Editing features in a topology
Release 9.3 Last modified May 14, 2009	Print all topics in : "Editing topology"

About editing features in a topology

Note: This topic was updated for 9.3.1.

Editing features that participate in a topology is similar to editing simple features—in fact, you can use the same sketch tools to create new features that participate in a topology that you would use for features that do not. When you want to modify a feature that shares edges or nodes with other features in the topology, you can use the Topology Edit tool .

When editing topological features, you often have a choice of several ways of doing something. For example, suppose you manage a forest and there are two polygon feature classes, Forest and Stands, in your forest dataset. The two images below show the forest (top) and stand (bottom) polygons.

Forest polygon:



Stands polygons:



The Forest and Stands polygons are related by three topology rules: Stands must not overlap, Forest must cover Stands, and Stands must cover Forest. These rules prevent Stand polygons from overlapping, since no area can be in two stands at once. They also prevent stands from extending outside the official boundary of the whole forest or the forest boundary from covering an area not in a stand.

Suppose you are editing the Stands feature class and need to change the boundary between two of the stands. You could start editing; use the Topology Edit tool to select the shared edge; double-click the edge to edit its vertices; then add, remove, and move vertices along that edge to shape it to fit the new boundary.

You could also use the Topology Edit tool to modify edges shared by the Stands and Forest polygons. For example, suppose the actual boundary of the forest has been determined to be 150 meters east and 20 meters north of the corner where two stand features meet at the edge of the forest. You could use the Topology Edit tool to select the topology node at this intersection of features and move it to the correct location, either manually or by right-clicking the node, clicking Move, and entering the delta x,y value. The stand and forest polygons will both have their boundaries updated.

Using regular editing tools to edit features in a topology

You can also use the regular editing tools to edit individual features that participate in a topology. When you edit topologically related features using the nontopological editing tools, you are only modifying one feature at a time. If this feature shares geometry with other features, the shared geometry is not updated. If the edits create a violation of the geodatabase topology rules, you can use the Error Inspector to find the error and the Fix Topology Error tool to fix the error. There are several predefined ways that you can fix a given type of topology error. The Fix Topology Error tool allows you to right-click an error and choose which fix to use for the error.

For example, if you use the Reshape Feature task to reshape a selected polygon's border, only that feature will be updated. Since the border of the adjacent polygon was not updated at the same time, you may end up with overlapping polygons. Such an error will be discovered when you validate your topology edits. You can then use the Fix Topology Error tool to merge the error with one of the features and remove the overlap.




When the topology is validated, the overlapping area is discovered as a topology error.




The overlap is removed by applying the Merge topology error fix. The overlap is merged into feature 1, and the features 1 and 2 now are adjacent and share a border.

Using the edit sketch to make topology edits

In addition to editing topology elements with the Topology Edit tool, you can also modify and reshape a selected topology edge using an edit sketch. The Modify Edge and Reshape Edge topology edit tasks allow all features that share the edge to be updated at the same time.

The Modify Edge topology edit task takes the selected edge and makes an edit sketch from it. You can use the standard editing tools to insert, delete, or move the vertices that make up the edge. With the Reshape Edge topology edit task, you can use the basic editing tools to create a new line to replace an existing edge line.







With the Auto-Complete Polygons edit task, you can use the basic editing tools to create a new polygon that adjoins an existing polygon, using the existing polygon's geometry and the edit sketch to define the edges of the new polygon. You don't have to be editing a topology to use the Auto-Complete Polygons task.

How to edit features in a topology

Modifying an edge

1. Click the Topology Edit tool on the Topology toolbar.
   
2. Click an edge to select it.
   
3. Click the Task drop-down arrow on the Editor toolbar and click Modify Edge.
   
4. Optionally, right-click a segment of the edge that has no vertices and click Insert Vertex.
   

A new vertex is inserted into the edge and into all features that share it.

5. Optionally, right-click a vertex and click Delete Vertex.
   

The vertex is removed from the edge and from all features that share it.

6. Optionally, click a vertex and drag it to a new location.
   
7. Optionally, right-click a vertex, then click Move.
   
8. Type an x and a y distance and press Enter to move the vertex relative to its current position.
   
9. Optionally, right-click a vertex and click Move To.
   
10. Type the new coordinates for the vertex and press Enter.
    
11. Right-click anywhere on the map and click Finish Sketch.
    

Reshaping an edge

1. Click the Topology Edit tool on the Topology toolbar.
   
2. Click an edge to select it.
   
3. Click the Task drop-down arrow on the Editor toolbar and click Reshape Edge.
   
4. Click the Sketch tool on the Editor toolbar.
   
5. Start an edit sketch.
   

You can either snap the edit sketch to the selected edge or cross the edge to indicate where to start reshaping the edge.

6. Use the Sketch tools to digitize a new shape for part of the selected edge.
   

Once you've started the edit sketch, you can use any of the tools on the sketch tool palette to create your edit sketch.

You can either snap the edit sketch to the selected edge or cross the edge to indicate where to stop reshaping the edge.

7. Right-click anywhere on the map and click Finish Sketch.
   

Completing polygons using existing polygon geometry

1. Click the Task drop-down list and click Auto-Complete Polygons.
   
2. Click the target and click the polygon feature class to which you want to add polygons.
   


3. Click the Sketch tool .
   
4. Start an edit sketch.
   

Starting from the boundary of an existing polygon, use the Sketch tool to digitize a boundary of the new polygon that will share a boundary with the existing polygon.

Once you've started the edit sketch, you can use any of the tools on the sketch tool palette to create your edit sketch.

You can either snap the edit sketch to the edge of the existing polygon or start and finish the sketch just inside the existing polygon.

5. Right-click anywhere on the map and click Finish Sketch.
   

The new polygon is created from the boundary you digitized and the existing polygon's boundary.

Stretching features when editing topological elements

1. On the Editor toolbar, click the Editor menu and click Options.
   
2. Click the General tab.
   
3. Check Stretch geometry proportionately when moving a vertex.
   
4. Click OK.
   
5. Click the Topology Edit tool on the Topology toolbar.
   
6. Click a topology node or double-click a topology edge and click a vertex.
   
7. Click and drag the node or vertex to a new location.
   

The features that share the node or vertex stretch proportionately.

Snapping to topology nodes

1. On the Editor toolbar, click the Editor menu and click Snapping.
   

The Snapping Environment window appears.

2. Check Topology nodes.
   

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