This is very simple to do in Didger 5. Digitize the first polygon. Then, outline the next area as a polyline (skipping the common border with the polygon). Select both the polygon and the polyline and use the Draw | New Boundaries | Polyline to Polygon with Shared Border command.
This is very simple to do in Didger 4. Digitize the first polygon. Then, outline the next area as a polyline (skipping the common border with the polygon). Select both the polygon and the polyline and use the Tools | New Boundaries | Polyline to Polygon with Shared Border.
There are two easy ways in Didger 3 to create polygons with shared boundaries:
- The first way is to simply digitize the polygons, tracing the common boundaries exactly on top of each other when you get to them. When you are digitizing the common boundary, if you hold the CTRL key down while digitizing, Didger will snap the nodes to the nearest vertex. This way allows you to digitize the common boundaries without having to worry about tracing it exactly, and will prevent overlap. For example:
- Digitize one polygon.
- Go to Digitize | Polygon to start digitizing the second polygon. Hold the CTRL key down when you start to digitize the common boundary. When you stop digitizing the common boundary, release the CTRL key and continue digitizing the rest of the polygon. Each time you come to a shared interface, hold the CTRL key down.
- The second way is to draw polylines that define the outline of the polygons. Then you can connect the polylines together using the Tools | Connect Polylines command, and then convert the connected polyline to a polygon using the Tools | Polyline to Polygon command. For example, to draw two polygons with one common boundary follow these steps:
- Draw three polylines: one polyline for the side of one polygon, one polyline for the side of the other polygon, and the third polyline as the common boundary.
- Select the common boundary polylines and go to Edit | Replicate. Now you have two exact polylines depicting the common boundary.
- Select one of the common boundary polylines and one of the side polylines.
- Go to Tools | Connect Polylines. Then to Tools | Polyline to Polygon. This will turn that side into a polygon.
- Repeat steps 3 and 4 for the other common boundary polyline and side polyline.
Updated October 19, 2016