3.11 Convert Points to Polygon
Level of expertise required for this Chapter: Intermediate; general Map Maker training
If you do a ground survey collecting points (‘waypoints’), which define a parcel or a plot of land, you will have to change these points to a polygon.
1. Edit > Show Selection Manager > With the Select-tool (at toolbar left) you select the points > Selection Manager window: Selection > Check that you have only these points, no areas
If there is an area selected (or a wrong point): Pick it (1, see below) > Remove from selection (2) >
2. Convert points to line: Actions (3) > Basic operations > Points to line > A line in red (i.e. selected) should be drawn, which is not closed yet
3. Draw a 'closing' line: Line-tool (at toolbar left) > Draw a line between the two end points of the previous line > Right-click > Line window: Actions > Snap to live layer > OK > Snap to live layer window: Snap to a maximum distance on screen of 10 pixels > OK
Alternatively, you can use the Edit-tool with ‘Snap vertex to nearest vertex’ option.
4. Convert line to polygon: Select-tool (at toolbar left) > Select the 2 (or more) lines, which will form the polygon > Selection Manager window: Actions > Polygon manipulation > Convert lines to polygons > Convert lines to polygons window: Snap: 0 (all others in default) > OK
If there is a polygon next to the new polygon, you better adjust the boundary: Snap-tool (at toolbar left) > Click on the new polygon very close to the boundary > Click again on the other side, read the maximum distance, it will move the boundary
5. Don’t forget to save.
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Similar to the task of converting lines to polygons, you can also convert lines of a layer to a polygon (see Chapter 3.4).
See also Annex 16.3, if you have the coordinates of a parcel from field survey in a digital format, which you like to import and form a polygon.