AMPS: Analog Mobile Phone System. Non-digital cellular mobile phones.

Altimeter: an instrument that measures altitude or elevation with respect to a reference level, usually mean sea level, by means of air pressure.

Azimuth: An azimuth is often designated as true, magnetic, compass, grid, or relative as the reference direction is true, magnetic, compass, grid north, or heading, respectively. Azimuth is the direction of a horizontal line as measured on an imaginary horizontal circle. The horizontal direction reckoned clockwise from the meridian plane of the observer, expressed as the angular distance between the vertical plane passing through the point of observation and the poles of the Earth and the vertical plane passing through the observer and the object under observation.

BMP: Bitmapped image format (Microsoft® Corp.) BMP was developed by Microsoft and is the native graphics format for Windows.

BSB Chart: BSB Electronic Charts was a company that held the exclusive license from the U.S. Department of Commerce, NOAA to develop and license electronic versions of NOAA nautical charts. Maptech now holds this license and refers to the BSB charts as the Chart Kit format. The BSB charts are in a proprietary format. Northport Systems Inc., the creator of Fugawi, has been licensed by NOAA and BSB Electronic Charts (now Maptech) to create BSB-compatible software and BSB charts in Europe and Canada. Nautical Data International, Inc. holds the exclusive license to produce Canadian electronic nautical charts, which are also available in BSB format.

Bearing: a horizontal angle, measured from 0 to 90 degrees, fixing the direction of a line or direction of travel with respect to either a north or south direction.

Bench mark: a relatively permanent material object, natural or man-made, with a known elevation. A bench mark can be used as a reference point when navigating a route or in determining the elevation of nearby land features.

Bitmapped Image: A bitmapped image is one made from an array of dots rather than continuous lines or areas.

CIB: Controlled image base

CITS: Close Air Support Integrated Targeting System (CITS) is a program developed by Northport Systems Inc. for integrating the Global Positioning System (GPS) with laser target locators.

ChartTiff: ChartTiff maps are collarless DRGs. ChartTiff raster images allow for easy panning from one map to another, without worrying about map overlap. The U.S. topographic maps in ChartTiff format are converted to UTM projection.

Contour line: a line on a map that connects points of equal elevation. The vertical distance between contour lines is equal to the contour interval.

Course Over Ground (COG): the direction, reported in true or magnetic north values, in which a GPS receiver and the person operating it are moving with respect to the earth.

DDE: Dynamic Data Exchange. A Windows protocol that allows communication between applications. When information is updated in one application, related information will be updated in other applications.

DRG: Digital Raster Graphic. The United States Geological Survey is releasing digital versions of all of the topographic maps. These files are called Digital Raster Graphics (DRG) maps. The images themselves are stored in a format called GeoTiff.

Datum: a reference system for surveying which involves using a plane, level, line, etc., from which to calculate heights and depths. A vertical datum is a level surface to which heights are referred. The horizontal datum is used as a reference for position.

Elevation: the vertical distance of a point above or below a reference surface, such as sea level.

Ephemerides: Data giving the location of satellites for each day of the year or for other regular intervals.

GIF: Graphics Interchange Format. This is a format for saving graphics files with data compression.

GLL: A data sentence that is part of the NMEA protocol for transferring information between electronic devices. The GLL sentence contains position information.

Global Positioning System (GPS): a global navigation system that is based on triangulation from a constellation of 24 satellites orbiting the earth. A GPS receiver pinpoints its position on earth by measuring its distance from the satellites. It does so by calculating the time it takes for a coded radio message to pass from the satellite to the GPS unit. A GPS unit needs at least three measurements to determine its exact position.

Ionosphere: That part of the atmosphere, extending from about 70 to 500 kilometers, in which ions and free electrons exist in sufficient quantities to reflect electromagnetic waves.

JPG: Joint Photographic Experts Group Format. Standard format for image storage created by this group. JPG allows large images to be significantly compressed. Along with the GIF format, it is one of the most common and widely supported image formats used for raster graphics.

