SMS:Scatter Menu

The items in the Scatter menu in the Scatter module are described below. The menu items all work with the active scatter set unless otherwise noted.

General Commands

Scatter Options

Scatter options are accessed through the Scatter menu, Scatter Options dialog in the Scatter Module.

Triangulation Options

This section lets the user adjust the maximum aspect ratio of a thin triangle. The aspect ratio is the ratio of the triangle width to the triangle height. All triangles with an aspect ratio less than what is specified are considered thin.

Long Triangles

This section contains options for deleting or selecting long triangles.

Individual Points

This section contains the Retriangulate voids when deleting option. When scatter points are deleted, the triangles attached to the scatter points (if any) are also deleted. If this option is on, surrounding triangles are retriangulated to fill the void.

Triangulation Optimization Options

When the optimize triangulation command is invoked, the triangles are optimized in one of two ways:

• Angle Optimization – The triangles are swapped to conform to the Delaunay Criterion.
• Area Optimization (SHOALS) – The triangles are swapped to align with other triangles. The swapping is done by comparing the area of one triangle to its neighbor. The user sets a Bias. If the area of the smaller triangle is less than the area of the larger triangle divided by the bias, the triangles are swapped. This is useful for optimizing the triangulation of surveys such as SHOALS surveys.

Duplicate Vertex Options

When the Select/Delete Duplicate Points menu item is selected, points within a tolerance of other points are selected or deleted. The user sets the Tolerance and whether to delete or select the points when the command is invoked.

Delete Scatter Set

This option is found in the Scatter module in the Scatter menu. If one scatter set exists, the user will be asked if they want to delete the active scatter set. If more than one scatter set exists, a dialog appears. The scatter sets can be flagged for deletion in this dialog. Double-clicking on a scatter set in the window or pushing the Delete button flags or unflags a scatter set for deletion. Select All or Deselect All will flag or unflag all sets. A set is flagged if the letter "d" appears to the left of the scatter name.

Merge Scatter Sets

Multiple scatter sets can be merged into a single scatter set using the Merge Scatter Sets dialog. The menu command Scatter | Merge Sets opens the Merge Scatter Sets dialog.

Selecting scatter sets to merge

The Merge Scatter Sets dialog contains a spreadsheet listing all of the scatter sets currently loaded into SMS. Scatter sets to merge are specified by checking the Merge box in the Merge column of the spreadsheet. When merging scatter sets, only one dataset is transferred to the merged scatter set. The dataset to be transferred is specified for each scatter set in the Dataset column of the spreadsheet.

The Priority column of the spreadsheet is only used if the Overlapping region option is set to Delete lower priority scatter points. This option is explained below.

Merge Options

The following options are available when merging scatter sets:

Merged scatter set options

• Name – Specify the name for the new, merged scatter set.
• Delete original scatter sets – The scatter sets to be merged are deleted after the new, merged set is created.

Overlapping region options

• Merge all scatter points – All scatter points from all scatter sets to be merged are combined into one set and retriangulated.
• Delete lower priority scatter points – In regions where scatter points and triangles overlap, the scatter points and triangles from the lower priority scatter set are deleted. The priority is based on the Priority column of the Select scatter sets to merge spreadsheet. The Move up and Move down buttons can be used to adjust the priority of the scatter sets when this option is selected.
  • Maintain triangulation – The triangulation of the original scatter sets is maintained. New triangles are created to connect the original scatter sets into a single, merged scatter set.

Merge Report

When the merge finishes a merge report will be displayed on the screen. This report shows statistics for the scatter sets that were merge such as number of vertices and triangles before and after the merge. If desired vertices are being deleted, check the duplicate points tolerance. This is found at Scatter→Scatter Options dialog.

Create Scatter Subset

All selected points from the original scatter set are moved from the original set into a new scatter set. The user is prompted for the name of the new scatter set. If all points for the current scatter set are selected, nothing occurs. The two scatter sets, the original and the new, are retriangulated.

Interpolate to Mesh

If mesh nodes exist, the Interpolation Dialog appears where the user sets the interpolation options. The scatter point datasets are then interpolated to the mesh nodes using the user specified interpolation options.

Interpolate to Cartesian Grid

If a cartesian grid exists, the Interpolation Dialog appears where the user sets the interpolation options. The scatter point function values are then interpolated to the center of each grid cell.

Interpolate to Scatter Grid

If a scattered dataset exists, the Interpolate to Scatter Grid menu item (Scatter module, Scatter menu) brings up the Grid Frame dialog. The user positions the purple grid frame and sets up the number of rows and columns in the grid. When the user pushes OK, a new scatter set is created with scatter points at the corners of each grid cell. The original scatter set is interpolated to the new scatter grid set using linear interpolation.

Using the scatter grid is a form of data decimation: a dense scatter set can be represented as a less dense scatter set.

Interpolate to Nautical Grid

This option creates a nautical chart. A nautical chart divides a scatter set into bins and finds the maximum, minimum, and average depth over each bin. The Interpolate to Nautical Grid menu item (Scatter module, Scatter menu) brings up the Grid Frame dialog. The user positions the purple grid frame and sets up the number of rows and columns in the grid. When the user pushes OK, a new scatter set is created with scatter points at the center of each grid cell. Three functions are created for each scatter point from the active scalar function of the original scatter set:

• Average – The average depth over each bin.
• Minimum – The minimum depth over each bin.
• Maximum – The maximum depth over each bin.

Requirements to Interpolate to a Nautical Grid

1. A scatter dataset must exist.
2. Active coverage type must allow grid frames to be created. The Cartesian Grid Module model coverage types allow the creation of grid frames.

Interpolate from Other Scatter

This option interpolates one scattered dataset to another set. Two sets must exist for this option to be enabled. A dialog appears and the user selects the scatter set to interpolate from. That scatter set is interpolated to the active scatter set. The Options button brings up the Interpolation Options dialog, allowing the user to set the interpolation type. The interpolation uses an extrapolation value of 0.0.

Related Topics

• Scatter Module
• Scatter Module Menus