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User Documentation for the Split Line Tool

The Split Line Tool (implemented in the BisectorWidget) is designed to help you split a line feature in QGIS based on a specified distance. Using an easy-to-use interface, you can choose a split length, set the orientation (from the start or end of the line), select units of measurement, and then apply the split. The tool also automatically creates a visual layer that shows the start and end points of the selected lines.

Data Requirements​

ParameterDescriptionExpected Input
Active Line LayerA vector layer containing line features that you wish to split.A valid line layer (.shp, memory layer)
Selected FeaturesAt least one line feature must be selected from the active layer.One or more selected line features
LengthThe distance at which you want to split the line.A numeric value (entered in the spin box)
OrientationDetermines from which end the split will be measured (from the Start Point or from the End Point)."Start Point" or "End Point"
UnitsThe unit of measurement for the length (Meters, Metric Links, or Gunter's Links).Choose from the drop-down list

Workflow Summary​

  1. Input and Setup:
    Load your line layer in QGIS, select the feature(s) you wish to split, and open the Split Line Tool.
  2. Define Split Parameters:
    Specify the split length, choose the orientation (start or end of the line), and select the unit of measurement.
  3. Preview and Split:
    The tool creates a temporary point layer showing the start and end points, then uses your parameters to split the selected lines into two segments.
  4. Result and Cleanup:
    The original feature is removed, and two new features (the split segments) are added. The temporary point layer is displayed for reference, and the tool cleans up after splitting.

How to Use the Split Line Tool​

1. Launching the Tool​

  • Open the Widget:
    Access the Split Line Tool from the QGIS plugin menu or toolbar.
  • Layer Check:
    Ensure that your active layer is a valid line layer and that you have selected at least one feature.

2. Setting Up Parameters​

  • Enter Length:
    Use the numeric input (double spin box) to enter the split length. The tool accepts up to three decimal places.
  • Choose Orientation:
    Select whether the split should be measured from the “Start Point” or “End Point” using the drop-down list.
  • Select Units:
    Choose the measurement unit (Meters, Metric Links, or Gunter's Links). The tool automatically converts the value to meters for processing.

3. Executing the Split​

  • Click the Split Button:
    Press the “Split” button to perform the split operation.
  • Processing:
    The tool will create a temporary point layer to display the start and end points, then split the selected lines into two segments based on your input length.
  • Completion:
    After successful splitting, a confirmation message will be displayed. The original line is removed, and the two new segments appear on the active layer.

4. Visual Feedback​

  • Point Layer:
    A point layer named “Start and End Points” is generated to visually indicate the beginning and end of each line.
  • Categorized Symbology:
    • Green symbols represent the start points.
    • Red symbols represent the end points.

5. Cleanup​

  • Layer Removal on Close:
    When you close the widget, the temporary point layer is automatically removed from the project.

FAQs​

  1. What if no features are selected?
    • The tool requires at least one line feature to be selected. If none are selected, an error message will prompt you to select features before splitting.
  2. How do I choose the correct units?
    • The tool allows you to select from Meters, Metric Links, or Gunter's Links. Choose the unit that best matches your project’s measurement system. If in doubt, use Meters.
  3. What happens if the split length is longer than the line?
    • The tool checks that the specified split length is shorter than the overall length of the line. If not, an error will be raised.
  4. Can I see where the split will occur before executing?
    • The tool creates a temporary point layer to display the start and end points of the line, giving you a visual reference for the split.
  5. What if I want to split multiple features?
    • You can select multiple line features before launching the tool. The split operation will be applied to each selected feature individually.

Key Considerations and Best Practices​

  • Snapping and Precision:
    Ensure that your QGIS snapping settings are configured for accuracy. Adjust snapping tolerance and prioritize the active layer if you work with overlapping features.

  • Layer Management:

    • Before splitting, verify that your active layer is the correct line layer.
    • Temporarily hide or lock other layers to avoid accidental edits.

  • Saving Edits:
    Always save your project or export a backup of your layer before performing splitting operations. This helps prevent data loss if you need to revert changes.

  • Step-by-Step Approach:
    For complex geometries, consider splitting features incrementally. Review the generated segments after each split to ensure accuracy.

  • Undo/Redo:
    Use QGIS’s undo/redo functionality if you make an error. This allows you to experiment with different split lengths or orientations without permanent changes.

By following this guide, you can confidently use the Split Line Tool to manage and split your line features in QGIS, ensuring precision and enhancing your overall mapping workflow.