Azimuth

A mathematical concept defined as the angle, usually measured in degrees (°), between a reference plane and a point.

Datum

A set of reference points on the earth's surface against which position measurements are made, and often an associated model of the shape of the earth (ellipsoid) to define a geographic coordinate system.

Digital Elevation Model (DEM)

A digital model or 3D representation of a terrain's surface such as the Earth, moon or asteroid created from terrain elevation data.

Digital Terrain Elevation Data (DTED)

A standard of digital datasets which consists of a matrix of terrain elevation values. DTED was originally developed in the 1970s as a standard to support aircraft radar simulation and prediction, and supports many applications including line-of-sight analyses, terrain profiling, 3-D terrain visualization, mission planning/rehearsal, and modeling and simulation. DTED is a standard National Geospatial-Intelligence Agency (NGA) product that provides medium resolution, quantitative data in a digital format for military system applications that require terrain elevation. DTED has three levels: DT0, DT1, and DT2. Level 0 has a post spacing of ca. 900 meters; Level 1 has a post spacing of ca. 90 meters; Level 2 has a post spacing of ca. 30 meters.

Ellipsoid

A type of quadric surface that is a higher dimensional analogue of an ellipse.

GeoMark

The TerraGo component that stores location, attribute, and hyperlink data in a GeoPDF file. TerraGo software such as the GeoPDF® Toolbar collects GeoMarks and displays them in a GeoPDF file.

GeoPDF

The TerraGo published extension to the standard Adobe PDF file format. GeoPDF is used to present GIS and mapping data as well as other advanced PDF features such as layers and object data. GeoPDF adds a coordinate transformation matrix and other metadata to allow transformation of PDF coordinates to a projected Cartesian coordinate system.

GeoPDF index map

A GeoRegistered PDF file that is used as the map where the grid is drawn and hyperlinks are inserted that link to other more detailed GeoPDF maps.

GeoRegistered

The process of adjusting on one drawing or image to the geographic location of a 'known good' reference drawing, image, surface or map.

Geospatially-aware PDF

A PDF file based on the proposed ISO 32000 constructs for GeoRegistration or advanced features such as compressed object streams.

GPS (Global Positioning System)

The only fully functional Global Navigation Satellite System (GNSS) that uses a constellation of at least 24 Medium Earth Orbit satellites that transmit precise microwave signals, allowing  a GPS receiver to determine its location, speed, direction, and time.

LIDAR

Light Detection And Ranging. Optical remote sensing technology that can measure the distance to, or other properties of, targets by illuminating the target with laser light and analyzing the backscattered light.

Log ASCII Standard (LAS)

A file format for the interchange of LIDAR data.

Magnetic bearing

A device to permit constrained relative motion between two parts where the load is supported by magnetic fields.

MapBook

A collection of GeoPDF files that contain bookmarks and hyperlinks that are bound together by hyperlinks to an index map.

Map definition file

A file in .csv or .xml format that contains the coordinate pairs of the four corners of each PDF file to be GeoRegistered.

Map series file

A file in .xml or .csv format that contains a list of GeoPDF files /geospatially-aware PDF files included in the TerraGo MapBook and the values used for the index map labels and hyperlinks.

National Marine Electronics Association (NEMA)

A combined electrical and data specification for communication between marine electronic devices such as echo sounder, sonars, Anemometer (winds speed and direction), gyrocompass, autopilot, GPS receivers and many other types of instruments.

Neatline

The border delineating and defining the extent of geographic data on a map; it demarcates map units so that, depending on the map projection, the neatline does not always have 90-degree corners; the most accurate element of the data because the neatline is never adjusted.

Polygon

A plane figure that is bounded by a closed path or circuit, composed of a finite sequence of straight line segments.

Polyline

A continuous line composed of one or more line segments.

PRJ

A projection format file; the ESRI shapefile supporting file that contains the coordinate system and projection information.

Projection

Any method used in cartography to represent the two-dimensional curved surface of the earth.

TIF or TIFF

Tagged Image File or Tagged Image File Format--a file format widely supported by image-manipulation applications, by publishing and page layout applications, by scanning, faxing, word processing, optical character recognition and other applications. As of 2009, it is under the control of Adobe Systems.

Universal Transverse Mercator (UTM)

A grid-based method of specifying locations on the surface of the Earth; not a single map projection, rather, the system employs a series of sixty zones, each of which is based on a specifically defined secant transverse Mercator projection.

UTF-8

A variable-length character encoding method for Unicode that represents every character in the Unicode character set. It also has the special property of being backwards-compatible with the ASCII encoding scheme, which is based on the ordering of the English alphabet.

WGS84

World Geodetic System of 1984; a datum based on the GRS80 spheroid.

Well-Known-Text (WKT)

A text markup language for representing vector geometry objects on a map, spatial reference systems of spatial objects and transformations between spatial reference systems.