A complete listing of the terms and phrases used with GPS units.
Acquisition Time – Amount of time required for a GPS unit to lock onto three satellites to provide a 2-D fix of present position.
Area calculation – Measuring tool uses coordinates to accurately determine the size of irregular-shaped areas. The feature proves indispensable for tasks like calculating how much seed or fertilizer is needed for food-plot coverage.
Barometric sensor – Internal barometric altimeters more accurately determine altitude readings. This feature is beneficial when used in conjunction with topo maps. Altimeters can also be used to determine weather trends.
Basemaps – Basemaps are built-in maps on a GPS unit. A typical basemap will show interstates, state highways, major metro thoroughfares, cities, airports, lakes, rivers and exit information such as restaurants, hotels and gas stations. Basemaps are great for road travelers who need to know distances and locations of basic places. Outdoor enthusiasts can use this information to give them reference points to local cities and distances to major lakes and rivers. Some models come pre-loaded with advanced maps ready to use right out of the box.
Built-in camera – Capture a picture on a GPS with a built-in digital camera and the exact coordinates will be embedded on that image using geotags. If you want to return to the same spot 20 years later, the geotagged picture will take you right there. Once the image is saved on your GPS, it can be seamlessly transferred to compatible mapping software.
Bearing (BRG) – The precise compass direction (in degrees) from your present position to the next waypoint. (Readings are selectable in either degrees magnetic or true north.)
Cold Start – The process of powering up a new GPS receiver for the first time and having it search out and lock onto the satellites by itself, without the benefit of initialization data. This procedure is slower and may require up to eight minutes for initial satellite acquisition only.
Course Over Ground (COG) – The current direction (in degrees) that you are actually traveling. (Again selectable in degrees magnetic or true north.)
Cross Track Error (XTE) – Digital reading on GPS steering screens that indicates precisely how far off you are, to the right or left of the center of the course.
Data cards – Built-in data ports accept SD cards and other similar storage devices, allowing you to play MP3s or check game-camera pictures in the field.
Differential GPS (DGPS) – A system devised initially by the U.S. Coast Guard to improve GPS accuracy levels to within 5 meters. It employs a land based, fixed position, DGPS reference receiver to first calculate the Selective Availability errors, then transmit the necessary correction factors to mobile GPS receivers in the area. DGPS system does require an added beacon receiver to communicate with the standard GPS unit.
Distance To Go (DTG) – Digital readout (selectable in miles, nautical miles or kilometers) displayed only when navigating to a waypoint. It simply indicates the remaining distance from your present position to the next waypoint.
Event Marker/Icon – A graphic symbol that can be placed on the plotter screen (and saved in memory) to represent some special event or area of interest to the GPS user.
Electronic Compass – The compass feature on many GPS units only offers a heading while it is moving. Once a GPS unit becomes stationary, the compass fails to operate accurately. To compensate for this, some manufacturers have included an electronic compass, which operates while it is stationary. Having an electronic compass eliminates the need to carry along a separate compass for navigation and will provide immediate, accurate directions. Most units must be quickly calibrated the first time they are used or whenever new batteries are installed.
Geocaching – Best described as a high-tech game of hide and seek. Participants use their GPS to find hidden containers called geocaches, usually a waterproof container with an item or items and a logbook inside. The items are usually small and are not high in monetary value, but may be of personal value to the finder. A geocacher hides the items and records the coordinates. Other geocachers plug these coordinates into a GPS to find the geocache and then record it in the logbook and online. Most GPS units can be used for geocaching.
Initialization – Refers to the simple procedure of telling a new GPS receiver where it is, when it is turned on for the first time. Required information includes: approximate present position in latitude/longitude coordinates; and the current local time and date.
Multiplexing Receiver – GPS receiver that rotates a small number of channels to multiple satellites in order to provide current positioning data. Typically, multiplexing receivers require more time for satellite acquisition and lock on, and are not as accurate as parallel channel receivers. Multiplexing receivers are also more prone to lose satellite fix in dense woods compared to parallel channel GPS receivers.
Parallel Channel Receiver – GPS receiver that simultaneously tracks multiple satellites to provide the fastest, most reliable and accurate navigational data, under the most adverse conditions.
Pixel – A picture element; the "building blocks" of a liquid crystal display (LCD). The greater the number of vertical and horizontal pixels, the better the screen resolution and detail.
Plotter Display – Provides an overhead bird’s-eye view of your current position relative to the waypoints and even marker/icons you have saved. A dotted line marks the shortest route to the chosen waypoint, and a recorded plot trail displays the path you have taken so far.
Position Display – One of the primary navigational data screens that emphasize the present position in latitude/longitude coordinates, as well as other helpful navigational information.
Present Position – Current location on the face of the Earth, in terms of the specific latitude/longitude coordinates, displayed in degrees, minutes, and thousandths of a minute.
