How to choose a GPS Navigation Unit

Most GPS receivers use the same GPS receiver/processing chip, and most use either of the two main suppliers of map data. So, in theory, with so much the same, you'd think there'd be little to choose between different units.

If you think this, you'd be very wrong. There are great differences in terms of how the data is presented, and how you use the unit to program in destinations, waypoints, and other information.

Bad units have a distressingly complicated and non-intuitive interface that is difficult to understand, and waste much of their screen display on showing useless information. Good units offer a much easier to understand interface, and present helpful information clearly on the screen for you to conveniently and safely quickly glance at and understand while driving.

The number of different brands and models of GPS units is rapidly expanding at present. Prices are dropping, new capabilities are being offered, and smaller units are now rivaling their larger predecessors, offering the same advanced features in more convenient sizes.

GPS units are designed for several quite different types of end use. Two applications that we will not consider at all here are for aeronautical and marine usage, but if you're considering purchasing such a device, the chances are you'll still find most of our information helpful and relevant.

We're primarily focusing on portable devices you can use in an automobile, with a vague secondary focus on portable devices for outdoors hiking.

Feature	What it means and what to look for
Model	Make sure you're accurately comparing the same model with the same model when checking prices.
Price	Understand what it includes - sometimes the price is the price of a 'bundle' or kit complete with extra components, sometimes the price is for the unit alone.
Review Date/Details	If using review information to help your decision, keep in mind that units often have software upgrades over their life, and these upgrades can sometimes improve shortcomings and add new features.
Warranty	The longer the better!
Support	Toll free support and preferably for extended hours.
Inclusions	Ideally you want the unit, documentation, a mounting adapter, mains power supply and a car power adapter, mapping software and map data, a suitably sized removable data card (commonly SD), and a data connector between the unit and your computer (usually USB). A carry case is also helpful.
Runs out of the box	Some units are ready to go almost instantly, others require you to first copy data from a DVD to some type of media card (eg an SD card) and possibly to register software, etc. Clearly units that are ready to go right out of the box are preferable.
Size	The smaller, the better, although screen size (the bigger, the better) is a limiting factor.
Weight	The lighter, the better. Consider however the total weight of what you'd travel with - the unit itself, plus the mount car power charger, and any other necessary accessories.
Mounting Accessories	Ideally, you want to be able to mount the unit either on the windshield or on the dash of the car, with some type of removable/reusable mount so you can move it easily from car to car.
Screen Size	The bigger, the better, but note, below, that the pixel count is as important as the screen size. An okay screen size is 3.5" diagonal, a good screen size is 4" or more, but when screens start to get to 6" or larger, you start to have compromises in terms of where it can be conveniently located in your car, and of course, the unit becomes bigger, heavier, and more difficult to travel with. We consider screens smaller than 3.5" to be unacceptably small.
Screen Pixels	The more, the merrier. Screen pixels are at least as important than screen size - more pixels on a slightly smaller screen can sometimes be more readable than fewer pixels on a slightly larger screen. An okay screen resolution is 240 x 320 pixels, a good screen resolution is 272 x 480 (or more) pixels. The more pixels per inch, the clearer and crisper the resolution. To give you a comparative measure, computer screens are usually in the order of 70 - 90 pixels/inch.
Screen Colors	The more, the merrier. Most mapping software seems to only have a very limited number of colors (16 or so) but more colors beyond that for the extra information the GPS unit adds to the map helps you to instantly see and recognize what is being displayed on the screen. Avoid units that only display data in black, white and shades of grey.
Screen Visibility	Important that it can be clearly read even when the sun is shining directly on it.
Screen Backlighting	You want multiple levels of backlighting so as to adjust for optimum comfort when driving at night.
Day/Night Mode	Some units will automatically switch between day and night colors and brightness so as to make the map display most visible in low and full light conditions. They can do this because they know, based on where they are and the time of day/time of year when the sun rises and sets. Others allow you to manually switch between these modes, others have no option at all.
Controls	Does the unit use a touch screen or buttons (or both)? Because you may be driving and also attempting to adjust your GPS, you want big buttons or touch screen areas that are easy to quickly touch/push rather than small fiddly controls that are too distracting.
Interactive help files available	It is very helpful to be able to get an immediate explanation of what options mean while actually on the page in the unit.
Limited functionality when moving	Some units have the option to limit the things you can do with it while in motion, and some units have a hardwired refusal to allow you to do many things while moving - allegedly for your safety, but more commonly at great inconvenience to you, and to anyone else in the car who might be designated as the navigator. This is a feature you probably don't want.
Graphics processor speed	How quickly does it refresh the map image while you're driving? You want one that responsively refreshes as you are moving and turning, rather than one which very slowly updates.
GPS Receiver	Most receivers use the SIRF brand of chips, which seems to currently be the 'gold standard' in terms of sensitivity and performance.
