Topology editing is a special editing mode. When enabled, the system will build a temporary topology based on all visible 2D line and polygon layers, ensuring topological continuity between objects during editing.

Before using topology editing, you need to first enable the editing status of the corresponding 2D line and polygon layers in the Layer Manager. Then, in the Object Editing group of the Edit Data tab, open the Topology editing drop-down menu and enable Topology edit switches. Note that if there are no 2D line or polygon layers in editing status in the map, this function cannot be enabled.

Datasources in read-only status or layers that are currently invisible cannot participate in topology editing. When the map is in dynamic projection state, topology editing is also unavailable. It can only be used after turning off Dynamic Projection in the Map Properties panel.

In topology editing mode, the following dedicated tools are provided: Align Edges, Trimming, and Topology Edit Node. These three tools are only available when topology editing is enabled. In addition, when topology editing is turned on, moving topology edges and topology nodes is supported while maintaining topological continuity; when topology editing is not enabled, it is the normal moving state without maintaining topological continuity.

To help you better understand the topology editing function, the following is a brief explanation of related concepts involved:

• Topology Node: A topology node is the intersection point of geometries of all layers participating in topology editing in the map.
• Topology Edge: A topology edge is a continuous linear boundary, and one topology edge is defined by two topology nodes.
• Topology Graph: A topology graph consists of topology nodes and topology edges, representing the topology of objects in the map. When topology editing is enabled, the topology graph will be displayed on the layers within the current map extent.

  

This chapter will introduce the following contents:

• Move: Introduces how to move topology edges and topology nodes.
• Topology Edit Node: Introduces how to use the Topology Edit Node tool to move, add, and delete object nodes.
• Trimming: Introduces how to use the Trimming tool to trim topology edges.
• Align edges: Introduces trimming a topology edge to match and coincide with another edge that shares two common topology nodes.