THE MARYLAND-NATIONAL CAPITAL PARK AND PLANNING COMMISSION
PG Planning
Glossary of Planning and Geographic Information Systems (GIS) Terms

Glossary is usually defined as an alphabetical list of technical terms in some specialized field of knowledge. This knowledge base glossary provides a collection of knowledge base documents that define many technical terms. These terms are arranged alphabetically, but you can quickly jump to a specific term by selecting its first letter from the index of the knowledge base glossary below.

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Access Right
The privileges accorded a user for reading, writing, deleting, updating and executing files on a disk. Access rights are stated as 'no access', 'read only' and 'read/write'.
Accessory Use
The use of a building, structure or land that is subordinate to, customarily incidental to, and ordinarily found in association with, a principal use, which it serves. (See Section 27-107.01 of the Zoning Ordinance)
Acre
43,560 square feet. (about the size of a football field)
Activity Center
A community focal point providing for the combination, rather than scatteration, of general retail, service commercial, professional office, higher density housing, and appropriate public/quasi-public uses. (See also VILLAGE ACTIVITY CENTER, COMMUNITY ACTIVITY CENTER, AND MAJOR COMMUNITY ACTIVITY CENTER)
See also:  Village Activity Center, Community Activity Center, Major Community Activity Center
Address Matching
A mechanism for relating two files using address as the relate item. Geographic coordinates and attributes can be transferred from one address to the other. For example, a data file containing student addresses can be matched to a street coverage that contains addresses creating a point coverage of where the students live.
Adequate Public Facilities (Apf) Ordinance
The ordinance requiring a determination of the adequacy of public facilities to accommodate growth resulting from approval of a subdivision application.
Afforestation
The establishment of a tree cover on an area from which it has always or very long been absent, or the planting of open areas that are not presently in forest cover. (See also REFORESTATION)
See also:  Reforestation
Agricultural Assessment
A state program in which land used for agricultural purposes is assessed based on its value as agricultural land as opposed to a higher valuation.
Air Installation Compatible Use Zone (Aicuz) Study
An extensive analysis of the effects of noise, aircraft accident potential, and land use and development upon present and future neighbors of Andrews Air Force Base.
Air Rights
The development rights of the space above a piece of land and its existing ground level use.
Allocation
The process of assigning arcs in a network to the closest center until the maximum impedance or resource capacity of the center is reached.
Ancillary
Certain small shops, stores, restaurants associated with larger uses, e.g., office and residential, that supply necessities in frequent demand and the daily needs of an area, with a minimum of consumer travel (e.g., restaurants, dry cleaners in an office or mid-rise residential building).
Annotation
1. Descriptive text used to label coverage features. It is used for display, not for analysis. 2. One of the feature classes in a coverage used to label other features. Information stored for annotation includes a text string, the location at which it is displayed, and a text symbol (color, font, size, etc.) for display.
Arc
1. An ordered string of vertices (x,y coordinate pairs) that begin at one location and end at another. Connecting the arc's vertices creates a line. The vertices at each endpoint of an arc are called nodes. 2. A coverage feature class used to represent linear features and polygon boundaries. One line feature can contain many arcs. Arcs are topologically linked to nodes (arc-node topology) and to polygons (polygon-arc topology). The descriptive attributes of arcs are stored in the arc attribute table (AAT).
Area Master Plan Or Area Plan
Area Master Plans: Area master plans consist of a plan map along with supporting data, text and other maps. They provide specific recommendations on a planning area or subregion basis on the environment, historic preservation, living areas, housing, commercial areas, employment areas, urban design, circulation, and transportation.(See also MASTER PLAN.)
See also:  Master Plan
Arterial
A highway, usually within a 120-foot right-of-way, for through traffic with access controlled to minimize direct connections, usually divided and on a continuous route.
At-Grade
Level for a road, building or other structure at the same grade or level as the adjoining property (as opposed to a depressed or elevated road, building or other facility).
Attribute
1. A characteristic of a geographic feature described by numbers, characters, images and CAD drawings, typically stored in tabular format and linked to the feature by a user-assigned identifier (e.g., the attributes of a well might include depth and gallons per minute). 2. A column in a database table. See also item.
Attribute Table
An INFO or other tabular file containing rows and columns. In ArcInfo, attribute tables are associated with a class of geographic features, such as wells or roads. Each row represents a geographic feature. Each column represents one attribute of a feature, with the same column representing the same attribute in each row.
Average Daily Traffic (Adt)
The average number of vehicles passing a specified point on a highway during a 24-hour period.