All brands of GPS receivers use basically the same method to precisely locate your position. But they’re designed for many different activities such as hiking, driving, boating, or other outdoor sports. While there is some overlap, GPS receivers are categorized as Road, Marine, Outdoor and Portable, or Sport.

The electronics are often very similar, but the software, controls, and case can be very specific to their task.

Road GPS

GPS receivers designed for road use are typically intended for use in a car, although a few are specialized for motorcycle (or even bicycle) applications. They usually offer wider screens than an outdoor unit intended for hiking.

They also have a wide variety of additional features and applications. Points of Interest (POIs), sites you may want or need,
such as restaurants, hotels, hospitals and more are pre-loaded onto a vehicle GPS unit.

Marine GPS

Some GPS units are intended to function in both auto and marine environments. But those that are specifically designed for sailing, boating, fishing, and other water activities provide specific hardware and software features.

A marine GPS may come pre-loaded with street maps, but the focus of their software is on inland lakes, coastal features and similar features. They typically provide additional data on weather, water depth, channel contours, and other essential data for boaters.

The screens tend to be larger than other types, but more importantly the entire unit is built for tougher conditions. They will normally be waterproof, corrosion resistant, with greater impact resistance.

Outdoor GPS

Some of the features for a marine GPS are often found in outdoor Personal Navigation Devices (PND). PNDs are water-resistant usually protected from immersion up to a depth of 1 meter of water for 30 minutes. The cases are sturdy and can tolerate a wide range of temperature, atmospheric pressure, and other stresses. They will withstand all the typical conditions you might expect to find on the trail, especially in the mountains.

Outdoor or portable PNDs were among the first consumer electronics devices to use GPS technology. As a result of this, they often have a wider range of features than auto-oriented units.

The capacity to store dozens of topographical maps is necessary if you will be visiting several wilderness locations. Of equal importance is the ability to record hundreds of waypoints - points of reference along your intended and actual treks. It’s also especially helpful to have a 3-D view of important land features, such as mountains and valleys.

A compass can be helpful (although with the GPS unit, perhaps unnecessary). Also an altimeter, thermometer and other extras can be very convenient for GPS receivers used for hiking, mountain biking, geocaching, and other wilderness activities.

Sports GPS

An interesting variation on the outdoor and portable category is found in sports. Golfing is the most common example, where distance and angle to another point is critical to know. But many golf-oriented GPS receivers do more than simply displaying the distance to a hole. They will include features of the fairway and green, like surface curves, water  and sand traps, and more. The best ones can do that even when trees and other obstacles are present.

Summary

There is considerable overlap in the features of the various categories of GPS receivers and PNDs. Vehicle units can often be used on motorcycles, portables can be mounted on a mountain bike as well as function on a hike. Some marine GPS units can also be utilized in your auto or even on foot.

But to get the highest functionality with the widest array of features and the most specific value for your situation, it can be worthwhile to consider buying more than one Personal Navigation Device, one designed especially for your application. With prices dropping all the time, that’s easier today than ever.

The name is certainly odd and unique, but the Garmin Nüvi 855 GPS receiver is a user-friendly, practical device with outstanding features.

The 855 model offers speech recognition for voice commands as well as text-to-speech to guide you on your way. Tap the screen or speak a menu option and you’ll get 2-D directions to your destination and 3-D landmarks, if you wish.

Garmin nuvi 855 Portable Automotive GPS System w/ Lane Assist & Voice Recognition

Simply press a button on the remote that can be attached to your steering wheel to activate the speech recognition program. A simple spoken “Find Address” followed by the address you want to locate brings up the data you need. A brief and dependable ‘training’ is required for the unit to learn your voice, and the 855 improves with additional use.

Turn-by-turn directions will guide you easily through optimized routes. The Nuvi 855 announces the names of exits, streets, and additional features as you drive. If you ever lose your way - which is difficult with this unit - the Nuvi will get you back on track with the “Where Am I?” Command. It will give your exact latitude and longitude, along with the locations of the nearest hospital, police station, and closest address and intersection.

But even if you take a wrong exit or make a wrong turn, there is no need to worry. The Nüvi 855 can dynamically recalculate your route and get you back on route quickly. If you choose to operate the unit by hand, you’ll find the touchscreen easy to use.

That same screen is easy to read, also, for those occasions when you don’t want to rely on the audio to guide you. While it allows drivers to keep both hands on the wheel, there are times when you might want to get an overall view of your route. That’s easily accommodated thanks to the clear, 4.3″ color display that can be viewed from any angle and in full sunlight.

