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  4. Buffer Polylines Command

Buffer Polylines Command

The Buffer Polylines command of CivilGEO’s software allows the user to create new polygons around the selected polylines using a specified buffer distance.

Note that the user can also create a buffer around selected polygons using the Buffer Polygons command. To learn more about this command, refer to this article in our knowledge base.

Buffered features are stored in user-specified target layers, which must contain either line or polygon features. For instance, the user might use buffers to show an ecological zone around a waterway or the area around a contaminated well. More than one feature can be buffered at once, but a separate buffer will be created around each feature.

Follow the steps below to use the Buffer Polylines command:

  1. From the Map Edit ribbon menu, select the Buffer Polylines command.
    Map edit ribbon menu
  2. The Buffer Polylines dialog box will be displayed.
    Buffer polylines dialog box

The following sections describe the Buffer Polylines command and how to interact with the above dialog box.

Selecting Polylines

The Select Polylines section allows the user to select polylines to buffer from the Map View. The user can click the [Pick] button to select polylines from the Map View.
Selecting polylines

After selecting the polylines, the number of selected polylines will be displayed in the Pick polylines read-only field. Note that if polylines were pre-selected prior to running this command, then the Pick polylines read-only field will display the number of selected polylines.

The user can click the [Clear] button to cancel any previous selection and redo the entire process.

Buffer Polyline Options

This section allows the user to specify the buffer distance, corner type and shape of the buffer at the end of the polylines.
Buffer polyline options

The following entries are provided in this section:

  1. Buffer distance
    This field allows the user to enter the buffer distance. The buffer distance can be entered as a number (equal for all input polylines) or a numeric field. No negative buffer distance is accepted. Alternatively, the user can click the [Pick] button to measure the buffer distance from the Map View.
  2. Corner type
    This dropdown combo box allows the user to select the shape of the buffer at corners where two polylines join. The following options are provided:

    • Bevel The buffer shape for inner corners will be squared while the outer corner will be cut perpendicular to the furthest point of the corner.
    • Miter The buffer corner shape will be a square or sharp around corners.
    • Round The buffer shape for inner corners will be squared while the outer corner will be round. By default, this option is selected.
  3. End cap type
    This dropdown combo box allows the user to select the shape of the buffer at the end of the polyline. The following options are provided:

    • Butt The buffer will have an end cap perpendicular to the end of the selected polyline.
    • Round The buffer will have an end cap that is round at the end of the selected polyline. By default, this option is selected.
    • Square The buffer will have a square end cap around the end of the selected polyline.
  4. Dissolve (merge) overlapping buffered polygons
    On checking this checkbox, the boundaries of the intersecting buffers will be dissolved. The original attributes will not be preserved if this option is used. This option will merge overlapping buffered objects into a single object.

Map Layer Details

This section allows the user to create a new general drawing layer or a GIS layer for the buffer polygons. By default, the software places the buffer polygons in the Default Drawing Layer. When creating a GIS layer, the polygons are saved as a shapefile.
Map layer details

The following entries are provided in this section to define the type and name of the map layer:

  1. Layer type
    This dropdown combo box defines the type of layers that can be created. The following options are provided:

    • Drawing
      This option is used to draw a vector entity of buffer polygon. This type of layer is identical to the Default Drawing Layer that is defined in the Map Data Layers. By default, this option is selected.
    • GIS
      This option is used to create a GIS layer for creating a shapefile of the buffer polygons. This data is stored within an external shapefile.
  2. Layer name
    This field defines the layer name that will be displayed in the Map Data Layers panel. Duplicate layer names are not permitted. The user can click the [New] button to define a new layer name.

GIS Layer Details

This section gets enabled when the user selects a GIS layer type. Otherwise, the options in this section are not available.
GIS layer details

The Directory field defines the path and name of the shapefile to be created. The user can click the […] browse button to select the shapefile directory and file name.

The Schema definition data table allows the user to define the fields to include for the shapefile layer.

This data table requires the following data:

  1. Field Name
    This data column is used to define the field name to add to the shapefile layer.
  2. Field Type
    This dropdown combo box is used to select the data type of the field defined above. The following data types are provided:

    • Floating Point
    • Integer
    • Text
    • Date
  3. Width
    This spin control button is only available for text field types and has a default value of 80. This spin control can range from 1 to 255. The strings longer than the field width that do not fit into the field format will suffer truncation.

Creating Buffer Polygons

When all the data have been defined in the dialog box, the user can click the [OK] button and the software will create buffer polygons around the selected polylines.

About the Author Chris Maeder

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