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  4. Split Polygons Command

Split Polygons Command

The Split Polygons command of CivilGEO’s software allows the user to split one or more selected polygons into separate polygons using a cut polyline. When splitting polygons, make sure the cut polyline intersects completely through the selected polygon.

Note that because the software defines the storage areas, subbasins, and 2D flow areas using polygon shapes, the Split Polygons command can be used to divide them even further into smaller subareas.

Follow the steps below to use the Split Polygons command:

  1. From the Map Edit ribbon menu, select the Split Polygons command.
    Split polygons ribbon menu command
  2. The Split Polygons dialog box will be displayed.
    Split polygons dialog box

The following sections describe the Split Polygons command and how to interact with the above dialog box.

Selecting Polygons to Split

The Select Polygons to Split section allows the user to select the polygons to be split.

The user can click the [Pick] button to select the polygons (or other polygon shape elements) from the Map View. After selecting the polygons, the Pick polygons/storage areas/2D flow areas read-only field will display the number of selected polygons.
Pick polygons storage areas 2D flow areas read-only field

Alternatively, the user can preselect the polygons on the Map View prior to running this command. Upon running the command, the number of preselected polygons will be displayed in the Pick polygons/storage areas/2D flow areas read-only field.

Defining Cut Polyline

The Define Cut Polyline section allows the user to either draw or select an existing cut polyline from the Map View.

The following options are provided for defining the cut polyline:

Draw Cut Polyline

The Draw cut polyline radio button option allows the user to interactively draw a cut polyline on the Map View.

Follow the steps below to draw a cut polyline on the Map View:

  1. Select the Draw cut polyline radio button option and then click the [Draw] button. Alternatively, check the Create curvilinear polyline checkbox to draw the cut polyline using curvilinear segments.
    Draw Button
  2. The Split Polygons dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user what to do next.
  3. Draw the cut polyline on the Map View. While drawing polylines, the user can use the [Ctrl] key to switch between linear and curvilinear digitizing. Refer to this article in our knowledge base to learn more about the drawing elements on the Map View.
  4. After drawing the cut polyline, right-click and select Done from the displayed context menu.
  5. The dialog box will be redisplayed, and the status of the Draw cut polyline read-only field will change from Not Drawn to Drawn.

Pick Cut Polyline

The Pick cut polyline radio button option allows the user to select an existing cut polyline from the Map View.

Follow the steps below to select a cut polyline from the Map View:

  1. Select the Pick cut polyline radio button option and then click the [Pick] button.
    Pick button
  2. The Split Polygons dialog will temporarily disappear, and a prompt will be displayed on the status bar instructing the user what to do next.
  3. Select the cut polyline from the Map View. After selecting the cut polyline, right-click and select Done from the displayed context menu.
  4. The dialog box will be redisplayed, and the status of the Pick cut polyline read-only field will change from Not Selected to Selected.

After the cut polyline has been defined, the user can click the [OK] button. The software will split the selected polygon(s) along the defined cut polyline.

About the Author Chris Maeder

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