Polygonal Restriction
In the Polygonal Restriction tab of the DTM Thickness form, select the Restrict to Polygons check box option if you want to restrict the triangulation to the areas defined in a String file or Outline file.
If you chose a String file, double-click (or click on the List icon) to select the name of the X, Y field names. If the constraint is defined by multiple strings, double-click to select a Join field and (optionally) a String field.
Points occurring outside the region enclosed by the polygons will not be used when the DTM is created.
String File
Select a file Type and then double-click (F3) to select the input File that contains the polygons you want to use to restrict the data. Optionally, apply a Filter to limit the records to a particular subset of data.
X, Y, Z fields
Double-click (F3) to specify the names of the fields in which the Easting, Northing and Z coordinates are stored.
Join field
In forms that require polylines as an input, the values in this field define whether the data points in the input file should be joined by a line. If successive records have the same value in this field, a line will join the points. If two-factor topology is required, the values in a String field may also be used to segment the lines.
String field
In most forms, the String field is an optional generic attribute used to store a secondary input such as a code. Traditionally, this field has also been used with the Join field to define whether data points should be joined by a line, or strung, hence the name.
Outline File
If you have selected Outline file as the boundary file type, specify the name of the file containing the outlines you want to use to restrict the process.
Restrictions
For up to 5 outlines, choose either NAME or CODE from the Select by list and either:
- double-click in the Identifier input box to select an outline, or
- use wildcards to select multiple outlines.
By default all outlines in the specified Outline file will be used if no selection criteria are specified.
For more information, refer to the Outline Restrictions topic.