View source for Help:Glossary

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This page contains a glossary of terms commonly used in XMS. Many of these terms have usage specific to XMS and may or may not coincide with how these terms are used elsewhere.

Typically the definition should correlate to the [http://water.usgs.gov/wsc/glossary.html USGS definition].

==A==
; [[Annotations|annotations]] : model used to add notes or references to world or screen coordinates.
; arc : sequences of line segments or edges, which are grouped together as a single "polyline" entity.
; arc group : multiple arcs that have been grouped together so they can be selected at once.

==B==
; bathymetry : the measurement of depth of underwater terrain.
; borehole : a deep, narrow hole made in the ground, especially to locate water. Can contain either stratigraphy data or sample data or both.
; boundary condition : a differential equation together with a set of additional constraint. Often abbreviated as BC. 
; breakline : a series of edges to which the mesh or scatter triangles should conform. A breakline is a feature or polyline representing a ridge, thalweg, or other shape to preserve in a surface made up of triangular elements or scatter set. In other words, a breakline is a series of edges to which the mesh or scatter triangles should conform to, i.e., not intersect.

==C==
; CAD : CAD (computer-aided design) is the use of computers for design.
; centerline :  arc that represents the direction of a river from upstream to downstream.
; compass plot : plot representing temporally varying vector data.
; contour : a curve along which the function has a constant value.
; coverage : groups of feature objects and attributes in the Map module.
; cross section : arcs used to extract elevations in SMS and WMS. In GMS, cross sections are flat surfaces used to visualize the subsurface.
; culvert : a structure that allows water to flow under a road, railroad, trail, or similar obstruction.

==D==
; DEM : a digital elevation model is a representation of a terrain's surface created from terrain elevation data.
; dialog : a window that pops up after a command is executed. May also be called a window, tool, or editor.

==E==
; element : used to describe the area to be modeled. Elements are formed by joining nodes. May be 1D, triangular, or quadratic.
; extrapolation : in the context of SMS, extrapolation is an optional feature to estimate a value when a scatter set does not bound the data to which it is being interpolated.

==F==
; feature object : patterned after Geographic Information Systems (GIS) objects and include points, nodes, arcs, and polygons.
; flow trace : animation technique used to visualize vector fields.

==G==
; graphics window : the main portion of the XMS program that gives a visual representation of the project.
; groin :  a rigid hydraulic structure built from an ocean shore (in coastal engineering) or from a bank (in rivers) that interrupts water flow and limits the movement of sediment.

==H==
; HY-8 : Culvert analysis program developed by the Federal Highway Administration.
; hydrograph :  a graph showing the rate of flow (discharge) versus time past a specific point in a river, or other channel or conduit carrying flow.

==I==
; isosurface : a surface of constant value extracted from a 3D dataset.

==J==
; jetty : a structure that projects from the land out into water.

==K==

==L==
; LiDAR : light detection and ranging.

==M==
; macro : button that executes a commonly used command.
; menu : a list of commands. Can be found at the top of the XMS interface or by right-clicking on items.
; mesh : a mesh consists of nodes that are grouped together to form elements. These nodes and elements define the computational domain of the numerical model. A numerical simulation requires a geometric definition of its domain. For many numerical analysis codes, this definition is a mesh.
; mesh element : mesh elements are used to describe the area to be modeled. Elements are formed by joining nodes. The element types supported vary from model to model.
; mesh node : a mesh node is the basic building block of elements in a mesh. A node consists of a location (X,Y) with an associated elevation. Other dataset values can also be associated with a node. The density of mesh nodes helps determine the quality of solution data and can be important to model stability.
; mesh nodestrong : a collection of nodes can be formed into a nodestring. Nodestrings are most commonly used to assign boundary conditions such as a flowrate or water-surface elevation. Nodestrings can also be used for mesh renumbering, forcing break lines, and boundary smoothing. Finally, a nodestring can store attributes pertinent to a location such as the total flow nodestring.

==N==
; node : define the beginning and ending XY locations of an arc.
; nodestring : a collection of nodes.

==O==
; observation :  display the variation of one or more scalar datasets associated with a mesh or grid.

==P==
; plot axes : a set of ruled lines oriented in either the world coordinate system or the grid coordinate system.
; point : XY locations that are not attached to an arc.
; polygon : a group of connected arcs that form a closed loop.
; project explorer : the portion of the interface that lists datasets and components of the project.

==Q==
; quadtree : a two-dimensional space partitioned by recursively subdividing it into four quadrants or regions.

==R==
; raster : data (usually elevation) stored in pixels.
; raster catalog : a table that allows assigning attributes to rasters.
; RST : a file which can be created by SRH-2D that can be used as initial conditions for an SRH model run.

==S==
; segment : the portion of an arc between two vertices or a node and a vertices.
; size dataset : defines the desired spacing of nodes in a spatial fashion.
; SMS : SMS (Surface-water Modeling System) is a program for building and simulating surface water models.
; spectral energy :  represents energy densities at discrete values over a range of angles and a range of frequencies for a given wave condition.
; SRH-2D : two-dimensional hydraulic, sediment, temperature, and vegetation model for river systems developed by the Bureau of Reclamation.
; SRH-2D monitor line : an internal polyline which may be used to monitor the total flow discharge through it. Monitor lines are applied the model to determine the flow and sediment flux across the lines at specified locations in the model. SRH-2D creates a file for each monitor line that details the bed and water-surface elevations, the flow, and the sediment flux across the lines. The monitor lines can be used to determine when the model reaches steady state conditions. For example, by comparing the predicted water-surface elevations over time and at various locations along the reach, the user can determine when the water-surface elevation reaches a steady state condition.
; SRH-2D monitor point : a monitor point is used to gather specific information for that location at all time steps. Information calculated by SRH-2D at a monitor point includes position in the X and Y direction, bed elevation, water elevation, water depth, X direction velocity component, Y direction velocity component, velocity magnitude, Froude number, and shear stress.
; SRH-2D simulation : a collection of objects used to define an SRH-2D model. An SRH-2D simulation must include a 2D mesh, boundary condition coverage, and material coverage. It may also include a sediment materials coverage, a monitor point coverage, and an obstructions coverage.

==T==
; TECplot : visual data analysis program which may be used to visualize results from the SRH-2D program.
; time series : a series of values of a quantity obtained at successive times.
; TIN : a triangulated irregular network that is a digital data structure used in a geographic information system (GIS) for the representation of a surface.

==U==
; UGrid : a module that uses an unstructured grid.

==V==
; vertex : XY locations along arcs in between the beginning and ending nodes.

==W==
; weir : a barrier across a river designed to alter its flow characteristics.

==X==
; [[XY Series Editor|xy series]] : curve defined by a list of x and y coordinates.

==Y==

==Z==
;{{anchor|zpts|Zpts|zpt|Zpt}}zpts
:A point with elevation, or vertical geometry, data attached to it. Also sometimes '''zpt'''.

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