CNET GPS buying guide

Before we dive into the types of navigation systems and buying advice, it's always good to get a little background on the technology and have a basic understanding of how it works. Originally developed in 1973 by the U.S. Department of Defense for military purposes, the NAVSTAR GPS network consists of 30 satellites orbiting the earth every 12 hours, and five ground stations that monitor the satellites' position in space and operational status. To determine your location and other data accurately, such as current and average speed, directional heading, and elevation, GPS devices use a receiver to acquire signals from at least four of these satellites. This is known as a 3D fix and it's why GPS antennas require an unobstructed view of the sky to work correctly.

Armed with your precise latitude, longitude, and other location data, the GPS receiver can overlay this information onto map files stored on the unit, revealing your current position on the map as well as where you've been. Since the receiver is constantly recalculating your position relative to the satellite's position, the GPS unit can track your location in real time. A typical GPS device contains a 12-channel receiver and an antenna to capture satellite signals, and a CPU to process the data. The quality of the receiver and your geographic location will determine how long it takes the device to acquire a 3D fix. For example, it's harder for the receiver to lock onto and hold a signal if you're traveling through a dense forest or an urban area with tall buildings.

The first time you fire up your GPS, it collects certain satellite information to determine your whereabouts. Known as a cold start, the receiver is essentially blank and needs to know what time it is, where the satellites are in their orbital patterns, and where it is in relation to the satellites. Most systems take around one to two minutes to acquire a 3D fix during a cold start, while some can take a few minutes. Thereafter, it can take as little as 3 to 4 seconds to lock in since the unit already has your coordinates and a general location of the satellites. A good receiver will instantly recover from a complete signal loss when you drive through a tunnel, for instance, while weaker units will require more time to reacquire a 3D fix. In some cases, you'll have to stop the car to give the receiver a chance to lock on to the requisite signals.

How well a GPS unit will work in your car depends on the location of the antenna. If your vehicle has a factory installed in-dash unit, chances are the antenna is integrated into the dashboard in a place where it has an unobstructed view of the sky, which is ideal. Many portable models are designed to be positioned directly on the windshield via a suction cup mounting device, giving the antenna a wide sky view. There are also add-on antennas available for GPS units that allow you to keep the receiver close to the front seat for easy viewing without sacrificing signal quality.

In-car navigation isn't for everyone; the price alone will cause many people to forgo this technology in favor of the good old paper map. However, if you drive for a living, or like to visit different places on the spur of the moment, GPS can make the driving more enjoyable, leading you to major attractions or guiding you through quiet, scenic back roads. As a business tool, GPS can be a tremendous aid for field service or delivery personnel, or if you frequent different cities on business trips. As the technology advances and we start seeing more real-time traffic report capabilities, it will be easier to avoid the bumper-to-bumper grind.

Like any technology, GPS isn't foolproof. You still have to rely on a strong satellite signal to pinpoint your position on the planet, so if you're driving in a heavily wooded area or an urban jungle, you have to have a good idea of where you've been and where you're going, as you may no longer be tracking your actual location. It's important to remember that GPS is a navigation aid that will enhance your driving experience, not an automatic pilot. Still, if you're prone to wrong turns and are constantly getting lost, this technology is for you.

Nearly all vehicle GPS systems come with a warning stating that drivers should not enter information into the unit while operating the vehicle. Some models actually lock the on-screen keyboard and touch-screen capabilities while the vehicle is moving as a safety precaution. Unless the device has the capability to accept voice commands, searching and creating routes while in motion should be left to a passenger, even if it comes with a remote control. With voice-guided driving directions, the driver doesn't have to glance at the screen; instead, it's a matter of waiting for the voice prompts to get you moving in the right direction.

Other than helping you get from place to place, automotive GPS systems offer little else in the way of entertainment, although we're seeing more models integrate such features as MP3 players, image viewers, and audiobooks. Also, off-road drivers will find GPS useful for exploring unpaved terrain and creating their own rendezvous points and trails based on their latitude and longitude coordinates.

