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📏 Plotter Widget

Available from v2.0.0

The Plotter Widget is a crucial tool in the Gruhanaksha plugin, designed for accurately plotting points along a selected line feature. This tool is particularly useful in land surveying and FMB workflows for marking specific points like "Cut Points" and "Offset Points".

It is available as a tab within the Plotter tool.

🔧 Key Features​

  1. 📏 Flexible Unit Conversion

    • Meters
    • Metric Links (1 = 0.2 meters)
    • Gunter’s Links (1 = 0.201168 meters)
    • Feet (1 = 0.3048 meters)
    • Yards (1 = 0.9144 meters)

  2. 📍 Point Plotting

    • Cut Point: Plot a point at a specific distance along a selected line from either the start or end point.
    • Bisect Point: Plot a point at a specific distance along a selected line without any offset.
    • Offset Point: Plot a point perpendicular to the "Cut Point" at a specified offset distance.
    • Extended Point: If the "Cut Point Length" is negative or greater than the line length, it plots a point by extending the line.

  3. 🗺️ Interactive Line Segment Selection

    • Click directly on a line segment on the QGIS map canvas to select it.
    • The start (🟢) and end (🔴) points of the selected segment are automatically marked for easy reference.
    • Supports snapping for precise segment selection.

  4. 🗂️ Memory Layer Integration

    • The plotted points are added to a new or existing memory layer named "Plotted Points".
    • Points are categorized by type ("Cut Point", "Offset Point", "Extended Point") and styled for clear identification.

🚀 How to Use the Plotter Widget​

🪟 Step 1: Launch the Widget​

  1. Open QGIS.
  2. From the main tool panel, open the Plotter tool.
  3. Select the Plotter tab.

📌 Step 2: Select a Line Segment​

  1. Click the Select Segment button. The button will change to "Selecting..." and a status message will guide you.
  2. Click on a line segment on the map canvas to select it.
    • The start point will be marked in green (🟢).
    • The end point will be marked in red (🔴).

ℹ️ Use snapping for higher accuracy. You can right-click at any time to clear the segment selection.

🛠️ Step 3: Configure Inputs​

🔣 a. Units​

Choose the measurement unit for the lengths you will enter.

  • Meters
  • Metric Links
  • Gunter’s Links
  • Feet
  • Yards

👉 b. Choose Point​

Select the reference point on the line for plotting.

  • 🟢 Start Point
  • 🔴 End Point

📏 c. Lengths​

  • Cut Point Length: Enter the distance from the chosen point (start/end) along the line to place the "Cut Point".
  • Offset Length: Enter the perpendicular distance from the "Cut Point" to place the "Offset Point".

🧩 Step 4: Plot the Points​

  • Click Plot ▶️
  • The tool will calculate and plot the "Cut Point" and "Offset Point" on the "Plotted Points" memory layer.

🗺️ Step 5: Visualize the Result​

The newly created points will appear on the map, styled by their type.

🗑️ Step 6: Clear Segment​

  • Click the Clear Segment button to remove the selected segment and reset the tool for a new operation.

⚠️ Error Messages & Troubleshooting​

❗ Error Message💡 Cause✅ Solution
"Please select a segment first.""Plot" was clicked before a segment was selected.Use the "Select Segment" button to select a segment.
"Direction vector has zero length, cannot extend line."The selected segment has zero length.Select a valid segment with length.
"Line segment has zero length, cannot calculate offset."The selected segment has zero length.Select a valid segment with length.

🌟 Best Practices​

  • ✔️ Ensure your line layer has a valid CRS.
  • 📏 Double-check your units to match the project's requirements.
  • 💾 If you need to keep the generated points, right-click the "Plotted Points" memory layer and choose Export > Save Features As... to save it to a permanent file (e.g., Shapefile, GeoPackage).

📝 Example Use Case​

🗺️ Scenario: You need to mark a point 15 meters along a property line from its start, and then mark an offset point 5 meters to the left.

  1. Click Select Segment and click on the property line on the map.
  2. In the Plotter tab, set Units to Meters.
  3. Choose 🟢 Start Point.
  4. Set Cut Point Length to 15.
  5. Set Offset Length to 5.
  6. Click Plot.

🧮 Result: A "Cut Point" is created 15m from the start of the segment, and an "Offset Point" is created 5m away from the "Cut Point", perpendicular to the segment.

📌 The Plotter Widget is an essential tool for precise point creation along lines, streamlining survey and cadastral mapping workflows. 🗺️📍