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DC GIS Glossary

For more information or for terms not defined here, please visit the ESRI GIS Dictionary.

Address Alias
A place name which is associated with an address. Address Aliases include buildings names, historical monuments, educational facilities, and more.

Address Anomaly
An address whose location is illogical. The address does not follow the standard rules of Washington, DC's addressing grid system. Types of address anomalies include, but are not limited to: wrong block, out of sequence, wrong side of street. Read the MAR Address Anomalies Report for full details.

Address Point
A map point over the location of an address. Multiple address points may exist within a lot.

Administrative and Other Boundaries
Manmade legal boundary descriptions for the purpose of governance and management.

Advisory Neighborhood Commissions (ANC)
Bodies of local government in Washington DC. There are 37 ANCs. They consider a wide range of policies and programs affecting neighborhoods, including traffic, parking, recreation, street improvements, liquor licenses, zoning, economic development, police protection, sanitation and trash collection, and the District's annual budget. The ANCs are the body of government with the closest official ties to the people in a neighborhood.

Aerial Photography
The taking of photographs from the air with a camera mounted on an aircraft.

Air Rights Lots
Air right lots are established by real property tax administration to reflect a party's right to construct an improvement above an existing area of land that is not owned by the constructor.

Land set aside at the time of the original founding and platting of the city for use by the US Federal Government. There are only 17.

The necessary GIS layers properly symbolized to create a common looking digital map of the District of Columbia.

Business and Economic Development
Economic activities or employment. For example, resources describing labor, revenue, commerce, industry, and specialized incentive areas.

The server system that allows District employees to use applications such as ArcGIS and Pictometry software via the Intranet.

Cultural and Society
The characteristics of societies and cultures. For example, resources describing natural settlements, anthropology, archaeology, traditional beliefs, manners and customs, and religion.

Detailed Metadata
This metadata satisfies the requirements of the Federal Geographic Data Committee (FGDC), as augmented by additional elements defined by ESRI. It is provided for all datasets with a Status of Available.

Refers to all the hardware, software, and databases that provide the central GIS functionality for the District of Columbia government.

A shortened term for 'population characteristics'. Demographics include race, age, income, mobility (in terms of travel time to work or number of vehicles available), educational attainment, home ownership, employment status, and even location. Distributions of values within a demographic variable, and across households, are both of interest, as well as trends over time.

Formal education information. For example, schools, universities, colleges, and related activities.

Height above or below sea level. For example, resources describing altitude, bathymetry, digital elevation models, slope, and products derived from this information.

Environmental resources, protection, and conservation. For example, resources describing pollution, waste storage and treatment, environmental impact assessment, water features, and drainage systems.

Facility and Structure
Manmade construction. For example, resources describing buildings, fences, and related items.

Feature Class
A collection of geographic features with the same geometry type (such as point, line or polygon), the same attributes, and the same spatial reference.

  • Point - a geometric element defined by a pair of x,y coordinates
  • Poly Line - a shape defined by a series of connected line segments
  • Polygon - a closed shape defined by a connected sequence of x,y coordinate pairs, where the first and last coordinate pair are the same and all other pairs are unique

Field Research
The gathering and research of information at the physical location; as opposed to research or information gathering in the office.

A geographical dictionary, an important reference for information about places and place-names and associated spatial location

The process of assigning geographic identifiers (e.g., codes or geographic coordinates expressed as latitude-longitude) to map features and other data records, such as street addresses.

Geographic Information System, a system for capturing, storing, analyzing, and managing data and associated attributes which are spatially referenced to the earth. In the strictest sense, it is a computer system capable of integrating, storing, editing, analyzing, sharing, and displaying geographically-referenced information. In a more generic sense, GIS is a tool that allows users to create interactive queries (user-created searches), analyze the spatial information, edit data, and present the results of all these operations.

Health services, human ecology, and safety. For example, resources describing human disease and illness, factors affecting health, hygiene, mental and physical health, substance abuse, and health services.

Significant features from the past. For example, resources describing landmarks, historical plans, settlements, and heritage.

Common examples of images used in GIS include remotely sensed data (for example, satellite data), scanned data, and photographs.

Laser Imaging Detection and Ranging, an optical remote sensing technology which measures properties of scattered light to find range and/or other information of a distant target. The prevalent method to determine distance to an object or surface is to use laser pulses. Like the similar radar technology, which uses radio waves instead of light, the range to an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal.

Positional information and services. For example, resources describing addresses, geodetic networks, postal zones and services, control points, and place names.

Master Address Repository. See the MAR Page.

Information that describes the content, quality, condition, origin, and other characteristics of data or other pieces of information. The DC Federated Data Model provides the District government standards for metadata.

Mobile Video
The product name of van-captured photographic elevations for buildings in the District of Columbia. The primary purpose of the project was for taxation and it was used in the creation of the MAR.

