Methods for dividing channels (Maritime Charting)

The Divide Channel tool allows you to split an existing polygon feature into a specified number of sections. Each section maintains the attribute information from the feature you first selected. For example, a typical use of the tool would be to split an existing dredged channel into multiple channel features (the tool operates the same with any polygon feature).

Dividing channel features into multiple parts

The Divide Channel tool allows you to specify the following:

• The number of channels that will be generated from the selected feature
• The selection tolerance (in pixels) that will be used in the divide channel corner identification process

The tool snaps to the vertex within the search tolerance whose angle relative to the previous vertex most closely approximates a right angle. The default value setting is 7.

Before the divide channel process is run

While defining points

After process is executed

Choosing the divide method

There are two methods to divide a channel: Equal Distance and Thiessen.

Equal Distance

This option cuts the channel by first generating a series of straight line segments connecting one side of the channel to the other. It does not allow the segments to cross each other. It then creates the split lines by dividing these line segments into N equal parts, N being the number of divisions+1. The points at which the line segments are divided are used as the vertices of the cut lines used to divide the channel.

注:

The Resolution slide bar is only available for the Thiessen method.

Thiessen

This option cuts the channel by first generating a series of buffers around the sides of the channel to create each cut line. The intersections of the buffers are used as the vertices of the cut lines used to divide the channel. This option takes Resolution as input; you can increase or decrease the resolution to control the number of buffers used. This option is named Thiessen, as it is similar to generating Thiessen polygons, but instead of generating polygons around points, it generates lines between lines.

Defining the direction of the channels using the anchor point

While running the Divide Channel tool, you need to specify the direction in which you want to split the channel. You can determine the direction according to the length or the width of the selected feature. To determine this, you define the first point, also known as the anchor point, followed by the second, third, and fourth point. The direction of the channels is always established perpendicular to the line between the anchor point and second point.

Maintenance of attribute information

After running the Divide Channel tool on a selected polygon, the original feature is discarded, and new features are inserted. The new features maintain the same attribute information as the original feature with the exception of the system-populated attributes, such as NAME and LNAM. These attributes are populated with different values on each feature to ensure data integrity.