Map topology

Topological editing is an editing mode that constrains coincident geometry to an ordered graph of topologically connected edges and nodes. It requires no setup and operates only on visible features that are editable.

Located on the Edit tab in the Manage Edits group, you can turn topological editing on and off as you modify features. Map Topology operates on all features. Choosing a geodatabase topology rule limits topological editing to features participating in the selected rule.

Turning on topological editing makes the graph available to editing tools and shows an Edges tab on tools that can perform both feature and topological edits. Editing an edge or a node modifies the corresponding feature geometry; for example, moving a shared edge also stretches any connected segments.

The connectedness of your changes is validated when you Finish your edits. If they break the topological graph, the message Edit operation failed appears and your changes are canceled.

Map topology options

In Map Topology Options, the cluster tolerance determines whether edges and vertices are coincident. By default, the minimum possible cluster tolerance is automatically calculated for you. For most cases, using the default tolerance is the best practice.

Caution:

Increasing the cluster tolerance can potentially reduce the spatial accuracy of your results and cause feature to distort or collapse.

Editing tools

Editing tools that can perform topological edits are described in the following table:

Tool	Description
Align Edge	Reshape a topology edge to match and be coincident with another topology edge that shares two common topology nodes.
Edit Vertices	Make simple edits to topologically connected vertices. If map topology is turned on, you can move, delete, or add a topological vertex and preserve the connectedness of shared boundaries.
Move	Move topological edges or features. If map topology is turned on, all features that are connected to the selected edge stretch and move to maintain connectivity. You can move the selection anchor and use it to snap to other features based your current snap settings.
Reshape	Reshape shared topological boundaries. If map topology is turned on, the linear shape you draw across an edge replaces existing topology edges where the first and last segment cross or touch one or more topologically connected features.
Generalize	Reduce the complexity of a line or a polygon feature while retaining its basic shape. If map topology is turned on, connectivity among all shared boundaries is preserved.

The topology graph

Topological constraints are applied by means of a topological graph. The graph appears as a highlighted network of edges and nodes over the features you are editing. Edges define shared linear boundaries, and nodes define connectivity across endpoints and intersections.

How nodes and edges correspond to feature geometry is summarized in the following table.

Map topology edges and nodes

Simple feature	Topology element
Point	Points have node behavior when they are coincident with other features in a topology.
Polyline or polygon	An edge is defined by a linear boundary. Two nodes define the endpoints of an edge. Vertices define the shape of an edge between two nodes. Nodes also define edge intersections.