GIS Dictionary

A short line on a map that indicates the direction and steepness of a slope. Hachures that represent steep slopes are short and close together; hachures that represent gentle slopes … Read more

[symbology] On a topographic map, concentric contour lines drawn with hachures to indicate a closed depression or basin. Concentric contour lines drawn without hachure marks indicate a hill.

[printing] A continuous tone image photographed through a fine screen that converts it into uniformly spaced dots of varying size while maintaining the gradations of highlight and shadow. The size … Read more

A path through a network that visits each junction in the network only once and then returns to its point of origin. Hamiltonian circuits are named after the Irish mathematician, … Read more

A path through a network that visits each junction in the network only once without returning to its point of origin. Hamiltonian paths are named after the Irish mathematician, physicist, … Read more

[hardware] A small hardware device that provides the unique number used in the generation of a license file. The key is plugged into either the parallel or USB port on … Read more

[geodesy] Acronym for High Accuracy Reference Network. A regional or statewide resurvey and readjustment of NAD 1983 control points using GPS techniques. The resurvey date is often included as part … Read more

[linear referencing] In linear referencing, a group or category of hatch definitions.

[linear referencing] In linear referencing, a specification for where hatch marks are drawn on a line feature. Each hatch definition has its own set of properties that include the multiple … Read more

[linear referencing] In linear referencing, an organized collection of symbols and settings for the hatch definitions that make up a hatch class. Hatch styles are stored in a style file … Read more

[linear referencing] In linear referencing, a series of vertical line or marker symbols displayed on top of features at an interval specified in route measure units.

[linear referencing] In linear referencing, a type of labeling that posts and labels hatches or symbols at a regular interval along measured line features.

[geodesy] Acronym for horizontal dilution of precision. A measure of the geometric quality of a GPS satellite configuration in the sky. HDOP is a factor in determining the relative accuracy … Read more

[navigation] The direction of a moving object, expressed as an angle from a known direction, usually north.

[data capture] Manual digitization by tracing a mouse over features displayed on a computer monitor, used as a method of vectorizing raster data.

[computing] In computer programming, a variation on the binary tree data structure in which each node’s value is greater than the value of its leaf nodes. Sorting data in a … Read more

[standards] A metric areal unit of measure equal to 10,000 square meters. One hectare is equal to 100 ares or 2.47 acres.

[Euclidean geometry] The vertical distance between two points, or above a specified datum.

A geometric transformation that scales, rotates, or translates images or coordinates between any two Euclidean spaces. It is commonly used in GIS to transform maps between coordinate systems. In a … Read more

[ESRI software] In ArcGIS 8.3 and previous versions, a branch in the ArcToolbox tree providing overview help for ArcToolbox toolsets.

1 [astronomy] Half of a celestial body, such as the earth. 2 [Euclidean geometry] Half of a sphere.

[computing] In computer science, an algorithm that incorporates a shortcut or simplification for solving a programming problem, such as searching. While a heuristic may run faster than a more rigorous … Read more

[mathematics] A number system using base 16 notation, usually comprised of the digits 09 and the letters AF or af.

[computing] A database that stores related information in a tree-like structure, where records can be traced to parent records, which in turn can be traced to a root record.

[network analysis] A type of network attribute for a network element in a network dataset. Hierarchy can be used during network analysis to assign priority to a network element. For … Read more

[programming] A programming language that uses keywords and statements that are similar to expressions in human language or mathematics and is, therefore, easier for people to comprehend and use. A … Read more

In digital image processing, a spatial filter that blocks low-frequency (long-wave) radiation, resulting in a sharpened image.

