GISP-E key terms

An organized system of hardware, software, data, people, and procedures used to capture, store, manage, analyze, and display spatially referenced information for decision-making and problem solving.

The academic discipline that studies the theory and concepts behind spatial data, including its representation, analysis, uncertainty, visualization, and the societal implications of geographic information technologies.

Information that records the location, shape, and relationships of features on or near the Earth's surface, usually stored as coordinates with associated descriptive attributes.

Descriptive, non-location information linked to spatial features, such as names, counts, dates, or classifications, typically held in tables and joined to geometry by a shared identifier.

A way of representing geographic features as discrete points, lines, and polygons defined by coordinate pairs, well suited to features with precise boundaries and attribute-rich records.

A representation of space as a regular grid of cells, each holding a value such as elevation or land cover, suited to continuous surfaces and imagery rather than discrete objects.

The set of rules describing spatial relationships among features, such as adjacency, connectivity, and containment, independent of exact coordinates, enabling network tracing and data quality checks.

A defined framework that assigns coordinates to locations on the Earth, combining a datum with a projection or geographic coordinate system so positions can be measured and shared consistently.

A mathematical transformation that converts locations on the curved Earth surface to a flat plane, inevitably introducing distortion in distance, area, shape, or direction.

A reference system that locates positions using angular units such as latitude and longitude measured from a datum, without flattening the Earth onto a plane.

A reference surface and set of parameters, such as an ellipsoid and its alignment to the Earth, against which coordinates are measured; mismatched datums cause positional shifts.

The ratio between distance on a map and the corresponding distance on the ground, commonly expressed as a representative fraction such as 1:24,000 or as a graphic bar.

The process of assigning real-world coordinates to spatial data, such as aligning a scanned map or aerial image to a known coordinate reference system using control points.

The manual or semi-automated conversion of analog maps or imagery into vector features by tracing points, lines, and polygons and recording their coordinates in a digital layer.

On-screen tracing of features directly over a georeferenced raster image or basemap in a GIS, replacing the older method of digitizing on a hard-copy tablet.

A container for spatial and attribute data, often relational, that stores feature classes, tables, relationship classes, and rules together and supports topology and validation within one managed structure.

A collection of spatial features of the same geometry type, such as all roads or all parcels, stored together with a common set of attribute fields in a geodatabase or similar store.

A widely used vector data format that stores geometry in one file and attributes in a linked table, along with index files, and lacks built-in topology or field name flexibility.

Structured documentation describing a dataset's content, source, accuracy, coordinate system, currency, and access constraints, enabling others to judge whether the data suit their purpose.

The degree to which spatial data meet stated requirements for positional accuracy, attribute accuracy, completeness, logical consistency, and temporal currency.

A measure of how closely the coordinates of features in a dataset match their true locations on the ground, often reported as a root-mean-square error against higher-accuracy reference data.

A record of the origin and processing history of a dataset, describing its sources, transformations, and methods so users can assess fitness for a particular use.

A statistic summarizing the average magnitude of positional or value errors, computed as the square root of the mean of squared differences between estimated and reference values.

A location with precisely known coordinates used to georeference imagery or maps and to check or improve the positional accuracy of the resulting spatial data.

The process of changing spatial data between formats, models, or coordinate systems, such as vector to raster or one file format to another, often with some loss of detail or attributes.

Conversion of vector features into a grid of cells, where each cell receives a value based on the features it overlaps, simplifying analysis but altering boundaries and precision.

Conversion of raster data into points, lines, or polygons, typically by tracing cell groupings or class boundaries, which can introduce jagged edges and require cleanup.

A set of techniques that examine the locations, attributes, and relationships of features to derive new information, such as proximity, overlay, density, or pattern detection.

Combining two or more spatial layers to create a new layer whose geometry and attributes reflect where input features coincide, used for suitability and intersection questions.

Creating polygons at a specified distance around features to identify areas within that proximity, commonly used for impact zones, service areas, and setback rules.

An operation that transfers attributes from one layer to another based on spatial relationship, such as containment or proximity, rather than on a shared key field.

Linking two tables by a common key field so records can be combined, without regard to location; the join succeeds only when key values match correctly.

Analysis of connected line systems to solve routing problems such as shortest path, closest facility, service area, or vehicle routing, respecting connectivity and impedance rules.

A topology-enabled line dataset prepared for routing, including connectivity rules, turn restrictions, and cost attributes such as travel time or distance used by network solvers.

A raster representation of ground surface elevation in each cell, used to derive slope, aspect, watersheds, and visibility, and to support terrain-based modeling.

Terrain derivatives computed from an elevation surface: slope is steepness in degrees or percent, and aspect is the compass direction a slope faces, both affecting runoff and solar exposure.

A terrain-based method that identifies which locations are visible from one or more observer points, accounting for elevation and line-of-sight obstruction by the surface.

Statistical methods applied to geographic data that account for location, used to describe patterns, detect clusters, and test whether observed arrangements differ from random expectation.

A statistic measuring spatial autocorrelation, indicating whether nearby values resemble each other (positive), differ (negative), or show no pattern, across a study area as a whole.

The tendency for values at nearby locations to be more similar or more different than expected by chance, a core property that violates assumptions of independent observations in standard statistics.

A technique that identifies statistically significant clusters of high or low values by comparing local conditions with the surrounding area, often using local autocorrelation statistics.

The deliberate arrangement of map elements, symbols, color, typography, and hierarchy so a map communicates its intended message clearly and truthfully to a defined audience.

The standard components of a map, including title, legend, scale indicator, north arrow or orientation, source credit, and projection note, that make it readable and accountable.

The graphic dimensions available for encoding data on a map, such as position, size, shape, color hue, color value, texture, and orientation, each suited to particular data types.

A thematic map that shades entire administrative or enumeration areas by a normalized value such as a rate or density, using color value to suggest magnitude.

Rules for grouping numeric data into map classes, such as equal interval, quantile, natural breaks, or standard deviation, each revealing different patterns in the same data.

Dividing a raw count by an area, population, or other base so mapped values are comparable across units of different size, preventing large areas or populations from dominating the map.

Simplifying and selecting features for display at a given scale, through operations such as smoothing, aggregation, displacement, and omission, so the map stays legible without misleading.

An open standard that serves georeferenced map images rendered from spatial data over the internet, allowing clients to request layers and styles without raw data access.

An open standard that delivers vector features with their geometry and attributes over the internet, enabling clients to query, style, and edit the underlying data rather than receive a picture.

A set of pre-rendered map images stored at fixed zoom levels and grid positions, served quickly to web maps; efficient for display but not for analysis or restyling.

The policies, standards, technologies, and organizational arrangements that let agencies and the public discover, share, and use spatial data across jurisdictions and systems.

A data storage model organizing information into tables of rows and columns linked by keys, supporting queries and integrity rules and widely used to hold spatial and attribute data.

The smallest distance or cell size at which data can distinguish detail; finer resolution captures more detail but increases storage and processing cost.

The ground dimensions of one raster cell, which determines the level of spatial detail a raster dataset can represent and the accuracy of analyses derived from it.