GIS Dictionary

[Euclidean geometry] A unit of angular measurement in which the angle of a full circle is 400 gradians and a right angle is 100 gradians. The common abbreviation for gradian … Read more

1 [geodesy] The ratio between vertical distance (rise) and horizontal distance (run), often expressed as a percentage. A 10-percent gradient rises 10 feet for every 100 feet of horizontal distance. … Read more

[geodesy] The direction of the maximum increase in gravity in a horizontal plane.

A map on which a range of colors indicates a progression of numeric values. For example, increases in population density might be represented by the increased saturation of a single … Read more

A map with symbols that change in size according to the value of the attribute they represent. For example, denser populations might be represented by larger dots, or larger rivers … Read more

[data capture] In ArcInfo Workstation, a parameter controlling the number of vertices and the distance between them on lines that represent curves. The smaller the grain tolerance, the closer the … Read more

1 [data quality] The coarseness or resolution of data. Granularity describes the clarity and detail of data during its capture and visualization. 2 [photogrammetry] The objective measure of the random … Read more

[graphics computing] An image produced by and stored in a computer as data for display.

[ESRI software] In MOLE, the most elementary part of a graphic. Icon, frame, and fill are examples of components that make up MOLE graphics.

[ESRI software] Text added in ArcMap layout view that exists in page space and is stored in a map document. Graphic text does not move if the extent or scale … Read more

1 [cartography] A network of longitude and latitude lines on a map or chart that relates points on a map to their true locations on the earth. 2 [astronomy] A … Read more

[symbology] A label positioning method in which labels are oriented along the graticule of the data frame. This is useful for maps of large areas, for cartographic or stylistic reasons.

[geodesy] A device used to measure small variations in the earth’s gravitational field between two or more points.

[geodesy] The science of deducing the size and shape of the earth by measuring its gravitational field.

1 [geography] A model that assumes that the influence of phenomena or populations on each other varies inversely with the distance between them. 2 [business] The idea that the probability … Read more

Any circle or near circle produced by the intersection of the surface of a sphere and a flat plane that passes through the center of the sphere. The equator and … Read more

[astronomy] The time at the prime meridian, which runs through the Royal Observatory in Greenwich, England. From 1884 to 1928, Greenwich mean time was the official name (and is still … Read more

The meridian adopted by international agreement in 1884 as the prime meridian, the 0-degree meridian from which all other longitudes are calculated. The Greenwich prime meridian runs through the Royal … Read more

[cartography] In cartography, any network of parallel and perpendicular lines superimposed on a map and used for reference. These grids are usually referred to by the map projection or coordinate … Read more

[ESRI software] In Survey Analyst for field measurements, any meridian that is parallel to the central meridian, used when computing points in planar rectangular coordinate systems of limited extent.

[cartography] The direction north along the north-south grid lines of a map projection.

[ESRI software] A mechanism for storing multivariate raster data in ESRI software, consisting of an ordered set of spatially overlapping grids (referred to as layers) referenced by an INFO file … Read more

[geodesy] A system of points with known positions, elevations, or both, used as fixed references in georeferencing map features, aerial photographs, or remotely sensed images.

[remote sensing] Communications equipment for receiving and transmitting signals to and from satellites such as Landsat.

The accuracy of remotely sensed or mathematically calculated data based on data actually measured in the field.

[Internet] In ArcGIS Online, a way to collaborate with other ArcGIS users and to exchange content related to a specific project or common activity.

[ESRI software] A group of several layers that appear and act as a single layer. Group layers make it easier to organize a map, assign advanced drawing order options, and … Read more

[geodesy] Acronym for Geodetic Reference System of 1980. The standard measurements of the earth’s shape and size adopted by the International Union of Geodesy and Geophysics in 1979.