GISI Foundation key terms

A computer-based system for capturing, storing, checking, integrating, manipulating, analyzing, and displaying data that is referenced to locations on the Earth's surface, used to support decisions and solve spatial problems.

Any information that records the location, shape, and attributes of features or phenomena on or near the Earth's surface, allowing position-based querying, measurement, and mapping.

Non-spatial descriptive information linked to geographic features, such as names, counts, dates, or measurements, stored in tables and joined to geometry through a shared identifier or record number.

The process of assigning real-world coordinates to spatial data so that features align correctly with a known coordinate reference system and can be integrated with other geographic datasets.

A defined framework that specifies how coordinates relate to positions on the Earth, combining a datum, an ellipsoid, units, and sometimes a projection, so locations can be recorded and exchanged consistently.

A coordinate reference system that locates positions on the curved Earth using angular units, typically latitude and longitude measured in degrees from a datum's equator and prime meridian.

A coordinate reference system that converts positions from the curved Earth onto a flat plane using a map projection, expressing locations as linear eastings and northings in metres or feet.

A mathematical transformation that systematically converts positions on the curved Earth to a flat surface, necessarily introducing distortion in distance, area, shape, direction, or some combination of these properties.

A reference surface, defined by an ellipsoid and its position relative to the Earth, from which coordinate measurements are made; different datums shift coordinates by tens to hundreds of metres.

The unavoidable change in distance, area, shape, or direction that occurs when the curved Earth's surface is represented on a flat map, varying in type and magnitude across the mapped area.

A representation of geographic features as discrete geometric objects, specifically points, lines, and polygons, each carrying attributes and stored as coordinates in a structured format.

A representation of geographic space as a regular grid of cells, each holding a value for a phenomenon such as elevation, land cover, or imagery, with resolution set by cell size.

The set of rules describing spatial relationships between features, such as adjacency, connectivity, and containment, independent of their exact coordinates, used to maintain data integrity and support network analysis.

A structured container for storing spatial and attribute data together, supporting rules, relationships, domains, and topology, and typically managed by a relational database management system.

A data storage system that organizes information into tables of rows and columns, linked through shared key fields, allowing flexible querying and maintaining consistency across related datasets.

Structured descriptive information about a dataset, covering its content, source, accuracy, coordinate system, lineage, and access conditions, enabling others to find, evaluate, and use it appropriately.

A record of the origin and processing history of a dataset, documenting sources, transformations, and methods applied so that users can assess suitability and reproduce results.

The degree to which spatial data meets stated requirements for accuracy, completeness, consistency, resolution, and currency, determining how reliably the data can support analysis and decisions.

A measure of how closely the recorded coordinates of features match their true positions on the Earth, commonly expressed as an error distance at a stated confidence level.

A set of techniques that examine the locations, attributes, and relationships of geographic features to reveal patterns, test hypotheses, and support decisions that location-based reasoning can inform.

The automated execution of spatial operations, such as buffering, clipping, intersecting, or dissolving, on geographic data to create new datasets and derive information.

A technique that combines two or more spatial layers to produce a new layer whose geometry and attributes reflect the intersections of the inputs, used to examine coincident conditions.

A polygon generated at a specified distance around a point, line, or area feature, used to identify or analyze locations within a defined proximity of that feature.

A family of methods that solve routing problems on connected line systems, such as finding shortest paths, service areas, or optimal routes subject to impedance and connectivity constraints.

The deliberate arrangement of map elements, including symbols, colours, typography, scale, and layout, to communicate geographic information clearly and appropriately to an intended audience.

The relationship between distance on a map and the corresponding distance on the ground, expressed as a representative fraction, a verbal statement, or a graphic bar.

A key that explains the symbols, colours, and classifications used on a map, allowing readers to interpret features and thematic values correctly.

The set of visual conventions, including colour, shape, size, and pattern, used to represent features and attribute values on a map so that meaning is conveyed accurately.

The simplification and abstraction of spatial data for display or analysis at smaller scales, reducing detail while preserving the essential character and structure of the features shown.

A location with known coordinates used to georeference or verify spatial data, providing the anchors needed to transform an unreferenced dataset into a defined coordinate system.

Angular coordinates that specify position on the Earth, with latitude measuring distance north or south of the equator and longitude measuring distance east or west of the prime meridian.

The equipotential surface of the Earth's gravity field that approximates mean sea level, used as the reference for vertical measurements and as the basis for many horizontal datums.

The ground dimensions represented by one raster cell, which determines spatial resolution; smaller cells capture finer detail but increase storage and processing demands.

The policies, roles, standards, and processes that control how spatial data is created, maintained, shared, secured, and retired across an organization, ensuring accountability and consistent quality.

The professional obligations guiding responsible use of spatial data, including protecting privacy, avoiding misuse of location information, disclosing uncertainty, and respecting legal and community interests.

The staged sequence of activities in a GIS project, from requirements definition and data acquisition through analysis, quality control, delivery, and maintenance, with reviews at each stage.