Editing affects topology when it changes the relationship among the geographic features. An arc that used to meet another arc could be clipped so that they no longer meet, a new arc could be added to split a polygon in two, and an arc could be deleted to merge two polygons into one. We will investigate the effect of editing on topology in this chapter.

Highlight arcs around a node.

This is to show that the GIS has linked arcs around a node for quick retrieval.

1. Select the Edit > Topology > Cycle > Arcs Around Nodes menu item and point at this arc.

(288569, 740026), 1:1200

2. The arc will be highlighted. Click on the left mouse button to confirm.

3. The closer node will be highlighted. Click on the left mouse button to confirm.

4. The next arc linked to the same node will be highlighted.

5. Clicking the left mouse button will highlight each of the other arcs linked to this node. Click on the right mouse button to quit from this command.