Glossary

  • 4 Level Gray: Reflective gray scale LCD screen. Color TFT screens work better in a variety of lighting conditions, and no current receivers use these displays.
  • AAA Tourbook: Street GPS units with this feature contain POI data from the Tourbooks published by the American Automobile Association.
  • Accuracy: Civilian GPS receivers are accurate to 10 meters (33 feet) and often achieve accuracy of 3 meters (10 feet). Accuracy varies depending on satellite geometry, number of satellites visible, atmospheric conditions, radio signal propagation, and other factors. Some GPS receivers display an accuracy figure in feet or meters. This is an estimated accuracy calculated by the internal software and varies between manufacturers. It should not be relied on or used to compare the accuracy of different receivers. But generally, a lower accuracy figure indicates more satellites in view and good satellite geometry.
  • Altimeter: GPS measurement of altitude is accurate to about 15 meters (49 feet) under ideal conditions. Units which have a barometric altimeter can improve on this accuracy, but the altimeter must be set to a known elevation or barometer setting.
  • Anti-Theft Features: On a street GPS, this feature typically allows you to set a password that must be entered in order to use the receiver. You may also be able to set a security location, which disables the unit if it is turned on at a different location.
  • App: A GPS navigation application used on a smartphone or a tablet.
  • Audio Book Player: This features enables you to play audio books through the GPS unit.
  • Auto Reroute: This feature, found on nearly all street GPS receivers, automatically recalculates the route if you take a wrong turn or deviate from the GPS-planned route.
  • Auto Orientation: On street and touch screen trail GPS receivers, automatically changes the screen display from landscape to portrait when you rotate the unit. Useful when you want to look ahead further along the route.
  • Auto Sort Multiple Destinations: This feature lets you plan the most efficient route to multiple destinations, which is useful for making deliveries or sales calls.
  • B/W LCD: Reflective black and white LCD screens which are now found only on wrist-top GPS receivers without mapping capability.
  • Basemap: All mapping trail GPS receivers and all street GPS receivers have basemaps. These maps are built into the unit and generally cover a larger area in less detail than the pre-loaded or loadable maps.
  • Batteries: Most trail receivers use common AA or AAA-size alkaline batteries. The unit should also be able to use NiMH rechargeable and lithium single-use batteries. Lithium batteries have the longest life under outdoor conditions, but NiMH batteries can be recharged hundreds of times. Get the newer NiMH batteries that retain their charge during storage. Street GPS receivers have internal rechargeable batteries.
  • Battery Life: Specified in hours with the unit running continuously. Long battery life is necessary in a trail GPS. Battery life can be extended to days by leaving the unit off except when checking your position and saving waypoints. Street GPS receivers are normally run from vehicle power and the battery is used only for pre-trip planning away from the vehicle.
  • Bluetooth(R): This feature lets you use your Bluetooth cell phone to make hands-free calls using the microphone and speaker on the street GPS receiver. In trail units, allows you share data with other units.
  • Color TFT: Backlit transreflective color LCD screen. These screens work well in bright sunlight and are backlit for use in poor light. 256-color screens are fine for maps, but if you want to look at photos on your GPS unit, you'll want 65K color.
  • Compass: While all trail GPS receivers have a compass page, the GPS cannot show your direction of travel while you are stopped unless it includes a magnetic compass. A 3-axis compass works when tilted.
  • COMPASS: A satellite positioning system operated by China that covers Asia and the Pacific and is planned to cover the entire Earth by 2020. Also known as BeiDou 2, it is not compatible with GPS.
  • Coordinates: Numbers and letters describing a physical location. Most trail GPS units can use many different coordinate systems. The most common are latitude and longitude and Universal Transverse Mercator. Most street GPS units display coordinates in latitude and longitude, although it's rare that you would use coordinates instead of POI's or street addresses.
  • Custom Maps: Lets you add non-proprietary maps. There are now many free sources of maps, and you can scan any paper map and load it as a custom map. For mapping GPS receivers, this is an essential feature.
  • Custom POI: Nearly every street GPS unit (and trail GPS receivers with street maps loaded) lets you save locations and POI's as favorites. This saves time next time you need to navigate to the same location.
  • Dashboards: Customizable screens with presets for specific activities.
  • Data Cards: Many GPS receivers use flash memory cards to increase the amount of memory in the unit. If you plan to add maps or store a lot of data in your receiver, make certain it uses SDHC or MicroSD cards.
  • Datum: The physical reference system used to make maps, based on surveyed points on the ground. GPS is based on the World Geodetic System of 1984 (WGS84), while most U.S. Geological Survey topographic maps are based on the North American Datum of 1927 (NAD27) Trail GPS receivers must be set to the correct datum when working with paper maps. If the wrong datum is used, GPS positions can be off by many feet or even miles.
  • DGPS: Differential GPS uses GPS receivers placed on accurately surveyed points to generate corrective signals and transmit them to DGPS-equipped GPS receivers. Commonly used for surveying, scientific, engineering, and navigation applications, DGPS can achieve accuracies of several millimeters.
  • Display Resolution: Expressed in pixels. More pixels means a higher resolution screen, allowing you to see finer map and photo details.
