Compression is a schematic layout algorithm that is typically used on diagrams with containers so the features in the containers are processed as junction groups.
This layout algorithm compresses the diagram features toward the middle of the diagram while trying to maintain relative positioning. It works from a distance that allows it to build junction groups that are moved as super nodes during the algorithm execution.
This algorithm is useful for networks that span thousands of miles and are otherwise difficult to view and understand in their true geographic positions—for example, in the transmission utilities industry.
The graphics below show a sample diagram before and after applying the Compression layout: 
Here is the diagram layout after applying the Compression layout.
Apply the Compression layout on an active diagram map view
When applying this layout on a network diagram, the following prerequisites must be met:
- Since this operation is transactional, edits must be saved before it is run.
- The input network diagram layer to which the layout applies must be from either a utility network or trace network in a file geodatabase or a network diagram service. When working with a utility network in an enterprise geodatabase, the input network diagram layer must be from a service.
To apply the Compression layout on an active diagram map view, do one of the following:
- On the Network Diagram tab, click the drop-down arrow on the Diagram Layouts button in the Layout group, and click the Compression layout item in the gallery.
- Load the Apply Compression Layout tool in the Geoprocessing pane.
Then, adjust the Compression layout parameters and click Run.
Note:
To apply the layout on a subset of features in the network diagram, use one of the Select Features tools (for example, Select By Rectangle, Select By Polygon, and so on) and select the diagram features before running.
Configure the Compression layout on a diagram template
To configure this layout on your diagram template, use the Add Compression Layout tool.
Compression layout parameters
The sections below clarify the Compression diagram layout main parameters.
Preserve container layout
Most of the layout algorithms work with the Preserve container layout option. This option allows controlling the algorithm execution so it executes either on the top graph of the diagram—Preserve container layout checked, or on both content and noncontent features in the diagram—Preserve container layout unchecked.
Maximum Distance for Grouping
This parameter is used to determine when neighbor junctions must be considered part of the same junction group. A junction group acts as a top container, which will be moved as a unit during the layout execution. It can contain junctions and containers. Two conditions are required to group two junctions together: they must be connected by an edge, and the distance between them must be less than the maximum value you enter. A junction group cannot be composed of two junctions (or containers) that are very close but not connected. With a very small value for Maximum Distance for Grouping, the algorithm may not perform any grouping at all.
The images below show the differences when applying the layout on the following initial diagram:
With Maximum Distance for Grouping set to 1 foot, the blue and red junctions in the middle are too far from each other and from their neighbor container to be regrouped. The algorithm compressed all the diagram features to the middle while preserving their relative distances:
With Maximum Distance for Grouping set to 3 feet, the two blue junctions are not regrouped, and the red junction and its neighbor red container are regrouped. Then, the diagram graph compression operates.
With Maximum Distance for Grouping set to 5 feet, the two blue junctions are regrouped, and the red junction and its neighbor red container are regrouped. Then, the diagram graph compression operates.
Vertex Removal Rule
This parameter specifies how vertices along diagram edges are processed. The images below show the differences when applying each type of vertex removal rule on the following initial diagram:
- All outer vertices except the first one—Any edge vertices that are within the detected junctions' groups will be maintained; edge vertices that are outside will be removed except the first (or last) outside vertex that is preserved.
- All outer vertices—Any edge vertices that are within the detected junctions' groups will be maintained, while edge vertices that are outside will be removed.
- All vertices—All vertices on all edges
will be removed from the diagram.
