Glossary Aerial triangulation The process of finding the exterior orientation parameters of a block of aerial photos/images using a (very) limited number of ground control points. Aerosol
A suspension of fine solid (dust) or liquid particles (water) in a gas (air).
Affine transformation A 2D geometric transformation (plane-to-plane transformation) that uses six parameters to account for rotation, translation, scale change, and shearing. It defines the (linear) relationship between two coordinate systems such as an image coordinate system and a map coordinate system; see also conformal transformation. Agent-Based Model (ABM) These attempt to model processes in the form of multiple (possibly interacting) agents (which might represent individuals) using sets of decision-rules about what the agent can and cannot do. As such, a key notion is that simple behavioural rules for individual agents generate complex behaviour for the entire ‘system’. Agent-based models have been developed to understand aspects of complex systems, for example by incorporating stochastic and or deterministic components. Algorithm
A procedure for solving a mathematical problem (as of finding the greatest common divisor) in a finite number of steps.
Altitude
The elevation of a (moving) object above a reference surface, usually mean sea level.
Amplitude
In the context of this book, the maximum departure of a wave from its average value; it is a measure for the strength of an oscillatory movement. For instance, the louder a sound, the larger the amplitude of the sound wave.
Aperture
In optics, an aperture is an opening through which light is admitted; it determines how collimated the admitted rays are. For a conventional camera, the aperture is materialized by the diaphragm as part of the lens. In radar, the aperture is related to the antenna length.
Aspect
The geographical direction toward which a slope faces, measured in degrees from north, in a clockwise direction.
Atmosphere The Earth’s atmosphere is the gaseous envelope surrounding the Earth. The atmosphere is classified into several layers, but there are no discernible boundaries; it gradually becomes thinner. Three quarters of the atmosphere’s mass is within 11 km of the Earth’s surface. An altitude of 120 km marks the boundary where atmospheric effects become noticeable during re-entry from space. Atmospheric scattering The process of particles or gaseous molecules present in the atmosphere redirecting EM radiation from its original path. A well known example is Rayleigh scattering. Atmospheric window A spectrum portion outside the main absorption bands of the atmospheric gases that can be used for remote sensing. Attribute
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Data associated with a spatial feature or sample location, stored as a column in a database table. The name of the column should suggest what the values in that column stand for. These values are known as attribute values.