Glossary
Earthworks: Terrain surrounded by (interrupted or continuous) ditches, palisades, and embankments
Echo width (LiDAR): The duration (or width) of the reflected signal, or “echo”, that returns to the sensor after bouncing off an object. This width provides information about the nature and structure of the surface: a narrow echo width indicates a sharp, well-defined object, while a broader echo may suggest a more diffuse or complex surface, such as a canopy.
Echosounder: Active sensor which emits acoustic waves into the water column and records the time interval between the emission and return of the pulses. The sensor is used to map the waterbed and detects objects underwater.
Echogram: Graphical representation of the sonar data collected as acoustic signals are transmitted and reflected off the seafloor and underwater objects.
Electrical Resistivity Survey: Geophysical sensor technique that measures the electrical resistance of the soil to map subsurface structures or layers.
Electromagnetic spectrum: The full range of electromagnetic radiation present in the universe subdivided into several spectral bands according to their frequency and wavelength. The electromagnetic bands are (from low to high frequency): radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
Electromagnetic radiation: Energy travelling through space at the speed of light as both synchronized waves of the electric and magnetic field without mass, and as particles of light.
Electromagnetic Induction (EMI): A geophysical sensor technique used to measure subsurface variations in electrical conductivity. This is achieved by inducing electrical currents in conductive materials in the ground, which generate secondary magnetic fields that are detected by the receiver.