Menu | Tools > TIN > Generate Coverage Boundary |
Pop-up | TIN Editor > Generate Coverage Boundary (Layers window) |
The Generate Coverage Boundary command is used to automatically create a polygon boundary to limit the extents of your TIN. This boundary encompasses only legitimate data and excludes any long edges or holes in the surface. This command is not used as part of TIN preparation, but is used to produce a geometry representing the data coverage for other purposes.
You can also create a coverage boundary manually using the Digitize Coverage Boundary command. See Coverage Boundary for more information.
Related commands:
Interface
The Generate Coverage Boundary command uses the following dialog box.
Option | Description |
Output layer | The feature layer on which the boundary feature is to be created. The drop-down list is populated with all feature layers currently open in the application. |
Edge length histogram | The Edge length histogram provides important statistical data on the lengths of the edges in the TIN you selected. TIN edge length values are grouped together according to edge lengths. Each group is displayed as a vertical bar in the histogram at the appropriate position along the horizontal axis. The shortest edges are in the first group along the horizontal axis and the longest edges are in the last group. The frequency or count of the edge length values included in each group is displayed along the vertical axis. There are two scale visualization methods for vertical axis data: • Logarithmic: displays the number of edges in a group over progressively exaggerated vertical intervals (for example, 10, 100, 1000, etc.). The intervals are based on the natural logarithm of the frequency. • Linear: displays the number of edges in a group over constant vertical intervals (10, 20, 30, etc.). When working with data containing many edges of similar length, it is recommended that you use the logarithmic scale. |
Cursor position | This field displays the length of the edge group at the current cursor position when moving the cursor over the histogram. |
Shortest edge | This field reports the shortest edge length in the TIN. |
Longest edge | This field reports the longest edge length in the TIN. |
Mean length | This field reports the mean length of the edges in the TIN. |
Standard deviation | This field reports the standard deviation of all the line lengths. |
Exclude all edges longer than: | The Exclude all edges longer than section is used to define the settings for excluding long edges during boundary creation. The application determines which edges to exclude based on the threshold value entered in the Exclude all edges... fields. The threshold value is the longest edge length you want to keep in the TIN. There are three options for the filter: • Mean + 2 x standard deviation, which excludes edges using the following formula: • User specified, where the user defines the longest edge length allowed, causing all edges longer than this value to be excluded. This option is defined by selecting the option and then either entering a value in the field or clicking the histogram to select a value. • Do not exclude any edges, where the boundary is generated without excluding any edges. If entering a specific value, it must be longer than the shortest edge length in the TIN. |
Procedure
1. Select the TIN Editor layer.
2. Select the Generate Coverage Boundary command.
The Generate Coverage Boundary dialog box is displayed.
3. Select the Output layer where the boundary is to be created.
4. Define the exclusion settings.
5. Click OK.
A polygon shape is displayed around the TIN in the Display window. If a threshold value was specified, any edges longer than the threshold will be outside of the boundary.
