Abscissa: The separation between the vertical or y-axis and the x-coordinate along a horizontal axis in a rectangular coordinate system.

American Standard Code for Information Interchange (ASCII): A file format that stores and processes data using a range of numbers between 0 and 255.

Area: A description of a polygon’s size or contents.

Aspect: The direction of the slope of a terrain surface, measured clockwise starting north as 0 degrees to 360 degrees north again, with flat areas given a value of -1 or 0 degrees.

Asset Mapping: A capability that gives users a better and quicker visual view of where assets are located, along with the important information associated with every asset. Read full description.

Basemap: A georeferenced background image that serves as a point of reference on a map and provides visual context. A basemap cannot be edited.

Benchmark: A precisely surveyed site that is typically marked with a metal disk in the ground. Survey markers, geodetic marks, and control stations are other names for benchmarks.

Buffer: A proximity function that builds a polygon around a chosen feature or combination of features at a predetermined distance.

Cartography: The art, science, and study of depicting physical objects on maps by communicating spatial information.

Class: A grouping of data according to the range of values of a specific characteristic or attribute.

Coordinates: Pairs (X, Y) or triplets (X, Y, Z) of values used to represent points and features on a two- or three-dimensional surface.

Data: A group of facts, ideas, or instructions that have been formalized and are ready for processing by machines or by people. Generally used in the GIS field as a reference to all spatial information.

Data Field: A column in a data table.

Data Set: A collection of GIS data tables that are typically connected by a common system. A storm dataset, which includes manholes, lines, catch basins, detention basins, culverts, ditches, swales, and flow direction associated with stormwater runoff, is one example. The term dataset is also occasionally used to refer to an entire data collection.

Database Management System (DBMS): A group of technologies that make it possible to enter, store, output, organize, and utilize data while serving as an interface between users and databases.

Datum: A point of comparison for measuring locations on the earth’s surface. A datum defines where latitude and longitude lines come from and how they are oriented.

Digital Line Graph (DLG): A data format used and disseminated by the United States Geological Survey to represent geographic elements such as topography, hydrography, transportation, and man-made landmarks.

Documentation (GIS): Information describing a feature class, dataset, database, or associated processes. This might be demonstrated, for instance, by listing and defining feature attributes. Although metadata offers more in-depth information about geodata, it is frequently referred to as documentation.

Entity: A representation of a world point, line, or polygonal element in a specific geographic location. Examples include hospitals, fire hydrants, roads, state borders, rivers, and lakes.

Feature: A cartographic point, line, or polygon object with a spatial location in the real-world landscape that can be used in a GIS for storage, visualization, and analysis.

Field (Attribute Table): Characteristics used to describe each feature in a geographic data set, usually viewed as columns in a table.

Geocoding: The process of turning a description of a location, such as its physical address, into a precise location on a map, namely a pair of coordinates.

Geodatabase: A database or file structure used primarily to store, query, and manipulate spatial data. Geodatabases store geometry, a spatial reference system, attributes, and behavioral use data.

Geographic Information System (GIS): A computer-based tool that analyzes, stores, manipulates, and visualizes geographic information on a map, useful for finding spatial patterns, relationships, and trends. Read full description.

GIS Asset Mapping: A solution that integrates Geographic Information System technology and enhanced interactive image mapping to further improve the accuracy of tracking and mapping assets and work orders. Read full description.

GIS Lite: A general term frequently used to describe GIS products that are easier to use and have fewer features. GIS Lite tools are typically web-based and do not require specialized knowledge.

Georeference: An action that involves aligning an image, such as an aerial shot, to a recognized coordinate system so that it can be viewed and examined with other geographical data.

Horizontal Control Network: A network of known horizontal geographic positions that are oriented along plane coordinate axes, meridians, or other lines of orientation.

Hydrography: A term used to describe how lakes, rivers, and streams are represented geographically.

Infrastructure: The roads, cables, wires, pipes, bridges, canals, reservoirs, and sewers that support the economy and society.

Internet GIS: A network-based geographic information service that uses both wired and wireless internet to access and distribute geographic information, spatial analytical tools, and GIS web services.