  • Emergency Location: This street GPS feature lets you quickly find the nearest emergency services, including police, fire, and medical.
  • Exit Services: Also called "Exit POI's", this feature shows you points of interest, including services, for upcoming freeway exits.
  • External Antenna Connector: If you plan to use your trail GPS extensively inside a vehicle, you may want to mount an external antenna on the roof of the vehicle for more reliable satellite reception.
  • Floats: Boaters may want a unit that floats, although for protection from the water, paddlers should enclose the GPS receiver in a waterproof bag. This also adds flotation to any unit.
  • FM Transmitter: Transmits audio from the GPS unit to your vehicle's FM radio receiver. This is especially useful for motorcyclists as they can hear the GPS prompts in their headphone-equipped helmets.
  • Fuel-Efficient Routing: When enabled, this street GPS feature chooses the route that will give you the best fuel economy.
  • Galileo: Under development by the European Union, the Galileo Positioning System will be fully compatible with GPS, increasing accuracy and reliability of existing GPS receivers. Galileo is expected to be fully operational in 2019. Garmin has a new trail GPS, the GPSMAP 66 series, that can use Galileo.
  • GLONASS: The Global Navigation Satellite System operated by the Russian Federation. GLONASS became fully operational in 2011. It is comparable in coverage and accuracy to GPS but requires a different receiver. Some of the newest trail GPS units have dual receiver systems and can use both GPS and GLONASS. Use of both systems increases signal reliability and accuracy
  • GNSS: Global Navigation Satellite System, the generic term for a complete satellite navigation system, such as GPS (NavStar), GLONASS, or Galileo. A GNSS includes the satellites, ground control stations, and user receivers
  • GPX: GPX is becoming the standard file format for transferring GPS data between receivers and computers.
  • High-Sensitivity Receiver: Nearly all street and trail GPS receivers now have multi-channel, high-sensitivity receivers. Each channel receives one satellite, so multi-channel receivers use more satellites simultaneously. Higher sensitivity means that the GPS unit can use satellite signals that are partially blocked by foliage. This means that your receiver will work better under difficult conditions- in forest, canyons, or among high-rise buildings.
  • Hunt/Fish Calendar: Hunters and anglers may find this trail GPS feature useful. It attempts to predict the best times for hunting and fishing.
  • Interface: USB is standard. The newer USB 2.0 standard is much faster than USB 1.1 and is useful if you plan to upload many maps to your receiver.
  • Internal Memory: The amount of internal memory determines how many maps, POI's, waypoints, routes, tracks, and geocaches you can store in the unit. This memory cannot be increased.
  • Junction View: On street GPS receivers, shows a picture of the exit signs at freeway off ramps.
  • Landmark Guidance: Calls out landmarks such as gas stations to help you find turns. Can be misleading because landmarks change far more frequently than street names. Don't buy a street GPS receiver with this feature unless it can be disabled.
  • Lane Guidance: This feature assists you in choosing the correct lane for an upcoming exit or turn.
  • Lifetime Map Updates: Free map updates for the life of the receiver. Otherwise, you'll have to buy and manually upload map updates. But also consider that map updates are huge files that require a large amount of free space on your computer and take hours to upload and install. If you don't want to bother then buy a unit without lifetime maps and just replace it when the maps get old. At today's low prices that makes sense for many users.
  • Lifetime Traffic: Free lifetime traffic services, usually in return for displaying ads on the screen.
  • Loadable Maps: Almost all mapping trail GPS receivers and street GPS units allow you to add maps yourself. If you plan to use the unit outside the coverage area supplied with the receiver, make certain you can add maps. Normally, the add-on maps must be bought from the GPS manufacturer.
  • Motorcycle Features: Street GPS receivers that are designed for motorcycle use are waterproof to the IPX7 standard, resistant to ultraviolet (UV) light, and have special touch screens designed for use with gloves. In addition, they usually have Bluetooth so cell phone calls can be made though the audio system in your helmet. POI's can be called by selecting them from the screen. Some units have optional XM satellite radio and weather.
  • MP3 Player: This feature lets you store and play music.
  • Paperless Geocaching: This feature allows you to save notes and clues with the geocache location in the GPS receiver so you don't have to carry printed notes.
  • Pedestrian Navigation: A street GPS feature designed to guide you around a city on foot.
  • Photo Navigation: This feature lets you navigate directly to a geotagged photo stored in the receiver. A geotagged photo contains the location where the image was taken.
  • Picture Viewer: Lets you store and display photos. Some trail receivers also have cameras.
  • POI: Points of Interest. These are locations of places saved in a street GPS's memory, including businesses and public facilities. All street GPS receivers have databases of thousands or millions of POI's. This feature means you can locate a place by name or category rather than having to know the street address.
  • Powered Mount: The power/USB cable goes to the mount instead of the GPS receiver, so you don't have to connect the cable every time you mount the GPS unit.
  • Preloaded Maps: These maps are loaded into the unit at the factory and give coverage of a specific area at much more detail than the basemap. Trail units typically have topographic maps at a scale of 1:100,000 or better. Street GPS receivers typically have street and road maps covering a country or a region, such as the United States, North America, or Europe.
