GLOSSARY OF GEOSPATIAL AND GIS TERMINOLOGY
Last Updated 4/5/2010 (PDF)
Preamble: This listing of geospatial terms was developed at the direction of the MetroGIS Policy Board to help its members better understand recommendations they are asked to consider. The Policy Board adopted the initial version of this glossary on April 21, 2010.
This listing is intended to be a starting place. As the need is recognized, additions and modifications are to be incorporated. Users are encouraged to offer such modifications as they recognize the need.
Proprietary Terms/Products are followed by “ ** “. It is understood that the listing of these terms is incomplete.
Geospatial And GIS Terminology
ArcGIS**: A collection of software products developed by ESRI. This includes ArcView, ArcEditor, and ArcInfo levels of functionality as well as the main applications of ArcMap, ArcCatalog, and ArcToolbox.
Annotation: Descriptive text used to label geographic features on a map. This text is used for display rather than analysis.
Application: A program (software) or web mapping service designed to perform a specific task. Examples include word processing software, database programs, and mapping tools.
GIS applications can be used to solve problems, automate tasks, and generate information within a specific field of interest. They can also be used to search, analyze, and map data to answer particular questions.
Arc: 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 called nodes.
Attribute: Descriptive information about a geographic feature or location that is usually stored in a table. Examples include ownership of a parcel of land, the population of a neighborhood, or the speed limit or name of a road.
Basemap: A map containing geographic features used for locational reference. Roads are commonly found on basemaps.
Best Practice or Best Management Practice: A recognized technique, method, or process related to developing, documenting, managing, sharing, distributing, or utilizing geographic data or applications which promotes consistency and compatibility of the data. It is a reflection of what the GIS community has found to work most efficiently and effectively. Best practices or guidelines may evolve into standards when officially adopted and mandated.
Broker: A searchable catalog or directory of datasets and services that provide information about resource availability and accessibility. This is similar to conducting a Google search, then following a link to the information of interest.
The broker function facilitates enforcement of requisite standards and protocols, as well as possibly providing authentication (security) services. Examples include the Federal Geographic Data Committee (FGDC) Clearinghouse and Geospatial One-Stop (Geodata.gov) sites. The Clearinghouse provides a single point of contact regarding available resources while at the same time tracking data accessibility. Geodata.gov provides access to maps, data and other geospatial services.
Buffer: A zone of a specified distance around coverage features, useful for proximity analysis.
Business Information Need: Data needed to accomplish a business task. For example, needing to know the owner of a parcel of property in order to contact them, needing to know which community a particular property is located, or finding the drainage outlet for a particular wetland.
Cadastre: An official record of dimensions, land value, and ownership used to calculate taxes.
Cadastral Survey: A boundary survey taken for the purposes of ownership and taxation.
Cartography: The art and science of making maps.
Catalog: A collection of data or metadata that is searchable and often organized by category, to assist the discovery and retrieval of datasets or services.
Catalog Entry: An item in the list of contents of a catalog that is searchable by keyword or category for example.
Clearinghouse: A central institution or agency for the collection, maintenance, and distribution of information, metadata, and data. A clearinghouse provides widespread access to information and is generally thought of as reaching or existing outside organizational boundaries.
Clip: The spatial extraction of those features from one map layer that reside entirely within a boundary defined by features in another map layer, much like a cookie cutter.
Coordinate: A set of numbers (x, y values) that designate location in a given reference system (coordinate system). Coordinates represent locations on the Earth’s surface relative to other locations.
Consensus: General agreement or accord about a particular decision. This is the preferred means of decision-making by MetroGIS.
DataFinder: A one-stop-shop for finding geospatial data pertaining to the seven county Twin Cities metropolitan area. Its primary function is to facilitate sharing of GIS data among organizations and provides metadata describing GIS datasets, which can be directly downloaded or used via web services.
DataFinder Café: An interactive tool for viewing and downloading GIS datasets. It allows users to download datasets by user defined geographic extents or selections. The Café also allows users to browse GIS datasets, print maps, and save mapping sessions for later use or for sharing with others.
Data Standard: An approved model of what data should be recorded, how data should be recorded, and how data should be supported by a system in order to retain its full meaning.
A standard should be a well defined set of properties or specifications for measuring acceptability, quality, and accuracy for a specific type of data which is accepted as correct by custom, consent, or authority that facilitates the creation, use, or dissemination of such data.
Dataset: A collection of related data, which is grouped or stored together.
Datum: The reference location from which measurements of the Earth are made. A datum defines the size and shape of the Earth and the origin and orientation of the coordinate systems used to map the Earth. Knowing the datum is important because referencing the wrong datum can result in significant error.
Endorsed Regional Solution: Specifications for geospatial data that benefit the user community which have been approved by a regional entity such as MetroGIS. The endorsement of a regional dataset involves guidelines for access, content, and distribution in order to provide a consistent dataset across the region’s jurisdictions.
Field: In a database, another term for column.
