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Glossary of Terms

Access Area - The area around each cell-site where phone calls are directed.

Analog - A system of cellular phone signal transmission based on the sending of the modulating amplitude of the communication signal.

Avenue - A scripting language used in ArcView GIS software.

Cell-Site - A cellular phone transmission tower. (Also known as a cell-tower)

Cell-Splitting - The practice by which a cellular phone company replaces a single omnidirectional cellular transmitter with an array of directional cellular transmitters each pointed in different, opposing, directions.  Cell-splitting results in an increased capacity of a cell-site because one transmitter has been replaced by a whole array of transmitters.

Convergence Center - Areas (normally buildings) designated as community gathering places in the event of a natural disaster, such as an earthquake. Convergence centers commonly include schools, recreation centers, hospitals, etc.

Coverage/Theme - A map layer in a GIS database.

Digital PCS - See "PCS".

Digital Orthophotography -Digital photography that has been rectified by using known ground positions to remove distortions in the original photography that are a result of topographic effects and camera tilt.

Digitization - The process of transforming paper-based spatial information into digital information. In the context of this project, this mainly involves converting paper maps into digital coverages in a GIS. [Also see "Heads-up Digitization"]

Directional Antenna - An antenna, transmitter, or beacon which transmits its signal in a straight line.

Disaster Response Route - These are selected roadways intended to provide vital vehicle access in the event of a major disaster. The roads dedicated for this purpose are supposed to be kept clear for the emergency and official vehicles for the first stages of disaster recovery.

Flower Tower - A Lattice tower that narrows near the top.

GIS - A Geographic Information System. A spatially-referenced geographic database which allows for sophisticated analysis and queries.

Heads-up Digitization - A method of digitizing where a GIS operator uses one digital map or photograph on screen to digitize necessary features.

Lattice Tower - A cellular tower constructed with metal crossbeams supporting its three or four legs. Its fairly wide base and careful engineering result in a very stable structure that is able to withstand strong earthquakes.

Liquefaction - A phenomenon where the strength of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction has the potential of causing a considerable amount of damage to buildings which are constructed over unstable soils, such as those of the city of Richmond.

MMI - The Modified Mercalli Index (MMI), sometimes also called the Modified Mercalli Intensity scale, describes the damage and the intensity of an earthquake. A value of 1 stands for hardly any damage, while a value above 9 stands for considerable damage and destruction.

Monopole - A single, normally free-standing, vertical pole carrying cellular transmitters.

NHEMATIS - A software program created by Nobility Software that is used for the collection, representation and analysis of natural hazard information. The name of the software is an acronym for: Natural Hazards Electronic Map and Assessment Tools Information System.

Omnidirectional Antenna - An antenna, transmitter, or beacon which transmits its signal in a radial fashion in all directions around it.

PCS - A system of cellular phone signal transmission based on the sending of a binary-coded communication signal. Also known as "Digital PCS".

Reiteration - The process of going over a selected set of commands in a computer programming script repeatedly for a set number of times, or until a particular condition is met.

Saturated Cell-site - A cell-site that has reached the limit of users which are allowed to use it. A saturated cell-site will not allow any more cell-phone users to access it.

Subduction Zone - The region below the earth's crust where a tectonic plate slides under another. Subduction zones (such as the area near the Lower Mainland) are normally very earthquake-prone.

Thiessen Polygons - A method of creating polygons (or proximal regions) around point objects in a GIS by defining them mathematically, dividing the space between each point, and connecting these distances with lines.

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This site produced by the CELL-GIS Project Group   --   March 22, 2000
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