Once you've decided it's time for an in-car navigator, your next decision is which type of system is best for you--an in-dash unit or a portable add-on model? Each has benefits and drawbacks.

Types: Factory option | Professional install | Portable units | Handhelds, cell phones, and add-ons

Factory option

Many of today's new cars offer in-dash GPS as an option, and some offer it as standard equipment. The earliest models were CD-ROM based and required multiple discs to cover the entire United States. Nowadays, any in-dash system worth its salt is DVD-ROM based, so maps for the entire country will usually fit on a single disc, two at the most. In-dash systems are usually more expensive than their portable counterparts, but they usually feature larger screens and integrate better with other vehicle electronics.

BMW and Acura were among the first to offer GPS navigation systems in select vehicles nearly 10 years ago, and now this technology is available on hundreds of models worldwide. BMW continues to offer on-board navigation with voice recognition and voice guidance on most of their new vehicles, with prices ranging from $1,800 and higher. Several car manufacturers have taken it a step further by taking real-time traffic and weather satellite updates and overlaying them on navigation maps, flagging trouble spots and providing constant updates of road closures, accidents, and delays.

Professional install

Even if you don't order your new car with a GPS option, after market in-dash models are available, but they usually require professional installation and can be just as expensive as the factory models. The Eclipse AVN-6620 goes for about $1,200, but this is a multifeatured system that not only has a 7-inch touch screen, but it also plays DVD movies, audio CDs, and has an AM/FM tuner.

The beauty of an in-dash system is how it integrates with the rest of your car's interior. There are no wires or 12-volt power adapters to contend with; no beanbag, suction cup, or adhesive mounts cluttering up the dashboard. Installation is clean and professional looking. However, they are still susceptible to theft, regardless of how well they are installed, and you can't take them with you to use in other vehicles.

Portable units

Portable automotive GPS may not look as sharp as some of the pricier in-dash models, but they allow you to easily move them from car to car. High-end models such as the Garmin Nuvi 750 and the Magellan Maestro 4250 provide nationwide coverage (and sometimes more) with maps stored on a hard drive, offer an easy-to-use interface, and are ready to use right out of the box with no need to download or unlock maps. Both models feature bright, colorful touch-screen displays and are easy to install and remove using a suction cup mounting mechanism. Plus, they provide text-to-speech voice-guided driving directions.

There are smaller and less-expensive models, such as the Garmin Nuvi 200 and, Magellan RoadMate 1200 that are icon driven and very easy to use. To find a destination, simply touch an onscreen button (for example, "Where to?"), select an icon, such as fuel, lodging, restaurants, or another point of interest category, and press Go to receive directions.

These systems are generally half the price of their more advanced, feature-rich siblings, but there are trade-offs. For example, the screen size may be smaller and you'll lose some of the more advanced features like integrated Bluetooth for hands-free calling or text-to-speech functionality. Still, these systems are an affordable way to bring accurate GPS navigation with voice-prompted driving directions to any number of vehicles.

Handhelds, cell phones, and add-ons

If you don't want to spring for a dedicated GPS system for your car, there are other options. The Garmin Nuvi series started a trend toward pocket-sized navigation devices. The entire series offers many of the features that you'll find in most of today's in-car navigators, including voice prompted turn-by-turn directions, detailed street maps, and an extensive points of interest database. However, they can also be used as a pedestrian navigator and is particularly helpful when visiting new towns or cities. They have built-in MP3 players with audio book support, a JPEG viewer, currency and measurement converters, and a calculator. You can even download European maps and a language guide if you'll be traveling abroad.

Another alternative that will be more useful in everyday life is a PDA with an integrated GPS receiver. Models, such as the Pharos Traveler GPS 525 and HP iPaq rx5900 Travel Companion, come with built-in antennas and mapping software, and also feature productivity and connectivity tools, so you can stay on track in your life and on the road. If you already happen to have a PDA, you can turn it into a powerful handheld GPS system using one of the many add-on adapters available, such as the Belkin Bluetooth GPS compact receiver, which utilizes Bluetooth technology to connect your PDA and GPS receiver without the need for wires. It comes with mapping software, a vehicle mounting cradle for your PDA, 12-volt adapters, and of course a 12-channel GPS receiver.

