Science and Development Network
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Definitions
Below is a directory of terms used in discussions about remote sensing for natural disasters. Most of the terms have been reproduced from the Canada Centre for Remote Sensing and the UN Department of Humanitarian Affairs.
New technologies have the potential to accelerate a country's development, but a global technology gap remains.
A
Aftershock
A small earthquake that follows the main shock and originates close to its focus. Aftershocks generally decrease in number and magnitude over time.
Avalanche
The rapid and sudden sliding and flow of masses of mixtures of snow, ice and rock material.
B
Band
A selection of wavelengths.
C
Crop failure
Abnormal decrease in crop yield such that it is insufficient to meet the community's nutritional or economic needs.
D
Damage assessment
Evaluation and recording of damage to structures, facilities, or objects.
G
Geographical information systems (GIS)
A computer-based system designed to input, store, manipulate, and output geographically referenced data.
H
Hazard
A threatening event, or the probability of occurrence of a potentially damaging phenomenon within a given time period and area.
I
Interferometry
The combination of two radar measurements of the same point on the ground, taken at the same time, but from slightly different angles, to produce stereo images. Using trigonometry to calculate the distance between the radar and the Earth's surface, these measurements can produce very accurate height maps, or maps of height changes used to assess earthquake damage, volcanic activity, and landslide or glacier movement.
M
Microwave band
The portion of the electromagnetic spectrum lying between the far infrared and the conventional radio frequency portion. While not bounded by definition, it is commonly regarded as extending from 1 mm to 1 m in wavelength (300 GHz to 0.3 GHz frequency).
P
Polar orbit
An orbit in which a satellite passes above or nearly above both poles of the Earth in each revolution. It has an inclination of (or very close to) 90 degrees to the equator. A satellite in a polar orbit will usually pass over the equator at a different longitude on each revolution. A polar orbit has an altitude of approximately 1000 kilometres above the ground.
R
Radio Detection and Ranging (RADAR)
A method, system or technique for using beamed, reflected, and timed electromagnetic radiation to detect or track objects and measure altitude and terrain.
Radiometer
An instrument for quantitatively measuring the intensity of electromagnetic radiation in some band of wavelengths in any part of the electromagnetic spectrum.
Recovery
The coordinated process of supporting disaster affected communities in reconstructing physical infrastructure and restoring social, economic and physical well-being.
Rehabilitation
The operations and decisions taken after a disaster with a view to restoring a stricken community to its former living conditions, whilst encouraging and facilitating the necessary adjustments to the changes caused by the disaster.
S
Spatial data
Data that refer to a location (which may be a specific location on the Earth's surface, or relative to an arbitrary point).
T
Thematic Mapper
A high-resolution scanner system on board the Landsat-4 and Landsat-5 satellites. Landsat 7 carries the ETM or Enhanced Thematic Mapper sensor.
Thermal band
A general term for middle-infrared wavelengths which are transmitted through the atmosphere window at 8–13 micrometers. Occasionally also used for the windows around 3–6 micrometers.
Tsunami
A series of large waves generated by sudden displacement of seawater (caused by earthquakes, volcanic eruptions or submarine landslides) and capable of travelling over large distances and causing a destructive surge on reaching land.
V
Visible band
The part of the electromagnetic spectrum that can be perceived by the naked eye. This band ranges from 7500 ang. to 4000 ang.
Volcano
The mountain formed by local accumulation of volcanic materials around an erupting vent.
Vulnerability
Degree of loss (measured as a percentage) resulting from a potentially damaging phenomenon.
W
Warning
Dissemination of messages signalling imminent hazards which may include advice on protective measures.
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