Max number of satellites simultaneously tracked	Although some units are promising an ability to track as many as 16 satellites simultaneously, it is very rare to have more than 12 visible in the sky simultaneously, and even if more were visible, the extra precision from extra satellites is negligible. There's no real benefit to being able to track more than 12 satellites at once.
WAAS enhanced	This significantly improves the accuracy of the unit.
Dead reckoning capability	This can be very helpful in areas with poor signal, such as downtown surrounded by high-rise buildings.
Satellite display	Does it show how many satellites it is receiving data from (ideally in a diagrammatic representation of the sky)? This helps you understand how good the location data calculation may be, and also shows you where your antenna is most sensitive and where it is blocked.
Accuracy calculation	Does the unit show its calculated estimate as to the accuracy of the data it is displaying?
Can the unit show you your current latitude and longitude and compass heading	This can occasionally be useful, especially if you're going off-road.
Can the unit show you your current altitude	Of little practical value, but it can be very interesting to see your varying height as you travel through the mountains.
Can the unit show you the exact time	Because GPS units can synchronize their clocks to the incredibly accurate time clocks on the satellites, there is no more accurate source of time available to you.
External antenna capability	Modern SIRF units seem to perform amazingly well without an external antenna. Earlier units definitely need an external antenna. However, having the ability to add an external antenna if needed adds to the overall functionality of the unit.
CPU processor speed	This is most apparent when asking the unit to calculate or recalculate a route. It should be able to do this for a 100+ mile route within about 15 seconds.
Trip Computer functions	Does the unit offer 'trip computer' functions such as average, current, and maximum speed, distance traveled, time spent driving (and time spent stopped)?
Battery Type	Even if you're planning on mainly using your unit in the car, there may be times when you can't use the car's cigarette lighter power supply. Does the unit use rechargeable batteries or regular batteries? How many does it use? If they are rechargeable, are they standard sized batteries you can buy anywhere, or are they unique to this unit (ie harder and more expensive to replace)? If they are rechargeable, can they be replaced by the user or does battery replacement require returning the unit back to the factory?
Battery Life	How long does a set of batteries last with medium backlighting? If the batteries aren't rechargeable, you can divide the cost of a new set of batteries by their expected life to get a cost per hour of operation.
Power Input	Ideally the unit should accept external power via a USB port, making it compatible with a wide range of chargers and also allowing it to be recharged from your laptop or regular computer.
Auto Power On/Off	Some units, when connected to, for example, a car's power supply, will switch on and/or off when the car power goes on and off. Some units will automatically switch off if there's been no movement for an extended period of time.
Mapping
Map provider	The two main sources are Navteq (possibly slightly superior) and Tele Atlas.
Countries provided	The more, the better. Ideally both the US and Canada as a minimum.
Update policy, frequency and cost	Annual updates are desirable, but beware of cumbersome upgrade methods with copy-protection that require you to validate with your original disk, and beware of updates that cost ridiculous amounts of money (sometimes as much as $200).
Other countries also available	It is relatively common to find some European countries also with mapping data available, and sometimes Australia (and perhaps New Zealand) too.
How is map data loaded into the GPS receiver	SD cards seem to be the lowest cost and most convenient format for data to be loaded into the receiver. Other media also exist, but may not have as much capacity or be higher priced.
Can the entire US be loaded into the unit	The best units will be able to have all the US and Canada loaded in the unit at the same time. This gives you the most convenience - no matter where you go, you have the mapping data available already in the unit.
Speaks Directions	A voice that speaks directions is very helpful, because it means you can keep your eyes on the road and don't need to look at the GPS receiver to know when and where to turn.
Speaks Street Names	If the unit can pronounce street names, this is even more helpful - it is the difference between a generic type instruction such as 'take the next road on the right' and a more specific instruction 'take the next right on Smith Street'.
Languages spoken	Some units give you a choice of American or English accents, and a choice of male or female voices, as well as a variety of different languages.
2D/3D	Some units offer a so-called 3D view of the map - this is a sort of a bird's eye view looking down from behind your location on the map, looking forward to where you are and the roads ahead, with an exaggerated perspective. It looks nice for a while, but most people will find the classic 2D 'map style' view is more helpful.
Can you choose between North up or Direction of Travel up	Typically most people will want the unit to be oriented so the screen points up in the same direction as you are traveling. That way, left turns in real life appear as left turns on the map, etc. Sometimes though it is helpful to have a 'north up' orientation, like on a traditional map. This is particularly helpful when zoomed out a long way or when planning a route - when north is up, you're seeing a map same as you're used to with a regular printed map.
Split screen mode	Units with larger screens sometimes allow you to split the screen into two separate screens, each with different information on it. For example, I have one of my units split so one screen is a highly zoomed in detail of the nearby area, with direction of travel up, and the other screen is a zoomed out overview of the district area, with north up.
Map scale shown	What use is a map if it doesn't show you the scale, allowing you to understand 'this many inches on the map equals so many miles on the road'? It would be useless, right? Similarly, you need a scale on your GPS map display so you understand the meaning of distance there, too. This is even more essential with GPS units that automatically zoom the scale in and out without telling you.