1 [map design] Shadows drawn on a map to simulate the effect of the sun’s rays over the varied terrain of the land. 2 [map design] The hypothetical illumination of … Read more

[statistics] 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 … Read more

[digital image processing] The redistribution of pixel values in an image so that each range contains approximately the same number of pixels. A histogram showing this distribution of values would … Read more

[ESRI software] In Survey Analyst – Cadastral Editor, a parcel that has been replaced with a new parcel by subdivision, merge, or other means due to a change in the … Read more

[ESRI software] In ArcMap, a user-created reference to a time and date stamp. Historical markers can be used to easily connect to a historical version for a specific date and … Read more

[ESRI software] In ArcMap, a version that a user connects to by using a historical marker or indicating a particular date and time. Once connected, the version provides a read-only … Read more

[ESRI software] A model created, dated, and saved when the application is closed to document the tools and parameter values used for each session. The history model is contained within … Read more

[non-ESRI software] HKEY_CLASSES_ROOT registry hive. A Windows registry root key that points to the HKEY_LOCAL_MACHINE\Software\Classes registry key. It displays essential information about OLE and association mappings to support drag-and-drop operations, … Read more

[data quality] A small gap in a raster line feature, usually considered to be an error caused by the poor quality of a source document or by the scanning process.

[network analysis] In network datasets, a type of junction connectivity policy in which junctions connect to other junctions based on the edge connectivity policy set by the user; junctions “honor” … Read more

1 [navigation] The apparent or visible junction of land and sky. 2 [astronomy] The horizontal plane tangent to the earth’s surface and perpendicular to the line through an observer’s position … Read more

The circle containing all points equidistant from the center of an azimuthal projection.

[navigation] The angle formed by the intersection of two lines in a horizontal plane.

A network of known horizontal geographic positions, referenced to geographic parallels and meridians or to other lines of orientation such as plane coordinate axes.

[geodesy] A geodetic datum for any extensive measurement system of positions, usually expressed as latitude-longitude coordinates, on the earth’s surface. A horizontal geodetic datum may be local or geocentric. If … Read more

1 [computing] In a computer network, the computer that contains data being accessed by other computers. 2 [computing] A computer connected to a TCP/IP network such as the Internet. Each … Read more

[ESRI software] In ArcView 3.x, a tool for associating external files with a feature in a view. When a user clicks a feature in the view with the Hot Link … Read more

[non-ESRI software] A 32-bit integer returned from any member of a COM interface indicating success or failure, often written in hexadecimal notation. An HRESULT can also give information about the … Read more

[graphics map display] A color model that uses hue, saturation, and value. Hue specifies the perceived color, such as red or green. Saturation specifies the intensity, or how vivid the … Read more

[Internet] Acronym for Hypertext Markup Language. A markup language used to create Web pages for publication on the Internet. HTML is a system of tags that define the function of … Read more

[Internet] A computer file formatted with HTML tags so that it may be viewed in a Web browser and published on the World Wide Web. An HTML document may incorporate … Read more

[ESRI software] An ArcIMS viewer that uses a single ArcMap image or standard image service. The HTML viewer does not require a Java plug-in.

[Internet] 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.

[Internet] Acronym for Hypertext Transfer Protocol (Secure). A variant of HTTP enhanced by a security mechanism. It allows transactions such as e-commerce and data sharing to take place on the … Read more

[network analysis] A central node in a network for routing goods to their destinations.

The dominant wavelength of a color, by which it can be distinguished as red, green, yellow, blue, and so forth.

[geography] The field of geography concerning a range of social, cultural, and political aspects of human life as related to their distribution through physical space.

[surveying] A plane of reference for depths, depth contours, and elevations of foreshore and offshore features.

[geodesy] A survey of a water body, particularly of its currents, depth, submarine relief, and adjacent land.

[geodesy] The measurement and description of water features and their related land areas for the purposes of safe marine navigation.

[geography] The circulation of water from the earth through the atmosphere and back again. Its major stages are evaporation, condensation, precipitation, run-off, transpiration, infiltration, and percolation.

The study of water, its behavior, and its movements across and below the surface of the earth, and through the atmosphere.

A reference (link) from one point in an electronic document to another document or another location in the same document (the target). Activating the link, usually by clicking it with … Read more

[cartography] The study and representation of elevation and the earth’s topography.

[cartography] A curve showing the relationship of area to elevation for specified terrain. A hypsometric curve is plotted on a graph on which the x-axis represents surface area and the … Read more

[cartography] A map showing relief, whether by contours, hachures, shading, or tinting.

[map design] Relief or depth depicted by a gradation of colors, usually between contour lines. Each color represents a different range of elevation.

1 [geodesy] The science that determines the spatial distribution of elevations above an established datum, usually sea level. 2 [geodesy] The determination of terrain relief, by any method.