Expand

Use the Expand option to increase (expand) or decrease (shrink) proportionally the size of a polygon by a given distance. It is possible to maintain the original polygon and create another polygon at the increased or decreased size. You can also specify the plane in which you want to work.

The expansion or contraction is performed such that the perpendicular distance between a line segment on the original polygon and the corresponding line segment on the expanded polygon is the user-defined distance.

If you maintain the original polygon and create an expanded copy, then you can check the perpendicular distance through using the Analyse/Angle Distance button on the Analyse toolbar.

This option can also be accessed by selecting the Expand button from the Modify toolbar.

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Instructions

On the Design menu, point to Polygon Edit, and then click Expand to display the following panel.

Expansion length

Enter the length by which to increase or decrease the polygon. A positive number will increase the size of the polygon, while a negative number will decrease it. When using a negative number, the resultant shape of the object may change if the specified value is greater than the object's actual width/radius. The unit of measurement does not need to be entered, as this will be the same as the units used in the database.

Repeat

Enter the number of consecutive polygons that are to be created.  Each polygon will be created at a separation distance specified in Expansion length.

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Figure 1 : Increasing the Original Polygon by 900m

Corner Method

	Connect offset edges with the intersection. Note that in some cases this could generate spikes.
	Connect offset edges with an arc, the discretisation of the arc will be based on the angle parameter below.
	Connect offset edges with a mitre, the maximum length (from the offset point) to the mitre is specified in limit below.

Line Method

	Both sides past end.
	Both sides up to the end.
	Single side.

Use Options

All together

All together disabled

With All together disabled the polygons will be expanded individually, and their orientation will be ignored. (Clockwise / counter clockwise polygons will both expand out if the expansion length is positive and both "expand" in if the expansion length is negative). Also, with all together disabled they are allowed to expand on top of each other.

All together enabled

With All together enabled, clockwise polygons will expand out and counter clockwise polygons will shrink in with positive expansion length. They will also join together.

Remove crossovers

Within a single layer, if a section exists where the line crosses itself then this option will remove the portion that is beyond the intersection point.

Remove crossovers disabled

Remove crossovers enabled

Use Projection Plane

Select this option to work in a plane other than plan view. Select the Plane method from the drop-down list to define a plane with the selected method. See below for explanations of the available plane methods.

To create a copy of a polygon, follow these steps:

1. Click Create copy.
   

2. Choosing a destination. You have three choices: the same layer, another existing layer, or a new layer.

   1. Same layer: Select the option to save it to the same layer by clicking Same layer.
      

   2. An existing layer: Leave the option Same layer unchecked. Use the drop-down list to select another existing layer the object will be copied to.
      

   3. A new layer: Leave the option Same layer unchecked. Type a new layer name into the Layer name textbox.
      

3. Click the Select button, then select the object(s) you want to copy.
   

4. Click Cancel on the context menu, or right-click anywhere in the Vulcan workspace to exit the Select mode and return to the Filter panel.
   

5. Click the Save button.
   

Important:   Be sure to save the changes to your Workbench session. If you do not save the changes any edits will be lost.