SMS:Cartesian Grid Module Overview

The 2D Cartesian Grid Module contains tools used to construct 2D Cartesian finite difference grids. These grids consist of cells aligned with a rectilinear coordinate system.

Some models limit the grid to be defined with square cells, others limit to constant sized rectangular cells, while others add the flexibility of having variable sizes to the cells (variable row height or column width. It is used to create, edit, and visualize rectilinear grids. Datasets can have values at cells, corners, and midsides.

Functionalities

The 2D Cartesian Grid Module contains tools used to construct 2D Cartesian finite difference grids. These grids consist of cells aligned with a rectilinear coordinate system.

Some models limit the grid to be defined with square cells, others limit to constant sized rectangular cells, while others add the flexibility of having variable sizes to the cells (variable row height or column width.

It is strongly recommended that grids be created through the Map Module. The grid module currently includes interfaces for:

• BOUSS-2D – phase resolving Boussinesq wave energy and circulation model
• CMS-Flow – hydrodynamic circulation specifically adapted for coastal zone
• CMS-Wave – wave energy model
• STWAVE – wave energy model
• TUFLOW – Coastal, Riverine, and Urban hydrodynamic model with emphasis in flooding applications

Grid Types

Types of 2D Grids Supported by models SMS. (a) Mesh-Centered Grid (b) Cell-Centered Grid. In Cartesian grids, row and column boundaries are straight. Each cell center or grid node can have a unique elevation. The grid can also be rotated about the Z axis if desired.

File:GridType1.bmp

Types of 2D Grids Supported by SMS models: (a) Mesh-Centered Grid, (b) Cell-Centered Grid.

Creating and Editing 2D Grids

Create Grid. A new grid can be created by selecting the Create Grid tool from the Cartesian Grid Tools. With this tool active, the user can create a grid by clicking on three points in the graphics window. The first click defines the origin of the grid, the second click defines the orientation of the grid and length of the I axis and the third click defines the length of the length of the J axis. Once the user clicks three times defining the three points, the Map → 2D dialog appears.

Editing 2D Grids. Each of the cells in a 2D grid can be active (water) or inactive (land). An inactive cell is ignored when contours or vectors are displayed on the grid and by the numeric engine during computation. If a cell has the potential of becoming active (due to wetting/drying or a similar process), it should be classified as active. Cells status is specified by selecting the cell and assigning a status through the model menu.

Rows and columns can be added to an existing grid that supports variable row/column size by using the Insert Row, Insert Column, Drag Row, or Drag Column tool. (See 2D Grid Tool Palette)

Smoothing 2D Grids

It may be useful to smooth the spatial data stored on a 2D grid for a number of reasons. These reasons include:

• In order to conserve the amount of disk spaced required to store a DEM, many DEM formats store elevations rounded to the nearest integer value. This causes elevation changes to occur in discrete steps rather than smoothly, as would be the case in nature. In regions of low relief, rounded elevations can cause an area to be artificially "flat."
• Surveys may include anomalies. Smoothing algorithms blend these bad data points into the surrounding values.
• Datasets may include spurious noise either from physical conditions such as waves or numerical filtering. Smoothing can dampen these variations.

When you right-click on the grid in the Project Explorer, operations for the grid appear in a pop up window. One of these is the smooth operation.

Converting 2D Grids

2D Grids may be converted to other types of data used in SMS, such as a Scattered dataset of 2D mesh. 2D Grids can be converted by right-clicking on the grid in the Project Explorer.

Project Explorer

The following Project Explorer mouse right-click menus are available when the mouse right-click is performed on a Cartesian Grid Module item.

Cartesian Grid Module Root Folder Right-Click Menus

Right-clicking on the Cartesian Grid module root folder in the project explorer invokes an options menu with the following options:

• Display Options

Cartesian Grid Item Right-Click Menus

Right-clicking on a Cartesian Grid item in the Project Explorer invokes an options menu with the following module specific options:

• Smooth – Opens the Cartesian Grid Smoothing Options Dialog.

File:Create Transformed Grid.jpg

Create Transformed Grid dialog

Model Specific Right-Click Menus

• Create Transformed Grid

Opens the Create Transformed Grid dialog. Creates a copy of the grid with a rotated origin. Used to change the I direction for wave models.

Related Models: CMS-Wave, STWAVE

Menus

The Cartesian Grid Module Data Menu commands include:

Model Specific Menus

• BOUSS-2D
• CMS-Flow
• CMS-Wave
• STWAVE
• TUFLOW

Model Commands

• Steering Module
• Switch Current Model

Dataset Commands

• Data Calculator
• Dataset Toolbox
• Create Datasets
• Map Elevation
• Zonal Classification

Visualization Commands / Options

• Contour Options
• Vector Options
• Film Loop

Data Conversion Commands

• Grid → Scatterpoint
• Grid → Map
• Grid → Mesh

Grid Commands

• Find Cell

Module Tools

When active, the Cartesian Grid module has several tools located in the tool palette. See Cartesian Grid Tools to learn more.

How do I?

To learn more about how to use the Cartesian Grid Module go to the Tutorials section of the Aquaveo website at: http://www.aquaveo.com/software/sms-learning-tutorials.

Related Coverages

The grid module currently includes interfaces for:

• BOUSS-2D – phase resolving Boussinesq wave energy and circulation model
• CMS-Flow – hydrodynamic circulation specifically adapted for coastal zone
• CMS-Wave – wave energy model
• STWAVE – wave energy model
• TUFLOW – Coastal, Riverine, and Urban hydrodynamic model with emphasis in flooding applications