Geocoding: A GIS process for converting street addresses, intersections or named locations into spatial data that can be displayed or mapped. For example, the geographic location for an address may be found by comparing it to reference data, such as address points, street centerlines or zip code boundaries. Reverse geocoding is the opposite, for example finding attribute information from a point on a map.
Geocoding Service (Address Locator): A service that allows the user to geocode non-spatial data using a web or desktop application.
Geographic Data (Geospatial Data): Data having two components: spatial and attribute. The spatial component is the location of the feature data in map coordinates. The attribute component is the data that describes the feature.
Examples of spatial data:
- point: fire hydrant
- line: street
- polygon: parcel boundary
- raster: aerial photography or shaded relief
Examples of attributes data:
- fire hydrant: diameter of pipe
- street: street name
- parcel: property owner name
- shaded relief: elevation
Geographic Information System (GIS): An organized collection of computer hardware, software, geographic data, and personnel designed to collect, store, update, manipulate, analyze and display geographic information. GIS is the merging of database technology and cartography.
Georeferencing: A process for aligning geographic data to a known coordinate system so it can be used with other geographic data. Georeferencing may involve shifting, rotating, scaling, and rubber sheeting (stretching) the data or image. This method is not as precise as orthorecitification.
Geospatial Web (GeoWeb): A relatively new term that reflects a blending of geographic (location-based) information with information from the Internet. This has created an environment where searches can be based on location as well as keywords.
The GeoWeb is currently characterized by geo-browsers such as Google Earth, Google Maps, Bing Maps, and Yahoo Maps.
Global Positioning System (GPS): A system of global navigation satellites used for determining location on the earth. A GPS can be very accurate, making it a useful tool for surveying and GIS as well as navigation.
Hydrography: The measurement and description of water bodies.
Infrastructure: The system of human-made physical structures that provide communication, transportation, utilities and other public services including hospitals, police and fire stations. This information is often included within a core set of GIS data. Also refers to the collection of computers, servers, other related hardware and connecting cables that allow a group of computer users to communicate and share information.
Interoperability: The capability of components or systems to exchange data with other components or systems, or to perform in multiple environments. For example, interoperability is required for a GIS user using software from one vendor to study data compiled with GIS software from a different provider.
Layer: A thematic set of spatial data, layers are organized by subject matter.
Legend: The reference area on a map that lists and explains the colors, symbols, line patterns, shadings and annotations used on the map; the symbol key to interpret the map.
Light Detection and Ranging (LIDAR): An optical remote sensing technique that uses laser pulses to determine elevation with high accuracy.
Line: A set of ordered coordinate pairs that represent a linear feature with no area, or with a shape too narrow to be displayed as a polygon.
Map: A graphic representation of geospatial data. A map displays data.
Map Projection: A mathematical model that transforms the locations of features on the Earth’s surface (sphere) to locations on a two-dimensional surface (flat map).
Mashup: A mixture or combination of content, elements, or scripts from multiple sources or websites. For example, one could add schools information from the Department of Education and public transportation routes from MetroGIS to a Google Map.
Metadata: Information that describes the content, quality, condition, origin, and other characteristics of data. Metadata answers questions about how, when and where the data was collected. It can also provide information about origin, source, reliability and accuracy.
MetroGIS: A geospatial collaborative organization serving the Twin Cities metropolitan area. Its primary functions focus on: a) the development and implementation of a collaborative regional solution for sharing information needs (e.g., geospatial data, related applications, standards and best practices), b) widespread sharing of geospatial data via DataFinder.org website, c) the value of GIS technology as a core business tool, and d) sharing knowledge relevant to the advancement of GIS technology. Beneficiaries of these efforts include local and regional governments, as well as, state and federal government, academic institutions, nonprofit organizations and business interests.
Distinguishing Characteristics include:
- Unincorporated organization -no mandate or legal standing
- Cannot own data, receive, or spend funds-rely on stakeholders
- Elected officials comprise the Policy Board
- Consensus-based decisions on matters fundamental to success
- Voluntary compliance for endorsed policies/procedures
- Forum to foster collaboration on a breadth of shared geospatial program needs - more than just data.
Metropolitan Area: The seven county service area of the Metropolitan Council. Governments within Anoka, Carver, Dakota, Hennepin, Ramsey, Scott and Washington Counties are represented on the MetroGIS Policy Board.
Metropolitan Council: A 17-member council that serves as a regional planning organization for the seven-county Twin Cities metropolitan area.
The council runs the regional bus and light rail system, collects and treats wastewater, manages regional water resources, plans regional parks, and administers funds that provide housing opportunities for low and moderate income individuals and families.
Minnesota Geospatial Information Office (MnGeo): Established in May 2009, this is the first state agency in Minnesota with legislatively defined responsibility for coordinating GIS within Minnesota. The organizational structure includes two advisory committees that make recommendations to the Chief Geospatial Information Officer (CGIO). These committees include a statewide geospatial advisory council and a state agency advisory council.
MrSID**: MrSID is a compression format applied to raster data, most commonly aerial photos.