Number of POIs provided	Units can offer prodigious numbers of Points of Interest (POIs), with some units offering as many as 5 million, 10 million, or even more POIs.
Number of user POIs that can be added	It is amazing how quickly you start adding extra Points of Interest yourself. You definitely want to have the ability to add as many extra POIs (and destinations) as possible.
POI information includes phone number	This is very helpful, for example, you can phone a restaurant to check their opening hours or to make a reservation.
POI proximity alert	This has an obvious benefit, and a more subtle one too. The more subtle benefit is that if you're in a place with traffic cameras, you can program their locations into your unit and have it caution you any time you're approaching a traffic camera.
Speed limit warner	This is of little value unless the unit also 'knows' the speed limit on the road you're traveling.
Does it show both miles and kilometers	If it shows both, you can conveniently switch between units when traveling to countries (eg Canada, Europe) where km are used.
Route Planning
How to enter addresses and other data	Main choices are QWERTY keyboard layout, ABCD table layout, or choosing each letter, one at a time, with a scroll wheel.
Can you build a multi-stop journey with waypoints	This can be helpful if, eg, you are planning an itinerary such as 'first I want to go to the supermarket, then to the mall, then to the bank, then to the car dealer, then back home.
Will it solve the 'traveling salesman' puzzle	This allows you to enter a series of destinations and the unit computes the best order to visit all of them as quickly as possible. This is a rare feature offered only by a very few units.
Can you program assumed speeds for different road types, and if so, how many different road types?	This information helps the unit make the best choices for routing you the quickest way, and will also help it more accurately predict your time of arrival at your destination.
Can you program preferences for road/route types	Some units allow you to specify preferences for things like 'avoid/prefer freeways' and similarly for ferries and various other route options.
Can you choose different settings for different types of vehicles	Some units allow you to choose between cars, trucks, bicycles, and possibly other types of transportation, with different settings (eg for typical speeds on different road types) and preferences for each.
Does the unit present you with multiple route choices to choose from	Some units show you different routes on the screen for you to choose between, allowing you to visually see the different choices. This can be helpful if you have some familiarity with the route, allowing you to do a reality check on the route(s) being proposed.
Can you choose between fastest/quickest and shortest route options	Units will often give you this choice - for example one route might be longer, but because it uses the freeway, might be faster to travel than an alternate route which is shorter but on surface streets. Use this option carefully. I inadvertently set a unit to 'shortest' rather than the usual quickest choice, and instead of just putting me directly onto a toll road and having me drive 25 miles nonstop at 70 mph, it took me on surface streets all the way, usually in 30 mph speed zones and with stop lights on every block, so as to save me a couple of miles of distance, but at a huge cost of extra driving time.
Will it show breadcrumb trails?	Some units can leave a row of dots on the map to show where you've been. This can be helpful in some situations (especially off roading).
Extra Features
Bluetooth Phone Integration	Some units can connect to a phone via Bluetooth. This can be helpful if, for example, you select a restaurant from the map and then want to dial its number.
Export data to laptop	Some units allow you to export the realtime GPS data to, eg, a laptop mapping/navigation program. This is helpful if you have a second person as your navigator and able to use a laptop while you're driving.
Can it play MP3 or other digital audio	Some units can do double duty as an MP3 player. This is of very little value to most people, however; it is much better to have a dedicated MP3 player for your music.
Can it play MP4 or other digital video	Some units can do double duty as a video player as well, typically playing videos that you've stored on the player's removable memory card. Unless you've got a large and clear crisp screen, and a huge sized memory card, this is unlikely to be of much use. Some units can also accept inputs from other players - for example from an Apple iPod. In this case, the unit can be more helpful because you're able to see longer videos, and hopefully on a larger screen than the iPod.
Can it display pictures	Some units allow you to store digital pictures, which you can then display on the unit's screen. This is another low value gimmick application for most people.
Integrated with real time traffic reporting	Some units can receive extra data through a radio receiver that gives you location specific instantaneous information on traffic jams, road construction, accidents, etc. Total Traffic Network/Clear Channel is one such provider of this information, XM Satellite Radio is another, MSN Direct is a third (and currently offers the most extensive range of location data).
Integrated with other location services	Some units offer additional data services such as local movie show times, local gas station prices, etc (using MSN Direct).

Although the table above might seem to imply that choosing a GPS receiver is very difficult and complicated, happily this is not the case. But do use this checklist to ensure you're getting what you expect and hope for, and to assist you to compare different units and understand the strengths and weaknesses are of each unit.

Chances are that no matter what unit you choose, you'll be delighted with the almost magic ability of the unit to always tell you exactly where you are and to usually (!) help you to get where you need to be.

See the links at the top right of the page to visit other articles in our GPS series.

You may freely reproduce or distribute this article for noncommercial purposes as long as you give credit to me as original writer.