Glossary of Terms

Accuracy – The difference between a set of representative values and the actual values. The accuracy of a point location would be the difference between the point's coordinates in the Geographical Information System (GIS) and the coordinates accepted as existing in the real world.

ACSO – Accredited Community Safety Officers (ACSOs) have the power to request the name and address of offenders. Failure to comply makes them liable to arrest by a police officer. They also have the power to confiscate alcohol and cigarettes from young people who are under-age, can require the removal of abandoned vehicles, can take steps to enforce laws on fly tipping. Run and hosted by Hampshire County Council, the service is offered to the Counties Districts (excluding Southampton, Portsmouth and the Isle of Wight).

Address data – Data that contains address information used for geocoding. Address data may consist of one individual address or a table containing many addresses.

Aggregate data – Aggregate data present the total number of occurrences within a geographic area, not individual data.

Analysis – A systematic examination of a problem or complex entity in order to provide new information from what is already known.

Attribute data – Data that relate to a specific, precisely defined location. The data are often statistical but may be text, images or multi-media. These are linked in the GIS to spatial data that define the location.

Base data – Map data over which other, thematic information is placed.

Binary – In computing, having only two states, such as yes or no, on or off, true or false, or 0 or 1.

Boundary – A line separating adjacent political entities, such as countries or districts; adjacent tracts of privately-owned land; or adjacent geographic zones, such as ecosystems.

Buffering – A buffer is a polygon that encloses all areas within a set distance of the spatial features. Points, lines and polygons can all have buffers placed around them. For example, if a user is interested in all areas within 1km of a church, a buffer would be placed around all the points representing churches. This would create a new layer consisting of polygons representing those areas within 1km of a church.

CADDIE – Acronym for Crime And Disorder Data Information Exchange.

Centroid – A point at the geometric centre of a polygon. This can be used to represent a polygon as a point.

Choropleth maps – Maps of quantitative data that show patterns by using different colours or different shading for polygons classed in some way. For example, a map of polygon-based crime rates (as actual counts per 1000 population) might divide rates anywhere between 0-100 and shade the polygons accordingly. see also Thematic Map.

Coordinate pair – An x and y coordinate used to represent a location in two-dimensional space.

Correlation – A form of statistical modelling that attempts to summarise how one dataset will vary in response to another.

Crime and Disorder Reduction Partnerships – see Crime and Disorder Reduction Partnerships

Data – Any collection of related facts arranged in a particular format; often, the basic elements of information that are produced, stored, or processed by a computer.

Data capture – The process by which data are taken from the real-world primary source, or from a secondary source such as a paper map, and entered into GIS software. For primary data this is usually through the use of Global Positioning Systems (GPS). For secondary data it is usually through digitising or scanning.

Data sharing – Making data available and accessible to organisations or individuals other than the creator of the data.

Database – One or more structured sets of data, managed and stored as a unit and generally associated with software to update and query the data.

Database Management Systems – Software systems specifically designed to store attribute data.

Dataset – Any collection of related data, usually grouped or stored together.

Digitising – The process of converting the geographic features on an analogue map into digital format.

Easting – The positive x-value in a rectangular coordinate system.

Ecological fallacy – The mistake of assuming that where relationships are found among aggregate data, these relationships will also be found among individuals or households.

Enterprise GIS – A geographic information system that is integrated through an entire organization so that a large number of users can manage, share, and use spatial data and related information to address a variety of needs, including data creation, modification, visualization, analysis, and dissemination.

Error – In the context of GIS this means the difference between the real world and its digital representation.

Feature – A representation of a real-world object on a map.

Gazetteer – Often used to standardise place names or to locate place names within a hierarchy.

Geocoding – A GIS operation for converting street addresses into spatial data that can be displayed as features on a map, usually by referencing address information from a street data layer.

Geographic data – Information describing the location and attributes of things, including their shapes and representation. Geographic data is the composite of spatial data and attribute data.

Geographical Data Anaslysis (GDA) – A way of analysing data that explicitly incorporates information about location as well about attribute. This term may be used almost interchangeably with spatial analysis.

Geographical Information Science – Methods of exploring and analysing spatially referenced data that take account of the benefits and limitations of such data.

GIS – Acronym for geographic information system. Computer software that combines database management system functionality with information about location. In this way it is able to capture, manage, integrate, analyse and display data that is spatially referenced to the earth's surface.

GIS data – Data stored in a GIS are represented in two ways: attribute data says what the feature is, and spatial data says where it is using points, lines, polygons, or pixels.

GPS – Acronym for Global Positioning System. A system based on satellites that allows a user with a receiver to determine precise coordinates for their location on the earth's surface. These are a primary source of spatial data.

Granularity – The coarseness or resolution of data. Granularity describes the clarity and detail of data during its capture and visualization.

