TIN Data Area Delineation Command

Created:7/23/2001
Description:

Delineates the interpolation zone (data area) for a TIN.

Works as a command in ArcMap and ArcScene. You specify the maximum edge length for triangles that represent valid data. Triangles with edges longer than this will be marked as nodata. Outside, or nodata, triangles are not displayed in maps and scenes nor are they used in surface analysis.

This approach works pretty well when the data distribution forms a concave boundary but no study area polygon is available to 'clip' the TIN with. It helps to mark the long, skinny, triangles that tend to form around the perimeter (to complete the TIN's convex hull) as NODATA. This type of tool will tend to do most of the job but some touch up may be required. It's therefore considered to provide a semi-automated solution.


How to use:
  1. Add a TIN to a map or scene document. For this type of editing a map is probably more efficient. The TIN should not have any previous in/out classification performed by this command or through the use of clip or erase polygons.
  2. Execute the command and select the TIN in the resulting dialog's dropdown list.
  3. By examining the data distribution (e.g. using the ArcMap Measure tool) determine the maximum edge length for data triangles. For example, if all data points are gathered at a distance of 20 units or closer to each other than a maximum edge length of something a little larger than 20 would be appropriate.
  4. Specify the maximum edge length to use and press Apply. If you like what you see press Save. If not enough triangles were removed enter a smaller number and press Apply again. If too many triangles were removed press Revert, enter a larger number, and try again.
  5. There's an option to mark interpolation zone boundary edges as breaklines when the TIN is saved. In most cases you want this to occur. Breaklines serve to enforce the interpolation zone; preventing subsequent edits, such as node deletion, from disturbing it.
  6. The Data Area Delineation command's dialog is modeless. This state is chosen so you can use other exploratory tools (e.g. zoom, pan, measure) while being in the middle of the delineation process. You should not, however, use tools that would be editing the same TIN as there would be a potential for conflict.

    Steps for compiling the DLL:

  1. The VB code for this sample makes calls to one or more utility modules that are shared by a number of 3D samples. The shared modules are located in the 'Utilities' folder which is found directly below the main '3D Analyst' ArcObjects sample folder. In order to compile the DLL make sure you have the latest version of the shared modules installed.

Application:
ArcMap, ArcScene

Requires: A TIN that is not write protected in an ArcMap or ArcScene document.

Difficulty: Intermediate


Visual Basic
File Description
clsTinDataAreaDelineation.cls Implementation for TIN Data Area Delineation class.
frmTinDataAreaDelineation.frm Most of the work for the command is done in this form.


Key CoClasses: Tin, TinEdge
Key Interfaces: ITinEdit, ITinAdvanced, ITinEdge
Key Members: ITinEdit::SetTriangleOutsideDataArea