“Lane Assist” is one of the more innovative features of this model. The Nuvi notifies you of upcoming exits or turns by suggesting the best lane to be in. That gives you plenty of time to make the change safely. If you want additional detail, simply use the Junction View. The realistic view of the landscape provides road detail, signs and more just as you would see them on your trip.

As you travel you can enjoy any of nearly 6 million Points of Interest programmed into this excellent Garmin GPS receiver. Navteq provides the map data for a huge database of restaurants, hotels, gas stations, and even ATMs in the U.S., Canada, and Puerto Rico. And you can also add your own custom POIs.

As you are driving, you can enjoy your GPS receiver even more, thanks to a built-in MP3 player. You can play music or other audio stored on SD memory cards that fit right into the unit. The Nuvi mounts easily onto your window or dashboard, so you can have the songs right where you want them. And it’s so slim and lightweight (3.9″ x 3.1″ x 0.7″ - 6.1 oz) you can place it in your pocket when you leave your car.

Try the new Garmin Nuvi 855. You will see that GPS receivers now can do a lot more than just draw a map.

Garmin nuvi 855 Portable Automotive GPS System w/ Lane Assist & Voice Recognition

Stay ahead of the curve with the Garmin nüvi 855. This premium navigator features voice-activated navigation and lane assist with junction view. Now you can keep both hands on the wheel, tell nüvi where to go and maneuver complicated interchanges with ease.

If you buy a quality GPS receiver you can expect to get a whole range of useful accessories right in the box. Mounts and mounting hardware, USB cables, power adapters, and more are standard. But there is an array of add-on products that are much more than just eye candy to tempt techno-geeks. They actually make owning your personal navigation device a much richer experience.

You could start with something simple, but highly helpful, like Ikross LCD Screen Protectors. These clear, scratch resistant, semi-sticky pieces of plastic can help protect your touchscreen for months or more. If you have an auto unit, they can reduce the need to clean your screen often. Wipe the protector or just replace it after a while. Better still, when you use an outdoor unit, they can provide that extra layer of protection that will keep your screen looking good for years.

In that same arena, it’s always a good idea to have a good carrying case for your PND. Some models come with one that is as good or better than most accessories. Others will benefit from a high-end add-on. Of course, if you lose the one that came with the unit, they’re a must. Garmin makes several for its nuvi line. Be sure to get the right one for your model. They’re tough and many come with a belt loop or other attachment to make carrying easy.

Virtually all GPS receivers come with one or more mounts (and hardware). But cars, motorcycles, mountain bikes, and more all come in a huge variety of shapes and styles. Your mount may not be ideal for your circumstances. Also, many states have laws that restrict where and how you can mount your PND. Some, for example, forbid using the suction-cup mount that makes attachment to your car windshield a breeze.

Garmin makes a Portable Friction Beanbag Mount that works great. It’s a sand-filled little unit you just set on your dash. No screws required and it stays put. That also makes it easy to store or remove your GPS receiver to prevent theft when you’re out of the car. The Bracketron UFM-100-BL Nav-Mat Dash Pad is another, similar accessory. It’s weighted and has anti-skid material on the base so it will hold your GPS securely in place until you want to move it.

Software, maps and other data are another universal feature of all GPS receivers on the market today. They come pre-installed/pre-loaded and the vendors all offer updates on their websites. Even so, it can be worthwhile to investigate some of the add-ons offered by manufacturers and third-party vendors.

Marine GPS units benefit from a whole range of additional BlueChart g2 extras that provide detailed information about inland lakes, rivers, and the thousands of landmarks near waterways. East Coast, Gulf of Mexico, Alaska, Great Lakes…. The possibilities are endless. Garmin offers a complete range. If you can’t find what you’re looking for easily, you probably don’t want to go there!

Take a look around after you’ve used your GPS receiver for a short while. You’ll soon find there are a number of accessories that will significantly increase the value and pleasure of using your personal navigation device. Happy traveling!

GPS units taken on the trail several years ago provided direction and a simple map. Sometimes they included useful terrain features. Today’s GPS receivers have become true Personal Navigation Devices, and much more.

All but the most specialized units provide extensive maps, many with 3-D views of your immediate surroundings. The Magellan Roadmate 1470, the Garmin nüvi 855, the TomTom XL 340, and many others do this superlatively. But they also offer features that make your whole away-from-home experience better, like voice commands and text-to-speech directions, dynamic re-routing when you make a wrong turn, needed lane change or upcoming exit advance notice, and more.

The specialized SkyCaddie SG2.5 Golf GPS provides pre-loaded, detailed views of dozens of golf courses, and you can download many more. The Suunto X10 Military GPS watch provides an entire PND combined with an altimeter, barometer, thermometer and much more in a package that fits comfortably on your wrist. It makes an adventure trek infinitely easier.