Finally, there's been an increasing trend to integrate GPS receivers into cell phones and smartphones. Some recent examples include the Samsung BlackJack II, RIM BlackBerry Pearl 8130, and Nokia N95. With the addition of a location-based service or mapping software, you can get similar features of an in-car GPS, including voice-guided directions and points of interest, right on your phone. While the functionality is great, a handset's smaller screen size makes it less than ideal for in-car use. Still, if you're in a pinch, a GPS-equipped smartphone or cell phone could come in quite handy.

Types: Display | Maps | Form factor | Navigation feature | Accessories

Display

Select a GPS model with a good color screen that can be read in all lighting conditions. The larger the screen, the more expensive the unit will be, but even big screens can be difficult to read in direct sunlight. Also, check the viewing performance of the display to make sure you can read it from any angle.

Maps

Look for a model that includes street-level maps. Some manufacturers charge extra to unlock maps from their Web sites or CDs, while others include only partial regions. This can get expensive if you're planning a cross-country trip. Make sure you can update the unit's firmware and mapping data. On most portable models, a USB or serial port lets you connect the system to a PC, where you can upload the latest maps and system software as it becomes available. On in-dash models, maps are typically read from an integrated DVD or CD player and only require the latest discs to be brought up to date.

Form factor

Choose a GPS unit to fit your traveling habits. If you do a lot of long distance driving, consider a model with a dedicated hard drive that stores maps of the entire country. Otherwise, a model that uses an SD card to store maps is a good bet, and you can buy additional cards to load more maps when necessary.


If you want to share one unit between many vehicles, look for a model that is lightweight and is easy to install and remove from your vehicle. Stay away from permanent mounting devices unless you plan to use the unit in just one vehicle.

If you decide on an in-dash model, pay the extra money to have it professionally installed. Unlike car stereo systems, which can be fairly easy to install, a GPS system requires careful placement of the antenna, and some systems require a special cable hookup to your vehicle's speedometer mechanism.

Navigation features

Like anything else, the more bells and whistles included in your GPS system, the more you'll end up paying, but there are certain features that are more or less standard equipment these days. Street-level maps with voice- and text-prompted driving directions are the foundation of any in-car GPS system worth it's salt, and we're starting to see systems that use text-to-speech technology to deliver specific street names rather than more generic instructions, such as "Turn right in 0.5 miles." A comprehensive POI database containing airports, hospitals, dining, shopping, service stations and more, is a must if you're traveling in unfamiliar territory, as is automatic routing from a POI, an address book, or your present location. Look for a device with touch screen controls, automatic rerouting when you veer off course, and variable map views, such as 3-D and bird's eye views. As you get into the high-end models, look for big daylight readable screens and real-time traffic and weather alerts, which usually require an annual subscription fee.

Accessories

Most in-car navigation systems are ready to use right out of the box and come with everything you need to get up and running in a matter of minutes. Still, there are accessories available that will help you get the most out of your investment, including auxiliary antennas that can be mounted at the base of your windshield to improve signal reception, and carry cases to protect your GPS unit when not in use. You can also pick up various mounting devices, including motorcycle mounting kits and low profile external antenna mounts that adhere to the trunk of your car. You can also purchase additional maps on CD media or flash memory cards, as well as AC adapters that let you use your GPS unit at home.

Virtually all vehicle GPS systems come with maps, although not all of them are detailed street-level maps. Most in-dash models use optical media, such as CD-ROM or DVD-ROM discs that come directly from the manufacturer with maps preloaded. In some cases, these discs are part of the package, but some vendors require that you purchase them separately or subscribe to a plan that provides updated discs on an annual basis. DVD media containing detailed maps of the entire United States are typically priced in the $300 range.