Graphic primitive – The basic representations of spatial features used in GIS. These are usually points, lines, polygons, or pixels.

Histogram – A graph showing the distribution of values in a set of data. Individual values are displayed along a horizontal axis, and the frequency of their occurrence is displayed along a vertical axis.

HTML – Acronym for Hypertext Mark-up Language. A mark-up language used to create Web pages for publication on the Internet. HTML is a system of tags that define the function of text, graphics, sound, and video within a document, and is now an Internet standard maintained by the World Wide Web Consortium.

HTTP – Acronym for Hypertext Transfer Protocol. The protocol maintained by the World Wide Web Consortium for communicating between servers and clients to exchange HTML documents across the Internet.

Intranet – A computer network, often using the same software and serving the same functions as those found on the Internet, that is restricted to users within an organization.

IP Address – Acronym for Internet protocol address. A unique number, such as 10.48.6.8, that identifies each computer on the Internet. IP addresses are similar to phone numbers, and allow data to travel between one computer and another via the Internet.

Layer(s) – GIS sub-divides features on the earth's surface according to a specific theme. Each theme is then georeferenced. Examples of layers for a study area might include: roads, railways, urban areas, coal mines, etc. A layer usually consists of both spatial and attribute data.

Legend – The description of the types of features included in a map, usually displayed in the map layout. Legends often use graphics of symbols or examples of features from the map with a written description of what each symbol or graphic represents.

Line – A spatial feature that is given a precise location that can be described by a series of coordinate pairs. In theory a line has length but no width.

Location – The position of a feature on the earth's surface. In GIS this is usually explicitly defined in terms of precise coordinates.

Metadata – Information that describes the content, quality, condition, origin, and other characteristics of data or other pieces of information. Metadata for spatial data may describe and document its subject matter; how, when, where, and by whom the data was collected; availability and distribution information; its projection, scale, resolution, and accuracy; and its reliability with regard to some standard.

Move map – see Pan

Northing – The positive y-value in a rectangular coordinate system.

Pan – To shift a map image relative to the display window without changing the viewing scale.

PDF – Acronym for Portable Document Format. A file format from that creates lightweight text-based, formatted files for distribution to a variety of operating systems.

Pixels – The small units that sub-divide space to make up a raster surface. They are usually small grid squares.

Points – Spatial features that are given a precise location that can be described by a single coordinate pair. In theory a point has neither length nor width.

Polygons – Spatial features that are areas or zones enclosed by precisely defined boundaries. The boundaries of a polygon are formed from one or more lines.

Qualitative data – Data which measure intangible data, such as peoples' attitudes and opinions.

Quantitative data – Data grouped or shown by measurements of number or amount, such as population per unit area.

Raster data – A way of representing the earth's surface by sub-dividing it into small pixels, usually square cells. Each pixel has values attached to it providing attribute data about the pixel.

Real time data – Data that is displayed immediately, as it is collected. Real-time data is often used for navigation or tracking.

Record – A set of related data fields, often a row in a database, containing all the attribute values for a single feature.

Server – A computer that manages shared resources, such as disks, printers, and databases, on a network.

Spatial analysis – A way of analysing data that explicitly incorporates information about location as well about attribute. This term may be used almost interchangeably with geographical data analysis.

Spatial data – Data that define a location. These are usually either points, lines, polygons or pixels.

Super Output Areas – A geographic hierarchy designed to improve the reporting of small area statistics in England and Wales. see: Neighbourhood Statistics

Symbol – A graphic used to represent a geographic feature or class of features. Symbols can look like what they represent (trees, railroads, houses), or they can be abstract shapes (points, lines, polygons) or characters. Symbols are usually explained in a map legend.

Table – A set of data elements arranged in rows and columns. Each row represents a single record. Each column represents a field of the record. Rows and columns intersect to form cells, which contain a specific value for one field in a record.

Temporal data – Data that explicitly refer to time.

Thematic Map – A map in which areas are distinctly coloured or shaded to represent classed values of a particular phenomenon. see also Choropleth maps

Topology – The description of how spatial features are connected to each other.

URL – Acronym for uniform resource locator. A standard format for the addresses of Web sites. For example: http://www.hantsiowcaddie.gov.uk. The first part of the address indicates what protocol to use (such as http: or ftp:), while the second part specifies the IP address or the host name (including the domain name) where the Web site is located. An optional third part may specify the path to a specific file or resource http://www.hantsiowcaddie.html

Ward – An electoral district or unit of local government. See: Super Output Areas

Web-based mapping – Maps created for use on the Internet so they often have some interactive functionality.

Web browser – An application that allows users to access and view Web pages on their computer screens. Web browsers enable users to view HTML documents on the World Wide Web.