Aggregating zones based on main zones

You can aggregate zones based on their allocation to main zones (Managing main zones). All or all active zones, which are allocated to a main zone, are then aggregated to a new zone and all previously aggregated zones are deleted. This way, you can generate an assignment-enabled model for main zones.

Notes: At least one main zone needs to be in the network.

The aggregation generates as many new zones as there are main zones in the network. This is not the case if, in the network, there are zones which are not allocated to a main zone. These will not be aggregated and remain in the network.

1.  If required, set the zones active, which you want to aggregate, via

The selected zones are active.

2.  In the Network window, right-click the Zones button.

The Zones shortcut menu opens.

3.  Select the Aggregation of zones according to main zones entry.

The Aggregation of zones according to main zones window opens.

4.  Make the desired changes.

Element

Description

Aggregation of active zones only

If the option has been selected, only the active zones will be aggregated.

Centroid positioning for new zones

Use the centroid position of the main zone

If the option has been selected, the centroids of the main zones are used for the new zones.

Use the position calculated from the centroids of the aggregated zones

If the option has been selected, the centroids are determined based on the centroids of the aggregated zones.

Zone polygons for new zones

Note

If neither zones nor main zones have polygons, you can only select the Do not create zone polygons option.

Use the main zone polygons

If the option has been selected, the polygon of the main zone to which the aggregated zones were allocated is used for the newly created zone. If the main zone does not have a polygon or if the Aggregation of active zones only option has been selected and not all zones of a main zone are active, the polygon will be generated from the set union of the polygons of the aggregated zones.

Fusion of the polygons of aggregated zones

If the option has been selected, the polygon created by fusion of the aggregated zones is used for the newly created zone. If the aggregated zone do not have polygons, for the new zone, no polygons with be created either.

Do not create zone polygons

If the option has been selected, no polygon will be inserted for the newly created zones.

5.  Confirm with OK.

The new zones are inserted and all aggregated zones are deleted.

Notes: The new zones are numbers consecutively.

During the aggregation the following will happen:

  • In the case of demand matrices, the values or the zones to be aggregated are summed up and allocated to the new zone.
  • In the case of skim matrices, the values of the zones to be aggregated are averaged. If a skim matrix is allocated to a demand segment with demand matrix, the mean value is generated according to this demand matrix. Otherwise the unweighted mean value is calculated (Calculating a main zone matrix from a zone matrix).