Top-of-the-line portable models provide comprehensive street-level maps on a hard drive, so you never have to worry about losing detailed coverage when you travel outside of a map region. This seamless coverage is what makes this type of GPS system so popular. Units that use removable media, such as flash memory cards, can hold as much detail as the memory card allows. For example, the Mio 136, a PDA/GPS device designed for use in a car and on foot, doesn't come with preloaded maps. Instead, it has 32MB of internal memory and comes with a 256MB SD (Secure Digital) card to hold detailed map regions. A typical map region, such as the Boston to Washington D.C. I-95 corridor, uses over 200MB of storage. If you want to cover more ground, you'll have to purchase extra SD cards and preload the necessary regions before hitting the highway. Changing SD cards on the fly is no big deal, but it can get expensive if you want nationwide coverage at your fingertips.

The least expensive units will come with base maps of the United States, which include major interstate roadways and highways. For some travelers, this is sufficient, especially if they simply want to track their progress on long-range trips. If the unit has enough memory or a slot that accepts flash media, you can add detailed maps as you go. It's rare to find an automotive GPS system that relies on internal memory to store maps since flash memory offers more flexibility.

Loading maps onto your GPS unit can be a time consuming process. First, you'll have to load the mapping software on a PC and connect the GPS device to your computer. Depending on the software, you can select pre-determined regions to upload, or you may have to pan the map and create your own regions, which requires constant adjustments to create a region that will fit on your memory card. In some cases, you have to visit the vendor's Web site to download maps to your PC, and then upload them to the GPS unit. Both methods may require an unlock code to access the maps, which usually carries an additional fee and can cost hundreds of dollars depending on the vendor.

The biggest advantage that in-car GPS devices have over paper maps is the ability to create electronic routes, complete with turn-by-turn directions, and in most cases, voice-guided directions. Depending on your GPS unit's feature set, it may be necessary to plot a route on your PC before heading out on the highway, although most, if not all, current models contain enough memory and map storage for on-the-fly routing. Creating a route involves entering a destination and letting the system determine a route from your current location.

Almost all the of the high-end vehicle navigations systems utilize touch-screen technology to make entering destinations and addresses as easy as possible, and a few select models let you access the on-screen keyboard via a wireless remote control. Some of the newer (and more expensive) in-dash models now feature voice-activated input, such as the 2006 Honda Civic Hybrid, where you train the system to accept spoken commands. This is a trend that is also starting to show up in portable units, such as the TomTom GO 930.

Routes can be calculated any number of ways, depending on your preference. You can ask for the fastest or the shortest route and you can tell the system to avoid certain roads, such as toll roads and interstate highways. This is particularly helpful if you know that a stretch of road is under construction, or is closed for some reason.

Once the system has your starting point and your destination, it calculates the best route according to your specifications and displays it on a map, highlighting each segment of road along the way. The map view is typically a 2-D view, although most of the latest systems are capable of displaying 3-D and aerial map views. You can also view the directions in text with details such as distance between turns and estimated time of arrival based on your current traveling speed.

Ideally, the system is capable of giving voice-guided directions, which lets the driver concentrate on driving without having to glance at the screen. With voice directions, it's almost impossible to get lost or miss a turn because you are alerted of your next maneuver well before you actually have to make it. The voice prompt typically warns you of your next turn immediately after you've completed a maneuver, then again as you're heading towards the turn (to give you enough time to safely change lanes), then one more time as you approach the actual turn or exit ramp. Newer systems like the Magellan Maestro 4040 and the Garmin StreetPilot c580 feature text-to-speech functionality, which actually tells you the name of upcoming streets. If you still manage to miss the turn or deviate from the original route, the system will calculate a new route based on your present location.

Of course, an in-car navigator is only as good as its receiver, and since not all GPS systems are created equal, some are more accurate than others are. The same goes for mapping data and directions; a good system will have up-to-date maps that can differentiate between one-way streets, dead-ends, and so on. As a rule of thumb, GPS systems that use NAVTEQ or TeleAtlas digital maps are among the most accurate as for mapping detail.