Features

If you are thinking about buying a GPS receiver, it is helpful to know all of the features that GPS receivers offer today. That way you can pick the receiver that is perfect for you. The chart below highlights the most important features available today:

Essential

Feature Option Description

Receiver Multiplex Multiplex receivers have only one channel. They pick up one satellite signal at a time, cycling through a few satellites. They work much better in open environments, as their connection can easily be disrupted by buildings or other obstacles. The most affordable models use multiplex receivers.

Parallel-channel Parallel-channel receivers have several channels, and lock onto many satellites at the same time. They don't lose satellite connections very easily and they can pinpoint the location more exactly. These receivers were once fairly expensive, but there are several affordable models now on the market. If you plan to use your receiver in a big city or mountainous area, you should probably get one with parallel channels.

Antenna Quadrifilar Quadrifilar antennas are a length of coiled wire in a plastic housing that protrudes from the receiver. You may want to look for a model with a removable quadrifilar antenna, so you can place the antenna on your dashboard for a better "view" of the satellites. Quadrifilar antennas are best at receiving transmissions from satellites near the horizon, and not so adept at receiving signals from satellites overhead.

Patch Patch antennas are flat, and they are usually built in to the receiver. They have the reverse strengths and weaknesses of a quadrifilar antenna: They are better at detecting satellites that are directly overhead and not as good at detecting satellites near the horizon.

Power Battery Hand-held receivers will use batteries as a power source. This means portability. Be sure to find out what kind of batteries a hand-held unit uses, and how long they typically last.

External Source Some handheld receivers can accept external power, which is handy if you plan to be driving all day with your GPS on and don't want to drain the batteries. Car, boat or airplane in-dash GPS receivers will run on an external power source provided by the larger unit it's hooked up to. These devices are not mobile.

Display LCD Panel All GPS receivers display information on an LCD panel.

Color LCD Panel These displays make it easier to read maps on the receiver and help you distinguish between different routes you have created in the same area. Color panels often use more power than B&W panels, so they drain batteries faster.

Map Datum WGS 84 WGS 84 is the default map datum for any GPS receiver. It is a system developed around the emergence of GPS technology and is standardized for universal use.

Additional Eventually maps of the whole world will be converted to WGS84, a GPS standard datum. In the meantime, check to see that the GPS receiver recognizes the map datums used in your area, or areas you plan to travel to.

If you are thinking about buying a GPS receiver, it is helpful to know all of the features that GPS receivers offer today. That way you can pick the receiver that is perfect for you. The chart below highlights the most important features available today:
Essential
Feature	Option	Description
Receiver	Multiplex	Multiplex receivers have only one channel. They pick up one satellite signal at a time, cycling through a few satellites. They work much better in open environments, as their connection can easily be disrupted by buildings or other obstacles. The most affordable models use multiplex receivers.
Parallel-channel	Parallel-channel receivers have several channels, and lock onto many satellites at the same time. They don't lose satellite connections very easily and they can pinpoint the location more exactly. These receivers were once fairly expensive, but there are several affordable models now on the market. If you plan to use your receiver in a big city or mountainous area, you should probably get one with parallel channels.
Antenna	Quadrifilar	Quadrifilar antennas are a length of coiled wire in a plastic housing that protrudes from the receiver. You may want to look for a model with a removable quadrifilar antenna, so you can place the antenna on your dashboard for a better "view" of the satellites. Quadrifilar antennas are best at receiving transmissions from satellites near the horizon, and not so adept at receiving signals from satellites overhead.
Patch	Patch antennas are flat, and they are usually built in to the receiver. They have the reverse strengths and weaknesses of a quadrifilar antenna: They are better at detecting satellites that are directly overhead and not as good at detecting satellites near the horizon.
Power	Battery	Hand-held receivers will use batteries as a power source. This means portability. Be sure to find out what kind of batteries a hand-held unit uses, and how long they typically last.
External Source	Some handheld receivers can accept external power, which is handy if you plan to be driving all day with your GPS on and don't want to drain the batteries. Car, boat or airplane in-dash GPS receivers will run on an external power source provided by the larger unit it's hooked up to. These devices are not mobile.
Display	LCD Panel	All GPS receivers display information on an LCD panel.
Color LCD Panel	These displays make it easier to read maps on the receiver and help you distinguish between different routes you have created in the same area. Color panels often use more power than B&W panels, so they drain batteries faster.
Map Datum	WGS 84	WGS 84 is the default map datum for any GPS receiver. It is a system developed around the emergence of GPS technology and is standardized for universal use.
Additional	Eventually maps of the whole world will be converted to WGS84, a GPS standard datum. In the meantime, check to see that the GPS receiver recognizes the map datums used in your area, or areas you plan to travel to.

Standard

Feature Description

Internal Maps All receivers will give you your latitude, longitude and altitude, but they don't all show you your location on a detailed map. When you're shopping for a receiver, decide what kind of map you'll need and make sure the receiver you purchase offers that type of map. Many receivers contain a general map for the world in memory, but this map may only show you major roads and bodies of water. Some receivers have a wide array of other maps stored in memory or can download detail maps.

Map Cartridges Some receivers accept special map cartridges with more detailed maps of specific areas.

Download Maps Some of the newer GPS receivers have download capability that allows you to download maps stored in your computer into your receiver.

Way Point Capability With this feature, you can record certain way points -- locations along your path or on a map -- and arrange them in a route. Your receiver will then guide you from way point to way point along your route. This route mapping is handy because you can record the way you got somewhere so you can easily backtrack. You can also plan routes on detailed maps before you leave for a trip, and record all the information you need on your hand-held receiver.

Track Logging Receivers with a track logging feature can record your path as you move. This is useful if you want to backtrack or document your exact route for future use. It's also helpful to view your progress this way while you are traveling.

