Popular terms used throughout this website



The regions of the electromagnetic spectrum that are relatively free from the effects of atmospheric attenuation. Radiation in these wavebands will pass through the atmosphere with less modification than radiation at other wavelengths.


The horizontal direction of a vector, measured clockwise in degrees of rotation from +ve y-axis for eg. degrees on a compass. The direction of one object from another usually expressed as an angle in degrees relative to true north. Azimuths are usually measured in clockwise direction, thus an azimuth of 90 degrees indicate that the second object is due east from the first.


Angular displacement from North.


Also known as Planar Projections) A class of map projections that are constructed by placing a flat planar surface tangent to a single point on the globe, or by placing the globe to an intersecting (secant) plane. With azimuthal (or planar) projections, lines of equal distortion are concentric around the point of tangency or the center of the circle of intersection. Most azimuthal maps do not have standard parallels or standard meridians. Each map has only one standard point: the center. Thus, the azimuthal projections are suitable for minimizing distortion in a somewhat circular region, such as Antarctica, but not for an area with predominant length in one direction. Azimuthal projections include Orthographic, Stereographic, Gnomonic, Lambert Azimuthal Equal-Area, and Azimuthal Equidistant.


A range of wavelengths of electromagnetic radiation. Remote sensing devices commonly collect images in discrete bands, such as visible red, green, and blue, and the invisible near-infrared.


An image format that stores each band of data collected by multispectral satellite scanning instuments in a separate file.


A measure of the volume of data that can flow through a communications link. image data tend to exist as large datasets; thus moving image data sets from one computer to another requires high bandwidth or performance will be slowed. Also known as through put.


Science of measuring water depths (usually in the ocean) to determine bottom topography.


Relatively permanent material object, natural or artificial, bearing a marked point whose elevation above or below an adopted datum is known.


Material object placed on or near a boundary line to preserve and identify the location of the boundary line on the ground.


Survey made to establish or to reestablish a boundary line on the ground, or to obtain data for constructing a map or plat showing a boundary line.


Creating and/or adding points in a vector object from imported coordinate data (like text files that contain pairs of coordinates, or database files with fields representing pairs of coordinates).


Survey relating to land boundaries, made to create units suitable for title transfer or to define the limitations of title. Derived from "cadastre" meaning a register of land quantities, values, and ownership used levying taxes, the term may properly be applied to surveys of a similar nature outside the public lands, such surveys are more commonly called "land surveys" or "property surveys." 


The process of choosing attribute values and computational parameters so that a model properly represents the real world situation being analyzed. For e.g. in path-finding & allocation, calibration generally refers to assigning or calculating appropriate value to be entered in impedance and demand items. 


Science and art of making maps and charts. The term may be taken broadly as comprising all the steps needed to produce a map: planning, aerial photography, field surveys, photogrammetry, editing, color separation, and multicolor printing. Mapmakers, however, tend to limit use of the term to the map-finishing operations, in which the master manuscript is edited and color separation plates are prepared for lithographic printing.