Programmable Windows – The ability to customize existing split panel window grouping with specific combinations of navigational data.
Route – Consists of two or more waypoints combined in a course of travel. It provides the automatic capability to navigate through several waypoints, without having to reprogram the unit after arriving at each one. Once programmed into the GPS unit, the route provides the option of navigating forward through the waypoints or in reverse order.
Satellite Status Display – An information screen that shows technical data about each satellite in view. Information includes receiver channel numbers; actual satellite I.D. numbers; status of satellite tracking (T) or searching (S); satellite elevations and azimuths; signal to noise ratios (SNR) (the higher the number, the better); and dilution of precision ratings (GDOP is most important; the smaller the number, the better potential accuracy).
Savable Plot Trails – The capability to save your actual plot trail created on the plotter screen, thereby enabling the GPS user to either backtrack the course immediately, or save and retrace the trip at a later time.
Selective Availability (S/A) – The system used by the U.S. Department of Defense to intentionally degrade the accuracy of satellite GPS signals being transmitted to civilian GPS receivers. With random S/A on, the government guaranteed that civilian GPS accuracy levels would be 100 meters or less, 95% of the time. S/A was eliminated May 2, 2000. Accuracy levels are now within 10 to 20 meters.
Speed Over Ground (SOG) – Digital reading that indicates your current ground speed. (Selectable in miles per hour, knots or kilometers per hour.)
Steering Screen – Shows a graphic "highway view" of the GPS user’s course over ground. Provides helpful instructions as to how far off course, which direction to steer, right or left, to make corrections and displays related navigational data pertaining to a waypoint.
Straight Line Navigation – The standard method of navigation used by recreational GPS products. When commanded to navigate to a waypoint, the unit draws a straight, dotted line from the present position to the selected waypoint. It’s the shortest, most direct route to the destination. Caution: Straight line navigation does not take into account any obstacles in the path; interim waypoints may be required to navigate safely around obstacles.
Time To Go (TTG) – Digital reading showing the time remaining from your current position to the next waypoint. This function takes into account your Distance To GO (DTG) and your Velocity Made Good (VMG) to give you as closely as possible the amount of time left to reach your waypoint. Displayed in hours, minutes and seconds, it will continue counting down until the waypoint is reached.
Track Logs – While traveling, GPS units can record the path you take in a track log. Every twist and turn you take along a trail or road will be stored, leaving an "electronic bread-crumb trail." This allows you to see exactly where you have been during your travels. A track log can be activated into a reverse route and will automatically set enough waypoints along the track log to guide you back to your original starting point. This track log can be saved as a route so you can use it whenever you need to.
Trip Computers – The functions on a trip computer will vary greatly based on the model and design. For the most part, a trip computer will provide maximum and average speeds of travel, and trip timers and distances. These features will show you how far and how long it will take you to make it to the next city, hotel, hunting camp or any other waypoint you have set as a destination.
True and Magnetic North – True north is the top of the world, where all lines of longitude converge. Magnetic north is the location our compasses point to; it lies several hundred miles to the south of true north, at a location in Canada.
Two-way radio/GPS combos – These units combine the navigation of a GPS with the communication of a two-way radio. The two-in-one convenience frees up space in your pack. Peer-to-peer positioning “beams” your location to another user within a two-mile range. This shows the receiving party the exact distance and bearing from your position to theirs. These devices are not legal for hunting in all states. Be sure to check your state’s regulations.
Turn-by-turn directions – Like their automotive counterparts, some handheld GPS models are turn-by-turn capable with the purchase of additional software. Consider one of these units if you want a GPS with the versatility to navigate in the field and on the road.
Velocity Made Good (VMG) – Digital speed reading (similar to SOG) that compensates for progress being made toward a waypoint. For example, when traveling directly on course toward a waypoint, the SOG and VMG readings may match. However, when traveling off course, the VMG reading will typically be slower than the SOG. VMG is a true indication of the speed being made to the selected waypoint.
Waypoint – Location, spot or destination (latitude/longitude) that can be stored in memory to be recalled and used at a later time for navigation purposes. Simply think of it as an electronic address.
WAAS – WAAS (or Wide Area Augmentation System) was developed by the Federal Aviation Administration for pilots traveling in adverse weather conditions. WAAS operates from 25 networked ground reference stations. Much like the DGPS, these reference stations receive signals from the satellites and correct any errors. But instead of transmitting these corrections to a separate DGPS receiver, the corrections are sent back to the satellites, which can then transmit the correct information directly to your GPS unit. WAAS can greatly increase accuracy down to 3 meters. Most GPS models for use in North America now come standard with WAAS capabilities.
Wireless data sharing – Similar to sending texts or pictures between cell phones, GPS models with wireless sharing allow you to transmit saved data, such as waypoints, to another similarly equipped unit within range.