National Spatial Data Infrastructure (NSDI): The technologies, policies and people necessary to promote sharing of geospatial data throughout all levels of government, the private and non-profit sectors, and the academic community. The goal is to reduce duplication of effort among agencies, improve quality and reduce costs related to geographic information, to make geographic data more accessible to the public, to increase the benefits of using available data, and to establish key partnerships with states, counties, cities, tribal nations, academia and the private sector to increase data availability.
Open Geospatial Consortium (OGC): The OGC is a non-profit, international, voluntary consensus standards organization that is leading the development of standards for geospatial and location based services.
Open Source Data Model: A standard that has members of the GIS user communities cooperatively working to correct and improve spatial data and attributes in exchange for less restrictive uses of the data.
Open Source Software: A program in which the source code is available to the user for their use and/or modification from its original design free of charge. Open source code is typically created as a collaborative effort in which programmers improve upon the code and share the changes within the community. The result of this collaboration is the fast and affordable development of high quality technologies and software products.
Orthophotography (Orthoimagery): An aerial photograph geometrically corrected so that the scale is uniform and distortion is corrected to remove camera tilt and/or ground relief. This is similar to georeferencing an aerial photo, but much more accurate.
Peer Review Forums: A facilitated event at which users of a particular regional solution are invited to share ideas on how to improve the solution, including but not limited to data content, access and custodial responsibilities.
Through these events, MetroGIS identifies ways to ensure that solutions maintain their relevance with changing user needs, and leverage resources that were not available when the solution was implemented.
Point: A single x, y coordinate point that represents a geographic feature.
Polygon: A representation of an area defined by lines that make up its boundary. For example, it may represent a building footprint, parcel, city limits, or country’s boundary.
Projection: A mathematical model that transforms the locations of features on the Earth’s surface (sphere) to locations on a two-dimensional surface (flat map).
Raster: A way of representing geographic features by dividing the world into discrete squares called cells. Aerial photos are a common example of raster data.
Remote Sensing: The process of acquiring information about an object without contacting it physically. Methods include aerial photography, radar, and satellite imaging.
Service Broker: A searchable catalog or directory of services that provides information about resource availability and accessibility.
Services: Reusable, self-contained collections of executable software components. They are software that can work in different operating systems, networks and application frameworks. They are basic to creating highly integrated and distributed application systems. GIS data is often provided via a web service. Spatial data served out by one organization via a web service can be consumed by GIS users with access to the web and the software to consume the service.
Shapefile: A shapefile is a dataset that is associated with ESRI’s GIS software products. Shapefiles contain spatial geometry (points, lines, polygons) in multiple files.
Shared Business Information Need: Information needed to carry out the business of more than one organization.
SOAP: Is an acronym for SIMPLE OBJECT ACCESS PROTOCOL which is a XML (defined below) based protocol developed for exchanging information between peers in a decentralized, diverse environment. SOAP allows programs on different computers to communicate regardless of operating system or platform; it is used in Web Services.
Spatial Data (Geospatial Data): Information about the locations and shapes of geographic features, which are often stored as coordinates and topology, data that can be mapped.
Spatial Data Infrastructure (SDI): A framework that facilitates access to geographic information using a minimum set of standard practices, protocols, and specifications.
Stakeholder: A person, group or organization with an existing or potential interest in MetroGIS. This includes both users of its services and contributors.
Succession Planning: Strategies to accomplish successful transitions in leadership roles critical to an organization’s long term success (e.g., committees, staff support, and advocates within critical stakeholder organizations).
Topology: The spatial relationship between geographic objects. For example, topological information for a city boundary would include the names of adjacent cities.
Vector: A coordinate based data structure commonly used to representing geographic features as an ordered list of vertices.
“View only” Access: Data is displayed as a map, graphic or summary table. A user may print or save the displayed information, but cannot download or edit the data.
Web Coverage Service (WCS): An interface standard of the Open Geospatial Consortium (OGC) that provides geographical coverages (e.g. aerial photography, land cover data, digital elevation models) across the web using platform independent calls. The coverages are provided as objects that can be spatially analyzed by the end user.
Web Services: GIS Web Services are self-contained application components that can be published or accessed over the World Wide Web. Each performs a specific GIS function as part of a larger web site, portal or business application.
Web Feature Service (WFS): A Web Service that allows a user to request, create, update, delete and/or save geospatial data as if it were on the user’s own computer or network.
Web Mapping Service (WMS): A Web Service that permits a user to request and obtain a map image, which can be viewed on its own or with other geospatial data. The image created by the WMS cannot be edited but it can be combined with other WMS data as well as locally stored data. A WMS is a virtual copy of the geospatial data, meaning that when the user’s computer is shut off, the map image is no longer available.
WIKI: A website that allows the creation and editing of any number of interlinked web pages through a web browser. They are often used in an ongoing process of creation and collaboration that promotes meaningful discussion and teamwork across the web.
XML (eXtensible Markup Language): A standardized general purpose language for designing text formats that allows the interchange of data between computer applications. XML is designed for creating web documents such as the production of GIS metadata.
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