Trim by window box

This function deletes segments which are inside or outside a box that you create.

Prerequisites: Your view in Graphics is within 5% of Plan, Section, or Long section view, or the active plane (which can be an inclined plane).

To run this function: Choose Edit > Trim > Trim by window box, or...

• In the Function Chooser, type DELETE BY BOX, and press ENTER.

Fields on the Select and delete data form

Field	Description
Delete segments	partially. Deletes segments for which a part of the segment is inside or outside (depending on the inside/outside setting) the box that you drag in Graphics. entirely. Deletes all segments that are entirely within or outside of (depending on the inside/outside setting) the box that you drag in Graphics.
[inside/outside]	inside. The function operates on segments that are inside the box. outside. The function operates on segments that are outside the box.

You are prompted to drag a boundary box.

Notes:

• Only the segments which are within the active layer are affected.
• In Default preferences, the Window In Mode setting determines the way in which you define the boundary box in Graphics.

Output

The data you selected to delete is removed from Graphics, and the Select and delete data form is redisplayed.

Special Considerations

The rounding of coordinates to three decimal places when saving points to string files can sometimes cause problems with the locations of points relative to the string.

This sometimes results in points being located slightly (<0.002) on the wrong side of the boundary string. If this data is subsequently merged with the original boundary string, and used in the Create DTM function, spurious break line intersections may occur.

To overcome this, the boundary string is modified (transparently and temporarily for the duration of the Trim function only) by expanding or contracting each closed segment of the boundary string by an offset distance of 0.01. This ensures that spurious intersections will never occur.

The result of this adjustment is that strings which have been clipped to a boundary will never come closer than 0.01 to the boundary string.

1. offset = 0.01 2. original anti-clockwise boundary segment 3. original clockwise boundary segment x = location of new points at intersection with adjusted boundary -- = temporary adjustment of boundary segments

Extraction Type	Boundary String Direction	Modification
Inside	Clockwise	Contracted
Inside	Anti-clockwise	Expanded
Outside	Clockwise	Contracted
Outside	Anti-clockwise	Expanded

Trim by selected segment

This function deletes segments which are inside or outside a closed segment that you create.

Prerequisites: Your view in Graphics is within 5% of Plan, Section, or Long section view, or the active plane (which can be an inclined plane). A closed segment is displayed that you will use as the boundary.

To run this function: Choose Edit > Trim > Trim by selected segment , or...

• In the Function Chooser, type DELETE BY SEGMENT, and press ENTER.

Fields on the Select and delete data form

Field	Description
Delete segments	partially. Deletes segments for which a part of the segment is inside or outside (depending on the inside/outside setting) the box that you drag in Graphics. entirely. Deletes all segments that are entirely within or outside of (depending on the inside/outside setting) the box that you drag in Graphics.
[inside/outside]	inside. The function operates on segments that are inside the box. outside. The function operates on segments that are outside the box.

After you run this function, you are prompted to select an existing closed segment in Graphics.

Output

The data you selected to delete is removed from Graphics, and the Select and delete data form is redisplayed.

Trim by digitised segment

This function deletes segments which are inside or outside a temporary boundary that you create.

Prerequisites: Your view in Graphics is within 5% of Plan, Section, or Long section view, or the active plane (which can be an inclined plane).

To run this function: Choose Edit > Trim > Trim by digitised segment, or...

• In the Function Chooser, type DELETE BY TEMP SEGMENT, and press ENTER.

Fields on the Select and delete data form

Field	Description
Delete segments	partially. Deletes segments for which a part of the segment is inside or outside (depending on the inside/outside setting) the box that you drag in Graphics. entirely. Deletes all segments that are entirely within or outside of (depending on the inside/outside setting) the box that you drag in Graphics.
[inside/outside]	inside. The function operates on segments that are inside the box. outside. The function operates on segments that are outside the box.

You are prompted to digitise a temporary boundary string. To create the segment click the first two points then each subsequent point you click expands the closed segment. Press ESC to finish selecting points.

Output

The data you selected to delete is removed from Graphics, and the Select and delete data form is redisplayed.