Data from all categories that cover the entire continental United States of America.

Neighborhood Clusters
There are 39 Neighborhood Clusters currently used for community planning and related purposes in the District of Columbia.

Refers to the central GIS staff, and not the DC GIS system.

The acronym for the agency that is the original source of the data. The source for nearly all map layers created by OCTO that are not part of the planimetric map is another District Agency.

Owner Point
A map point over a single lot, attributed with information about the owner.

Owner Polygon
A single polygon feature class that represents land with taxable information about the owner, taxes, land use, etc.

Parcel Lot
Land often not residing within a square, most of which were created in 1905 by Act of Congress. All the unsubdivided land from Washington County merged with the city of Washington to form the District of Columbia.

Shows high resolution images taken at oblique angles of about 45 degrees from the four compass points and from directly above.

Planimetric Map
Contains point and line map layers of visible features from aerial photography, such as streets, sidewalks, alleys, buildings, open space, utilities, etc.

Planning, Land Use, and Zoning
For example, resources describing zoning maps, and information used for planning the environment.

Police District
Police jurisdictions. See also Police Service Areas (PSA).

Police Service Area (PSA)
Every resident lives in a Police Service Area, and every PSA has a team of police officers and officials assigned to it. Learn more about PSA team members, and how to work with them to fight crime and disorder in neighborhoods, by visiting the MPDC website.

Voting boundaries established by the DC Board of Elections and Ethics.

Property and Land
For example, resources describing cadastral surveys and land ownership.

Public Safety
Resources related to emergency services. For example, Fire, EMS, and Police.

Public Services
Resources related to social and governmental services provided to the public.

The District of Columbia is divided into four quadrants: Northwest, Northeast, Southwest and Southeast.

Record Lot
Defined by the DC Surveyor. These are official, platted, recorded subdivision lots created by the DC Surveyor's Office in compliance with the Subdivision Ordinance of the District of Columbia. These typically must have public street frontage.

Lands acquired for use by the Federal Government after the original founding of the city. There are presently more than 750 US Reservations in DC. These were acquired by the Federal Government through purchase, condemnation, dedication or gift. The majority of US Reservations in Washington are under the jurisdiction of the National Park Service.

Lands acquired for use by the Federal Government after the original founding of the city. There are presently more than 750 US Reservations in DC. These were acquired by the Federal Government through purchase, condemnation, dedication or gift. The majority of US Reservations in Washington are under the jurisdiction of the National Park Service.

Single Member District (SMD)
Single Member Districts are boundaries, within ANCs, developed by the DC City Council. Each SMD has approximately 2,000 residents represented by a commissioner that is elected to the Advisory Neighborhood Commission.

A unit of land defined by the DC Surveyor that normally consists of a single city block and contains record and tax lots.

Street Spatial Database, the DDOT central GIS data repository for all transportation related assets and data.

Square, Suffix, and Lot. The identifier is used by the District of Columbia to uniquely locate property primarily for the purpose of taxation.

Indicates the stage of development of a dataset.

  • Available - The dataset is available in the Data Catalogue for distribution internally and externally.•Development - OCTO is developing and processing the data to prepare for its active use; it is not available for distribution.
  • QA/QC - OCTO is performing quality control processes on the dataset to assess quality, completeness, and utility; it is not available for distribution.
  • Restricted - The data is available for District government use only.
  • Improvement - Assessed through QC procedures, the dataset needs improvement via various data development activities; it is not available for distribution.
  • Acquisition - OCTO is seeking to obtain the dataset form the source or owner organization; it is not available for distribution.
  • Future - The dataset is designated for future development; it is not available for distribution.

Street Name Alias
An alternative or abbreviated name for a street. Examples of this include MISS for Mississippi or MLK for Martin Luther King Jr.

Summary Metadata
This is a shorter set of metadata to provide the basic information about a dataset. If a dataset does not have an Available status, not all of these data fields will be completed.

Tabular Data
Descriptive data stored in rows and columns in a database that can be linked to spatial data.

Tax Lot
A unit of land assigned by the real property tax administration that usually resides within a square. Often referred to as A&T lots or simply tax lots. These lots are strictly for real estate taxation purposes.

The means and aids for conveying people and goods. For example, resources describing roads, airports and airstrips, shipping routes, tunnels, railways and related assets.

Utility and Communication
Energy, water and waste systems, and communications infrastructure and services. For example, resources describing sources of energy, water purification and distribution, sewage collection and disposal, electricity and gas distribution, data communication, telecommunication, radio, and communication networks.

Vector Property Map. It is the product of the digital Coordinate Geometry entered property lines for the District of Columbia.

The District of Columbia is divided into eight. Visit the DC Council website for information on each ward.