Glossary

Glossary

2D OPERATING MODE A positional fix that includes only Longitude and Latitude. This is due to a weak lock and is generally only present when the minimum satellite count (3) required for a positional fix is providing information.	3D OPERATING MODE A positional fix that includes Longitude, Latitude, plus elevation.	ACCURACY The value of how close the estimated position is as provided by a positioning system is from the real location.	ACQUISITION TIME The time it takes the antennae to acquire ample signal to attain a lock and begin supplying positional data.
ALMANAC DATA Information transmitted by each satellite on the orbits and state (health) of every satellite in the specific GNSS constellation. Almanac data allows the receiver to rapidly acquire satellites shortly after it is turned on.	ALTIMETER An instrument for determining elevation, The Bad Elf Pro+ and Surveyor models contain a digital barometric altimeter as a secondary source of elevation data.	COLD START In this state, the receiver has no information from the last position (e.g. time, velocity, frequency, etc.) at startup. Therefore, the receiver must search the full time and frequency space and all possible satellite numbers. If a satellite signal is found, it is tracked to decode the ephemeris (18-36 seconds under strong signal conditions), whereas the other channels continue to search satellites. Once there is a sufficient number of satellites with a valid ephemeris, the receiver can calculate position and velocity data.	COORDINATE SYSTEMS A system that enables every location on the Earth to be specified by a set of numbers, letters, or symbols. The coordinates are often chosen such that one of the numbers represents the vertical position, and two or three of the numbers represent the horizontal position. A common choice of coordinates is latitude, longitude, and elevation. Longitude/Latitude can further be described in different formats i.e. Decimal Degrees, Degrees Decimal Minutes, and Degrees Minutes Seconds
DATUM A mathematical model of the earth that is used in mapping, consists of a series of parameters that define the shape and size of the ellipsoid and its orientation in space. WGS84 is the common datum used by GPS because of its global accuracy across the breadth of the earth.	DIFFERENTIAL GPS (DGPS) An extension of the GPS system that employs local beacons to transmit position corrections to GPS receivers. DGPS reduces the determinantal effects of ionosphere, propagation delay, etc., and can improve position accuracy greatly.	DILUTION OF PRECISION (DOP) The measure of the effect satellite geometry has on positional measurement precision.. A lower DOP value indicates better relative geometry and higher corresponding accuracy.	ELEVATION The distance above or below mean sea level.
ELLIPSOID A geometric surface similar to a sphere, but reflecting some lengthening or flattening along one or several of the main axis The many datums that define the model of the earth all represent a variety of ellipsoids.	EPHEMERIS DATA Current satellite position and timing information transmitted as part of the satellite data message. Ephemeris data is valid for several hours and speeds up the acquisition process of satellites for the positional lock.	FREQUENCY The number of repetitions per unit of time. The standard unit of Frequency the Hertz(Hz) is 1 sample/sec. I.e 5Hz = 5 samples/sec, 1Hz = 10 samples/sec	GEODETIC DATUM A mathematical model representing the size and shape of the earth.
GEOGRAPHIC INFORMATION SYSTEM (GIS) A system designed to capture, store, manipulate, analyze, manage, and present all types of spatial or geographical data. The term GIS is often expanded beyond this simple definition to include the computer system, software, data collection equipment, personnel, and actual data employed in the process.	GLOBAL POSITIONING SYSTEM (GPS) A global navigation system based on 24 or more satellites, currently 32 with several as inactive replacements, circling the earth in Medium Earth Orbit (MEO) providing precise, worldwide positioning and navigation information.	GLONASS The Global Orbiting Navigational Satellite System (Глобальная навигационная спутниковая система); the Russian counterpart to the United States’ GPS system. Currently, 24 satellites offer similar accuracy and worldwide coverage	GLOBAL NAVIGATION SATELLITE SYSTEM (GNSS) System of satellites that provide autonomous geo-spatial positioning with global coverage. GPS (United States) and Glonass (Russia) are the two commonly referenced systems. Other systems are being expanded or being brought online in the near future including Beidou (China) and Galileo (E.U.).
HEADING The direction of travel as provided by a compass, while similar this is different than track.	HOT START In Hot start, the receiver was powered down only for a short time ago (4 hours or less). The ephemeris is still valid, since the receiver doesn't need to download ephemeris again the expected time to first fix is <5s, this is the fastest startup method.	INITIALIZATION The first time a GPS receiver orients itself to its current location and collects almanac data. After initialization has occurred, the receiver remembers its location and acquires a position more quickly because it knows which satellites to look for.	L1 FREQUENCY One of the two radio frequencies transmitted by the GPS satellites. This frequency carries the Coarse Acquisition Code (C/A code), P-Code, and the nav message, and is transmitted on a frequency of 1575.42 MHz.