Isogonic Line: A line joining points on the earth’s surface having equal magnetic declination as of a given date.

Join: An operation that appends the fields of one table to those of another through an attribute or field common to both tables. A join is commonly used to attach tabular data, such as work order counts or inspection results, to the attribute table of a spatial layer so the values can be mapped.

Kriging: A statistical interpolation method that uses standard location values to interpolate values at unknown locations and also estimates standard error and uncertainty.

Latitude: A term used to describe the north-south coordinates of locations on the earth. It ranges from 0 degrees at the equator to 90 degrees north or south at the poles.

Layer: The visual representation of a geographic dataset in a digital map. A layer is similar to a legend item on a paper map, containing groups of points, lines, or polygon features representing a particular class or type of real-world entity such as customers, streets, or postal codes.

Longitude: A coordinate term with values from 0 to 180 degrees east and west.

Map: A visual representation of phenomena with a global distribution. Symbols or signs may be used to represent the information being shown.

Map Legend: A pictorial representation of the symbology used in a map that explains to the reader what each polygon, line, point, and grid cell on the map stands for.

Meridian: A line of longitude that varies in east-west direction, ranging from 0 degrees to 180 degrees east and 180 degrees west.

Metadata: Information on the origin, accuracy, date, abstract, coordinate system, and other attributes of the data.

North Arrow: A graphical representation of which direction north is on the map.

Object-Based Image Analysis (OBIA): A method that allows users to segment images and classify them as a set of regions rather than as a set of pixels.

Parallax: A measure of the apparent shift in an object’s position when it is viewed from two different angles.

Polygon: A set of connected, closed lines that delineates a region’s perimeter and area, such as a lake, a forest, or the border of a nation.

QGIS: A free and open-source, fully featured GIS platform.

Query: A search of spatial or tabular data based on user-defined criteria, producing a subset of chosen records.

Raster Data: A data model used in GIS that typically consists of square or rectangular grid cells arranged in rows and columns.

Remote Sensing: The art and science of making measurements of the earth using sensors on airplanes or satellites.

Scale: The ratio or fraction between the distance on a map, chart, or photograph and the corresponding distance in the real world.

Scale Bar: A map element that shows the scale of a map graphically.

Set: A group of features and their data.

Shapefile: A simple format for storing the geometric location and attribute information of geographic features.

Slope: The elevation change or steepness of a surface with relation to change in location, measured in degrees or percent.

Spatial Data: Data that includes a geographic location component, allowing features to be linked geographically to a table by a unique identifier and displayed on a map.

Spherical Coordinates: A system based on a sphere defined by two angles of rotation in orthogonal planes, such as latitude and longitude in a geographic coordinate system.

Tabular Data: Descriptive information, usually alphanumeric, that is stored in rows and columns in a database and can be linked to spatial data.

Thematic Layer: A distinct spatial entity in a data layer that is usually delineated as points, lines, or polygons.

Topography: The study of the land surface. Topography describes a landscape’s mountains, valleys, rivers, and craters.

United States Geological Survey (USGS): A United States agency responsible for studying the landscape of the United States.

Universal Transverse Mercator (UTM): A standard set of map projections with a central meridian for each six degrees of longitude in width.

Vector Data Model: A common GIS feature representation of spatial information, based on defining coordinates and attribute information in points, polylines, and polygons.

Web GIS: A capability that allows the sharing of GIS data, maps, and spatial processing across private and public computer networks.

XY Data: Tabular records that contain coordinate values in an X field and a Y field. XY data can be plotted directly onto a map as a point layer without any prior digitizing, which is how spreadsheets of asset or inspection locations are commonly brought into a GIS.

Y Coordinate: The value that positions a point along the vertical or north-south axis of a coordinate system. In a geographic coordinate system the Y coordinate is the latitude; in a projected system such as UTM it is the northing, expressed in linear units from the origin.

Z-Value: The third value in an X, Y, Z coordinate triplet, most often representing elevation or depth above or below a defined vertical datum. Z-values allow a GIS to model terrain surfaces and to place assets such as buried pipe or multi-story equipment at their true height.

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