Latitude: the distance north or south of the equator of a point on the earth's surface. This distance is measured in degrees, minutes, and seconds. Lines (parallels) of latitude circle the earth horizontally and are parallel to one another. One minute of latitude equals one nautical mile.

Longitude: the distance east or west of the prime meridian of a point on the earth's surface. Longitude is measured in degrees, minutes and seconds. Lines (meridians) of longitude create a geographic grid around the world and are not parallel, but rather converge at the poles.

MOB: Man-over-board

Magnetic north: the area to which all compass needles point, located roughly 1300 miles south of true north. Magnetic north moves west slightly each year due to the earth's rotation and the friction created between the earth's liquid center and its solid crust.

Map projection: the systematic arrangement of the earth's spherical or geographic coordinate system onto a plane; the process of transforming a globe into a flat map with the least amount of distortion; a transformation process.

Meridian: an imaginary line that circles the earth, passing through the geographic poles and any given point on the earth's surface. All points on a given meridian have the same longitude.

NMEA: National Maritime Electronics Association. The association sets standards for interfacing nautical electronic devices, including Global Positioning System receivers.

PCMCIA Card: Personal Computer Memory Card International Association Card. A Sunnyvale, California nonprofit trade association created to standardize the connection of peripherals to portable computers. PCMCIA developed the PCMCIA card, a lightweight, removable module about the size of a credit card that adds features to a portable computer.

PCX: PCX is a graphics file format for graphics programs running on PCs. It is supported by most optical scanners, fax programs, and desktop publishing systems.

PNG: Portable Network Graphics. A file format for the portable, well-compressed storage of raster images.

Packet Messaging: Radio transmitted message system.

Pixel: Picture element. Definable locations (dots) on a display that are used to form images on the screen.
Position fixing: determining your position on a map in terms of its coordinate system. This can be done visually, by referencing the terrain and comparing it to contour lines and other map features, by using a GPS receiver.

Prime meridian: a meridian of longitude 0 degrees that runs through Greenwich, England, and is used as the origin for measurements of longitude.

RMS: Root Mean Square. The standard deviation of the error in the GPS location.

Raster: Computer graphics term describing a predetermined pattern of line that provides uniform coverage of a display space. Raster graphics are computer graphics that are composed of an array of pixels arranged in rows and columns.. Raster maps are stored as a series of pixels. Vector maps are stored as line segments.

Relief: changes in terrain; elevations or depressions in the land.

Relief shading: a technique for showing the ups and downs of the land portrayed on a topographic map. The process makes land look three-dimensional by the use of graded shadow effects. Traditionally, maps are shaded as though the light source is coming from the northwest.

Scale: the distance between two points on a map as they relate to the distance between those same points on the earth.

Sighting line: The line that you sight along to take a bearing.

Slope: When land deviates from the horizontal plane it has slope. On a topographic map, the closer the contour lines are placed together, the greater the slope of the land being portrayed.

Tif: Tagged image file format. One of the most widely supported file formats for storing bit-mapped images on personal computers (both PCs and Macintosh computers).

Topography: relief of the land surface; the graphic portrayal of that relief in map form by the use of contour lines.

Troposphere: The portion of the atmosphere from the earth's surface to the stratosphere; that is, the lowest 10 to 20 kilometers of the atmosphere.

True north: the geographical North Pole.

USGS: United States Geological Survey.

Universal Transverse Mercator grid (UTM): a grid coordinate system that appears on most USGS maps. It provides a perpendicular grid with constant linear surface distance values between each of its grid lines in all directions, except near the poles. The UTM system divides the area of the earth between 84 degrees N and 80 degrees S into 60 zones. While coordinates reported in degrees, minutes, and seconds of latitude and longitude are often called true coordinates, those reported in terms of the UTM grid are referred to as false eastings and northings.

Vector: Images defined by sets of straight lines that are defined by the locations of the end-points. Vector graphics require much less storage space than raster or bitmapped graphics.

Waypoint: A predetermined geographical position used for navigation along a route or for storing the position of a particular feature.