Menu | Tools > Layers > Compute Layer |
Pop-up | coverage root > Compute Layer (Layers window) |
Create a new attribute layer for an existing coverage. An expression can be applied to source data to alter the attribute values in the new attribute layer. This is useful if you need to apply a shift, but do not want to apply it to all attributes in a coverage. See Filter Expressions for information on creating expressions.
Related commands:
Interface
The Compute Layer command uses the following dialog box.
The fields in this dialog box include:
Option | Description |
Layer Name | The name to assign to the new layer. |
Layer Z-axis Convention | The Z-axis convention for the data in the new layer. The options include: • Depth with Z-axis positive down: to be used if the data in the new layer will contain depth values that are positive down. • Height with Z-axis positive up: to be used if the data in the new layer will contain elevation values that are positive up. • Not applicable. Generic numbers: to be used if the data in the new layer will represent generic, non-Z values (for example, Std_Dev). These values display as spikes and dips in the data. |
Available Attributes | All attributes available in the selected coverage. These attributes are used as the source data for creating the new layer. |
Expression field | Define the expression to use to create new values in the new layer. 1. Double-click an attribute in the Available attributes list to add it to the expression field. If the selected attribute has a space in its name, you must place quotation marks around the attribute in the expression field (for example, “attribute name”). 2. Click the operator buttons (+, -, x, \, ^ or brackets) or manually type operators to add them to the expression field with the attribute name. 3. Type any necessary values for the expression operators. The Clear button can be used to delete the expression and start over. |
Procedure
1. Select the Compute Layer command.
The Compute Layer dialog box is displayed.
2. Type a Name for the new layer.
3. Select the Z-axis convention for the layer.
4. Double-click the attribute to use as the data source for the new layer.
5. Define an expression.
6. Click OK.
A new layer is added to the Layers window, populated with values from the source attribute that have been altered according to the user-specified expression.
