GIS Dictionary | Letter A

– A –

The closeness or nearness of the measurements to the true or actual value of the quantity being measured. Usually represented as a percentile.

The cooling of air as it rises over the terrain. Conversely, the warming of air as it descends.

A set of characters containing either letters or numbers. For example, an alphanumeric password could be “2xbe14y”.

Acronym for American Standard Code for Information Interchange. ASCII is a code for representing English characters as numbers, with each character assigned a number from 0-127. An ASCII file is a text file in which each byte represents one character according to the ASCII code. ASCII files are sometimes called plain text files.

Direction that a surface faces.

An atlas is a collection of maps, usually bound into book form. As well as geographic features and political boundaries, many often feature geopolitical, social, religious and economic statistics. The name “atlas” derives from the custom of adorning the cover or title page of such collections with a picture of the Atlas of Greek mythology holding the Earth on his shoulders.This usage of the term dates from Gerardus Mercator’s Atlas Sive Cosmographicae, (Atlas, or Description of the Universe) of 1585-1595. The earliest atlas was Ptolemy’s Geography of c. 150 AD.

Information about a spatial feature. For example, attributes about a school may be the name, level of education, and number of students.

An expression of distance, measure in degrees.

GIS Acronyms

ACSM – American Congress on Surveying and Mapping

ASCII – American Standard Code for Information Interchange

ASPRS – American Society for Photogrammetry and Remote Sensing

Regional Organizations


AGRC – Utah Automated Geographic Reference Center

More geographic concepts from the GIS dictionary:

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

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