  • Profiles: Stores configurations for activities such as hiking, geocaching, cycling, driving, and others, saving you the trouble of changing many settings when switching uses.
  • QWERTY or ABC Keyboard: Lets you choose the layout of the virtual keyboard on the touchscreen.
  • Raster Maps: Maps created by scanning printed maps. For example, raster USGS 7.5-minute series topographic maps are the most detailed and accurate maps of U.S. terrain available, but man-made features such as roads and trails are not always up to date.
  • Route: Routes are made up of two or more waypoints that describe a route of travel and can be saved in the GPS receiver with a descriptive name. All trail GPS receivers allow you to store multiple routes, as do some street GPS units.
  • Route Avoidance: Allows you to set a street GPS receiver to avoid toll roads, highways, and other undesirable routes.
  • Route Setup: Enables a street GPS to calculate routes by the least time, shortest distance, or off road.
  • Saved Geocaches: In the GPS receiver, a geocache is a waypoint with special geocaching features such as marking the cache as found and the ability to take notes.
  • Selective AvailabilityWhen the US GPS system first went active, the DOD intentionally degraded the accuracy of the civilian signal, so as to deny any potential enemies the full accuracy of the system. (The military used an encrypted signal.) With the growing dependence of the public on GPS and the widespread availability of civilian differential GPS systems which could correct even degraded SA signals to accuracies of a few mm, there was no point to SA. It was turned off in 2000, and the current GPS satellites don't have SA capability. Meanwhile, the US military has developed battlefield GPS jamming systems. The Russian GLONASS and European Galileo systems operate at full civilian accuracy at all times- but all three systems have encrypted services that are more accurate than the public services.

  • Smartphone Link: Links to selected smartphones and uses their Internet connection to obtain real-time traffic information and other updates.
  • Smart Traffic: This street GPS feature uses historic traffic information such as average speeds during rush hour periods to adjust travel times.
  • Speed Limit Display: Shows the posted speed limit along major roads and may also warn you if you exceed the limit. Temporary speed limits such as construction zones are typically not shown.
  • Spoken Street Names: In addition to voice prompts, many street GPS receivers also speak the street names, which completely eliminates the need to look at the screen during critical phases of driving.
  • SPOT: SPOT capability allows you to transmit messages containing your GPS location through the SPOT satellite service via a paid subscription. Messages include SOS, OK, and custom messages. Friends also can track your progress on Google Maps.
  • Sun and Moon Data: Many trail GPS receivers can display the times of sunrise, sunset, moonrise, and moonset for any location, which is useful for backcountry trip planning.
  • Tides: This feature shows tide graphs for tide stations and is essential for coastal boaters and sea kayakers.
  • Touchscreen: All street GPS receivers and some trail units have touch-activated screens. They are best for use in-vehicle and for mild hiking conditions. Most touchscreen trail units will not work when you're wearing gloves or when the unit is protected inside a waterproof bag.
  • Track Log: Trail GPS receivers can be set to automatically store waypoints as you travel, creating a track log that can be saved and also used to backtrack your route.
  • Traffic: This street GPS feature lets you see real-time traffic data, such as congestion and accidents. May require a monthly or annual fee.
  • Trucking Features: Street GPS receivers optimized for trucking and RV use. They usually have larger screens, louder speakers, and truck-specific speed limits, routing and POI's. RV drivers can set vehicle profiles so that routes are calculated that meet height, width, and weight limits. Data logging lets you track hours and fuel use.
  • User Route Prediction: Allows a street GPS to take into account user preferences when computing a route to the chosen destination.
  • Vector Maps: Digital maps created on a computer or GPS screen from mapping data. Topographic vector maps are not as accurate as USGS topo maps in depicting terrain features, but trails, roads, and other man-made features are often more up to date.
  • Voice-Activated Navigation: Allows you to give spoken commands to a street GPS receiver.
  • Voice Prompts: Most street GPS receivers use a small built-in speaker to give voice driving directions. This feature is essential to avoid driver distraction caused by looking at the GPS screen.
  • WAAS: TheWide Area Augmentation System is a differential GPS (DGPS) system run by the Federal Aviation Administration to enhance GPS accuracy to one to three meters for air navigation. It uses geosynchronous satellites to send correction signals to the GPS receiver. Nearly all trail GPS receivers have WAAS.
  • Waterproof Standards: IPX7 is the common standard for GPS receivers, meaning the unit can be submerged in one meter of water for up to 30 minutes. Trail, motorcycle, bicycling, and boating GPS receivers should be waterproof.
  • Waypoint: A physical location described by coordinates and labeled with a name, also called a "location" or a "favorite." All GPS navigation takes place between waypoints saved in the receiver.
  • Wi-Fi: This lets you download software updates wirelessly without having to connect to a computer. You can also share data with other users, and have your receiver updated with geocache data automatically.
  • Wireless Data Sharing: This feature lets you share GPS data such as waypoints with another compatible GPS unit.
  • XM Compatible: Capable of receiving XM Satellite Radio and weather maps with an optional subscription.