Available with 3D Analyst license.
The Modify Data Area tool from the TIN Editor defines the TIN by designating which
triangles participate inside or outside of the data area. Triangles
that are inside represent the TIN's interpolation zone whereas
triangles that are outside represent areas of no data. Select the Modify Data Area button 
to open the Modify TIN Data
Area dialog window.
From this dialog box, you can indicate whether you will select individual triangles by pointing at them or if you intend to select groups of triangles that are inside a digitized polygon. For these selected triangles, you can then indicate whether to make them inside or outside or to switch their current state with a toggle button.
There are three Selection Methods to interact with the triangles:
| Selection Method | Description |
|---|---|
Point within | Allows you to manually select the TIN triangle to modify. |
Within polygon | Allows you to select the TIN triangles that are within or cross the digitized polygon. |
| Completely within polygon | Modify the TIN triangles that are completely within a digitized polygon only. Triangles that are not completely within the digitized polygon will not be considered in the analysis. |
There are three Mask options to update the display of the triangles:
| Mask options | Description |
|---|---|
Set outside | You can set TIN triangles to be masked. If TIN triangles are masked, surface analysis and display treats this area as if it contains no data, even though the data remains. |
Set inside | You can set TIN triangles to be unmasked or show the elevation surface of the TIN. |
| Toggle current state | Changes the TIN triangles to either masked or unmasked depending on the current state. |
To modify the data area of a TIN, follow the steps outlined below:
- In the Contents pane, select the TIN layer you want to edit.
- Click the Data tab.
- Click the TIN Editor button
from the Data ribbon. - Click the Modify Data Area button .
The Modify TIN Data Area dialog box appears.
- Set the Selection Method and Mask properties for the TIN data area to be modified.
- Interactively select the triangles or the area of interest to modify.
- Click the Save button
to save the edits to the current TIN being edited. Once the TIN has been saved, all edits become permanent and cannot be undone. Click the Discard button 
to discard all unsaved edits. To create a copy of the TIN with the current edits applied click the Save As New TIN button 
. - Click the Close TIN Editor button
to close the TIN Editor when edits are completed.