GMS:2D Grid Creation and Editing: Difference between revisions
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== Creating 2D Grids == | == Creating 2D Grids == | ||
Two types of 2D grids are supported by GMS, [[GMS:2D_Grid_Types|mesh centered and cell centered]]. The two main techniques used to create 2D grids are: the '''''Create Grid''''' command and the [[GMS:Map to Modules#Map to 2D Grid|'''''Map | Two types of 2D grids are supported by GMS, [[GMS:2D_Grid_Types|mesh centered and cell centered]]. The two main techniques used to create 2D grids are: the '''''Create Grid''''' command and the [[GMS:Map to Modules#Map to 2D Grid|'''''Map → 2D Grid''''']] command. A 2D grid can also be created from an existing 3D grid using the [[GMS:3D Grid Module#Converting 3D Grids to Other Data Types|'''''Grid -> 2D Grid''''']] command in the ''Grid'' menu of the [[GMS:3D Grid Module|3D Grid Module]]. A [[GMS:Importing/Exporting GIS Grids|GIS grid]] may also be imported. | ||
===Create Grid=== | ===Create Grid=== | ||
:A new grid can be created by selecting the '''''Create Grid''''' command from the ''Grid'' menu. This command brings up the Create Grid dialog. The options in the dialog are as follows: | :A new grid can be created by selecting the '''''Create Grid''''' command from the ''Grid'' menu. This command brings up the Create Grid dialog. The options in the dialog are as follows: | ||
:'''Origin, Length, Rotation''' | :'''Origin, Length, Rotation''' – By default, the rows and columns of 2D grids are aligned with the x and y axes. However, grids can be rotated about the z-axis, if desired. Thus, the information needed to determine the overall size and location of the grid is the xy coordinates of the lower left corner of the grid (the lower left corner prior to rotation), the length of the grid in the x and y directions, and the rotation angle. The xy coordinates of the origin are entered in the Origin edit fields, the dimensions are entered in the Length fields, and the angle of rotation is entered in the field entitled Rotation about Z-axis. | ||
:'''Bias''' | :'''Bias''' – Several options are available for defining the number and locations of the cell boundaries. A bias can be defined which controls how the cell size varies from one cell to the next. For example, an X bias of 1.5 causes each cell to be 50% larger than the previous cell when moving in the positive x direction. | ||
:'''Number of Cells''' | :'''Number of Cells''' – The total number of cells in each direction (number of rows or columns) can be defined by explicitly entering a number or by entering a base cell size and a limit cell size. The base and limit cell size options are used when a bias other than 1.0 is specified. The base cell size is the size of the first cell in the sequence. The cells are then generated by altering the cell size according to the bias until the limit cell size is reached. The remainder of the cells are constructed using the limit cell size. | ||
:'''Type and Orientation''' | :'''Type and Orientation''' – The controls at the bottom of the Create Grid dialog are used to define the type and orientation of the grid. The user can specify whether the grid should be a mesh-centered grid or a cell-centered grid. The orientation of the ij axes with respect to the XY axes can also be specified. | ||
===Map | ===Map → 2D Grid=== | ||
:The '''''Map | :The '''''Map → 2D Grid''''' command is used to construct a 2D grid using the feature objects in a 2D Grid Coverage. When the '''''Map → 2D Grid''''' command is selected, the Create Grid dialog appears. If a grid frame has been defined, the size and location of the grid frame are used to initialize the fields in the Create Grid dialog. In most cases, these values will not need to be changed and the user can simply select the OK button to create the grid. If a grid frame has not been defined, the size and location of the grid are initialized so that the grid just surrounds the currently defined feature objects. If desired, the grid dimensions can be edited prior to selecting the OK button to create the grid. | ||
:If one or more refine points are defined in the conceptual model, the number of rows and columns in the grid will be automatically determined when the grid is created. Thus, these fields cannot be edited by the user and will be dimmed. If refine points are not defined, the user must enter the number of rows and columns. | :If one or more refine points are defined in the conceptual model, the number of rows and columns in the grid will be automatically determined when the grid is created. Thus, these fields cannot be edited by the user and will be dimmed. If refine points are not defined, the user must enter the number of rows and columns. |