Adding Features - Select MasterMap Feature (Polygonizer)

📝 Overview

If you’re using MasterMap with Topographic Area data, you can quickly create polygons by automatically selecting features from the MasterMap display. This “polygonizer” tool helps capture precise polygon boundaries with just a few clicks.

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🛠️ How to Select MasterMap Features (Polygonizer)

1. Enter Selection Mode

   • Click the Select Feature tool to enter selection mode.

2. Select Polygons

   • Left-click inside a polygon on the MasterMap display to select it.

   • Each left-click selects a different polygon.

   • Hold CTRL + left-click to select multiple polygons (e.g., all buildings and curtilage). 

     

   Note: Selected polygons must be contiguous to form a single polygon feature.

3. Manage Selection

   • Use the Selection Mode toggle button (left button) to enter or exit selection mode.

   • Use the Clear Feature Selection button (right button) to cancel the current selection without exiting selection mode.

   While in selection mode, zoom and pan work normally—except Zoom Area and mouse wheel scrolling are disabled.

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🏗️ Using Selected Polygons to Add a New Overlay Feature

1. Select Foreground Overlay

   • Ensure the correct overlay is set as the Foreground Overlay.

2. Select the Desired Area

   • Use the polygon selection tool (described above) to select the area you want.

3. Create the Polygon from Selection

   • Click Add | Polygon.

   • Immediately right-click anywhere and select Create from Selection from the popup menu.

   This will add a new graphic feature matching the external boundaries of the selected polygon(s).

4. Save and Add Data

   • Save the new graphic.

   • Enter overlay attribute data in the form that appears, just like with any new feature.

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📌 Important Notes

• Selected polygons must be contiguous to create a single polygon; a warning appears if the selection creates multiple polygons.

• Selecting a polygon representing land that surrounds unselected building polygons will create a polygon with holes.

• Using the Measure tool with Create from Selection shows:

  • The net area (area minus holes)

  • The perimeter, which includes all boundaries, including holes.

• Do not use the selection tool while in Edit Graphics mode if you want to edit polygons coinciding with MasterMap polygons; the selection tool will take precedence.

• You can use the selection tool in Edit Graphics mode to extend an existing polygon by adding MasterMap polygons.