Storage Memory If you plan to use route-mapping and track logging extensively, you'll want to find a receiver that has enough memory. Consider how many way points you would want to store and find out what a receiver's maximum storage capability is. Also, look for a receiver with a backup system that will hold onto your information while you change the receiver's batteries.

Data Port One way to place yourself on a detailed map is to hook the receiver up to a computer (desktop, laptop or PDA). A data port provides such a connection so that you can use GPS data in conjunction with a number of software applications. Receivers with computer connection capability may also be able to download information to the computer. This is a good feature if you want to keep a collection of route maps (favorite hiking paths, tricky driving directions, good fishing spots). A receiver has limited memory, but you can store an entire catalog of route maps on your computer.

Sunrise/Sunset Times Some receivers can give you the times for sunrise and sunset at any particular location. This helps you plan your trip so you don't have to travel in the dark, which can be very useful to hikers, sailors, and pilots alike.

Odometer In most modern receivers, you can track how far you have traveled. Just like the odometer in your car, this feature can be useful in any number of ways.

Speedometer Most GPS receivers these days can track how fast you are moving. This is extremely helpful for estimating how long it will take you to get to your destination. Most receivers with speedometers will also give you an ETA.

Measurement Units Make sure a receiver can display the measurement units you will be using. If you will use the receiver in sailing navigation, for example, you will probably want a receiver that can give you measurements in nautical miles. Another feature to look for is the ability to display multiple measurement systems at a time, so that you could have elevation in feet, say, and geographical distance in kilometers.

Accuracy Warning Most receivers have some sort of system that tells you when something may be causing inaccurate positioning. This could either be due to poor satellite reception or to a receiver malfunction. In a lot of GPS applications, accurate positioning is critical, so be sure to find a receiver that will tell you when there is an accuracy problem.

Standard
Feature	Description
Internal Maps	All receivers will give you your latitude, longitude and altitude, but they don't all show you your location on a detailed map. When you're shopping for a receiver, decide what kind of map you'll need and make sure the receiver you purchase offers that type of map. Many receivers contain a general map for the world in memory, but this map may only show you major roads and bodies of water. Some receivers have a wide array of other maps stored in memory or can download detail maps.
Map Cartridges	Some receivers accept special map cartridges with more detailed maps of specific areas.
Download Maps	Some of the newer GPS receivers have download capability that allows you to download maps stored in your computer into your receiver.
Way Point Capability	With this feature, you can record certain way points -- locations along your path or on a map -- and arrange them in a route. Your receiver will then guide you from way point to way point along your route. This route mapping is handy because you can record the way you got somewhere so you can easily backtrack. You can also plan routes on detailed maps before you leave for a trip, and record all the information you need on your hand-held receiver.
Track Logging	Receivers with a track logging feature can record your path as you move. This is useful if you want to backtrack or document your exact route for future use. It's also helpful to view your progress this way while you are traveling.
Storage Memory	If you plan to use route-mapping and track logging extensively, you'll want to find a receiver that has enough memory. Consider how many way points you would want to store and find out what a receiver's maximum storage capability is. Also, look for a receiver with a backup system that will hold onto your information while you change the receiver's batteries.
Data Port	One way to place yourself on a detailed map is to hook the receiver up to a computer (desktop, laptop or PDA). A data port provides such a connection so that you can use GPS data in conjunction with a number of software applications. Receivers with computer connection capability may also be able to download information to the computer. This is a good feature if you want to keep a collection of route maps (favorite hiking paths, tricky driving directions, good fishing spots). A receiver has limited memory, but you can store an entire catalog of route maps on your computer.
Sunrise/Sunset Times	Some receivers can give you the times for sunrise and sunset at any particular location. This helps you plan your trip so you don't have to travel in the dark, which can be very useful to hikers, sailors, and pilots alike.
Odometer	In most modern receivers, you can track how far you have traveled. Just like the odometer in your car, this feature can be useful in any number of ways.
Speedometer	Most GPS receivers these days can track how fast you are moving. This is extremely helpful for estimating how long it will take you to get to your destination. Most receivers with speedometers will also give you an ETA.
Measurement Units	Make sure a receiver can display the measurement units you will be using. If you will use the receiver in sailing navigation, for example, you will probably want a receiver that can give you measurements in nautical miles. Another feature to look for is the ability to display multiple measurement systems at a time, so that you could have elevation in feet, say, and geographical distance in kilometers.
Accuracy Warning	Most receivers have some sort of system that tells you when something may be causing inaccurate positioning. This could either be due to poor satellite reception or to a receiver malfunction. In a lot of GPS applications, accurate positioning is critical, so be sure to find a receiver that will tell you when there is an accuracy problem.

Extras
Feature	Description
Differential GPS	Differential GPS is a technique that utilizes a second GPS receiver at a known location to correct for satellite signal inaccuracies. If a receiver already knows its exact location, it can check the accuracy of the signals it is receiving. This second, stationary receiver then broadcasts any accuracy adjustments to your receiver.
Built-in Database	GPS receivers designed specifically for airplanes or boats may have way points, or landmarks, already programmed into them. These might include airports and ports.
Rotatable Screen	Some GPS receivers have a display that rotates from a vertical position to a horizontal position. This feature might be useful if you plan to mount your receiver horizontally in your car some of the time and carry it vertically in front of you at other times.
User-changeable Fields	Receivers with this feature give you some extra control over how you look at information. Basically, you can customize different fields so they show you only the information you need for a particular activity.
Waterproofing	If you will be using GPS on a boat or while hiking, you should look for a receiver with good waterproofing. Some receivers are sealed so that they are completely waterproof while others are merely constructed so they resist water. Consider the conditions in which you will be using your receiver, and look for an adequate amount of weatherproofing.

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