Less specialized-application GPS units, like the Garmin GPSMap 478 or the Humminbird 383C Combo - designed for marine environments - provide an enormous range of features.

The 383C, for example, combines a GPS unit with sonar to make underwater surface features visible and fish finding easy. It also provides views and info on hundreds of nearby land features like marinas, coastlines, channel contours, and so forth.

The 478 can be used in either marine or auto situations with equal efficiency. It provides dozens of BlueChart g2 maps for marine use - coastal areas, inland lakes, and more - but comes with a City Navigator system that works as well on land as any other auto-oriented PND.

In the area of auto GPS units the globe is the limit. Apart from those mentioned above (the Magellan, the nuvi, and the TomTom) the Navigon 7200T is a stellar competitor. The Garmin Zumo 550 can also be used in your car, but really shines when you mount it on your motorcycle.

Get away from the water and the city into the wilderness and you’ll want to take along any one of dozens of outstanding outdoor GPS receivers.

The DeLorme Mapping PN-40 Earthmate makes a stellar companion in the mountains and along the trail. With its up-to-the minute-design dual processors and outstanding software you’ll never wait for directions. Long battery life and a high-resolution screen ensure that you’ll have no trouble reading the huge amount of data it can provide.

The Garmin Oregon 400T is a favorite among geocachers, outdoor types who love to hunt for planted treasure just for fun. The unit-to-unit data-sharing feature comes in really handy in that situation. In that hiking and climbing scenario, you also need a sturdy unit with every conceivable feature GPS designers have devised. The 400T delivers more than you’ll use in a year of daily use.

Your intended use for a GPS receiver might be in a car or on a motorcycle, mountain bike, boat, or just on a stroll along a mountain path or city street. Whichever, you’ll find a Personal Navigation Device that provides hundreds of easy-to-use features. With the addition of MP3, Bluetooth support, XM radio, and more, many of these units are well on the way to becoming indispensable all-round digital assistants.

GPS stands for Global Positioning System, and that name captures well what it does: indicate your position on the globe. How it does that is a fascinating tale that doesn’t require advanced mathematics to understand.

Before delving into the details of how that system operates, it’s helpful to have a basic knowledge of how positions on Earth are specified. The classic view provides one that’s easy to visualize.

Imagine a simple grid made of lines that wrap the globe ‘vertically’ originating at the Earth’s North Pole and fanning out then coming together at the South Pole. Then add a set of ‘horizontal’ lines that wrap the globe at right angles to the first set. That grid is the familiar longitude and latitude ‘mesh’ that is painted on every school room globe and map. Each line of lat and long are marked off in degrees that specify how far along one of them you are located.

Now, how is that ‘mesh’ used in connection with the GPS system?

The U.S. Air Force maintains a set of 24 operational GPS satellites (with 3 spares). Each satellite has the electronics and software needed to measure its own location, most importantly the distance from the Earth. It does that by sending a radio beam out and measuring the time needed to hit the Earth where the signal is picked up by ground stations.

Since distance = velocity * time, that measurement is pretty straightforward. Radio waves travel at the speed of light (~186,00 mph or ~300,000 kph) and the electronics measure the delay from when the beam is sent to when it’s picked up.

Satellites (and ground stations) can measure that delay accurately because they have clocks synchronized by atomic clocks that measure time to incredible accuracy. GPS Receivers don’t have atomic clocks inside, but perform some tricks to compensate.

Also because of variations in the atmosphere, the motion of the satellites, reflections off buildings, and other imperfections from this neat description, GPS systems have to correct for small errors in order to get the precision needed to locate your receiver to within a few meters.

Distance provides only one (albeit important) piece of the puzzle. Imagine you’re told you are 600 miles west of Kansas City. That puts you at the center of a circle of radius 600 miles, with KC somewhere on the circumference (the rim). But you don’t know exactly where. Now you’re told you are also 400 miles east of Denver. Another circle. Those two circles intersect at two points. A third intersecting circle will place you at exactly one unique point (to within measurement accuracy).

Since the GPS system is formed by satellites in space in cooperation with ground stations, it operates in three dimensions, not just the two provided by the surface of the Earth. So, the Global Positioning System uses spheres rather than circles. The calculations are more complex, but the idea is the same. Where the surfaces of four spheres intersect they determine a point, the point at which your GPS receiver is located.

Your GPS receiver is designed to ‘listen’ for the signals from four of those satellites, and uses the info provided to calculate your latitude and longitude. It overlays that unique point onto a map that resembles your surroundings, allowing you to navigate your way to anywhere you wish.