Glossary

This section describes the basic terminology and concepts used in the ALG software package.

TermDescription

Atmospheric Transfer Functions

Spectrally-dependent variables that define the light scattering and absorption processes within a planetary atmosphere as function of key input atmospheric variables, illumination conditions and observation geometry. Read more...

Data type

Attribute for RTM input variables that defines the system-independent types of values: INTEGER, FLOAT, STRING.

Look-Up Table (LUT)

Array that replaces runtime computation through access and interpolation of its stored values. LUTs are defined by their grid points (also called "nodes") and output variables. A LUT grid point is a vector with the key input parameters/variables values that were input to run the computationally-expensive RTM. A LUT output variable is the generated output of process run at a given grid point.

LUT Configuration File

Data file containing the necessary input parameters and variables that defines the generation of an atmospheric LUT through the execution of an RTM.

Parameter type

Attribute for RTM input variables that defines whether the variable is discrete (i.e., only admits a, typically INTEGER, value within a given discrete set) or continuous (i.e., admits any, typically FLOAT, value within a defined range).

Radiative Transfer Model (RTM)

Computer implementation of the numerical solution of a radiative transfer equation..

Software Configuration File

Data file containing the software configuration parameters necessary to operate the ALG software package.

Spectral Band

Continuous range of wavelengths in which the output LUT variables are defined (e.g., 500-780 nm). LUT output variables can be composed of one or more (non-contiguous) spectral bands.
Do not confuse with spectral channel.

Spectral Channel

Acquisition of a given wavelength range by a remote sensing instrument and defined by its wavelength barycentre and FWHM width (e.g., Sentinel-3/OLCI channel #1 is centred at 400 nm and has a FWHM width of 15 nm).
Do not confuse with spectral band.

Static

Attribute for RTM input variables that defines whether the variable can vary its value (dynamic) or is fixed (static) within an atmospheric LUT.

Visibility

Attribute for RTM input variables that control the access of a variable to Basic, Medium or Advanced users