructions to the GPS receiver.
- Traffic information. A few systems have an extra radio that receives real-time traffic information. This can direct you around traffic congestion before you are stuck.
- Database updates.New roads are constantly maps be available for your receiver and if there is a cost for the update.
The next article will be a review of Magellan's Maestro 4040. I'll give you a short preview: I like it.
Bob Gatton is a consultant and freelance writer who covers home technology and home theaters.
| 