L2 FREQUENCY One of the two radio frequencies transmitted by the GPS satellites. This frequency carries only the P-Code, and is transmitted on a frequency of 1227.6 MHz.	L BAND The radio frequencies extend from 390 MHz to 1550 MHz. The GPS carrier frequencies are in the L band (1227.6 MHz and 1575.42 MHz). GLONASS frequencies are also in the L band (1246 MHz and 1602.0 MHz) … it’s one L of a band!	LATITUDE A position's distance north or south of the equator, measured by degrees from zero to 90. One minute of latitude equals one nautical mile.	LINE OF SIGHT (LOS) Transmission and reception of data can only occur where the respective stations are in view of each other without any sort of obstacle between them. FM radio, microwave, and satellite transmission are examples of line-of-sight communication.
LONGITUDE The distance east or west of the prime meridian.	MAGNETIC DECLINATION The degree of separation in degrees between true north and magnetic north at a specific location.	MAGNETIC NORTH The direction from your current location to the north magnetic pole. This is the North that is referenced by the needle on a compass.	MEAN SEA LEVEL The average level of the ocean's surface, as measured by the level halfway between mean high and low tide. Used as a standard in determining land elevation or sea depths. Please don’t measure sea depths with your Bad Elf.
MULTIPATH ERROR Error is caused when the same satellite signal reaches the GPS receiver antenna by more than one path. Usually caused by the reflection of the signal from a large flat surface in the vicinity.	NAUTICAL MILE One of several units of measure found in our app and on our devices, It is equal to 1,852 meters (about 6,076 feet).	NMEA SENTENCES A specification for communication between marine electronic devices such as echo sounders, sonars, anemometers, gyrocompass, autopilot, GPS receivers, etc. It has been defined by and is controlled by, the U.S.-based National Marine Electronics Association.	POSITION An exact, unique location based on a geographic coordinate system.
POSITION FIX The process of a GPS receiver attaining ample satellite data to provide position. This can also reference the computed position coordinates as provided by the GPS receiver.	POSITION FORMAT The way in which the GPS receiver's position will be displayed on the screen. Commonly displayed as latitude/longitude in degrees and minutes, with options for degrees, minutes and seconds, degrees only, or one of several grid formats.	PSEUDORANDOM- CODE The identifying signature signal transmitted by each GPS satellite and mirrored by the GPS receiver in order to separate and retrieve the signal from background noise.	PSEUDORANGE The measured distance between the GPS receiver and the GPS satellite using uncorrected time comparisons from satellite-transmitted code and the local receiver's reference code.
REAL-TIME KINEMATIC (RTK) A technique used to enhance the precision of position data derived from satellite-based positioning systems (global navigation satellite systems, GNSS) such as GPS, GLONASS, Galileo, BeiDou, and GAGAN. It uses measurements of the phase of the signal's carrier wave, rather than the information content of the signal, and relies on a single reference station or interpolated virtual station to provide real-time corrections, providing up to centimetre-level accuracy.	REAL-TIME CORRECTION MESSAGES (RTCM) The defined differential data protocol for relaying GPS correction messages from a base station to a field user. Developed by the Radio Technical Commission for Maritime Services ( also RTCM), a nonprofit scientific and educational organization that serves all aspects of maritime radio communications, radio navigation, and related technologies	SERIAL COMMUNICATION Process of sending data one bit at a time, sequentially, over a communication channel or computer bus.	TIME TO FIRST FIX (TTFF) Amount of the time required for a GPS receiver to acquire satellite signals and navigation data, and calculate a position solution.
TRACK Direction of travel based on a calculated vector of movement.	TRUE NORTH The direction from a location to the North Pole, not the magnetic pole. Despite what our resident Canadian will tell you, not a direct reference to Canada.	WIDE AREA AUGMENTATION SYSTEM (WAAS) The local SBAS system to North America. Incorporating a system of ground stations to make corrections to known errors in the GPS signal relaying these through an ancillary set of satellites to an enabled device. A WAAS lock is capable of 2.5m horizontal accuracy 95% of the time.	WGS-84 WGS84 is the standard U.S. Department of Defense definition of a global reference system for geospatial information and is the reference system for the Global Positioning System (GPS). Specifically, WGS84 is an Earth-centered, Earth-fixed terrestrial reference system and geodetic datum.