Go to the menu PROJECT MANAGEMENT → RULES.
New
Layer: type the name of the rule
layer and click on the icon
.
The new rule enter in the Layer list at the left.
Operation: select a spatial operation among the ones available: intersection, difference or union. See details on each operation next in this chapter.
Click on the Add Rule button to create the rule. The rule will be added to the Rules list.
Cell Column: inform the column that has the cell information (find more about cells at page Error: Reference source not found). It is possible to create rules without cell columns, however, this will affect the processing performance depending on the amount of data and users in the concurrent activity.
Note: The Cell Column field is disabled when the rule layer is defined as a destination layer.
The Intersection rule results in the area that is common to the edited polygons and the ones that already exist in the rule layer.
Note: Applications: this rule is used when it is necessary to limit the editable area or to insert in the output layer values that are found in other layers. For example, if there is a column in layer A that must be inserted in the data before it is stored in the output layer, then an intersection rule with A layer will be required (Error: Reference source not found, page Error: Reference source not found).
Rule Name: type in a name for the rule to be created. In this example, a name identifying easily that the rule is related to an intersection with SOME_DATA layer was selected. This method facilitates the following procedures to associate rules with projects. However, the selection is up to the user.
Operation: select the Intersection operation.
Layer Name: select the rule layer to define the input geometries.
Cell Column: inform which layer column was chosen to contain the cell information. It is possible to keep this field empty, however, this may affect the processing performance depending on the data quantity and users in the concurrent activity.
The difference rule removes from the edition layer the areas of intersection with the rule layer before storing the result in the destination layer.
This prevents the existence of overlaid areas. The figure below shows a blue cloud polygon that already exists in the rule layer. A new polygon, green, was drawn in the edition layer and the classification process eliminated the overlaid area. The red polygon is the one that was stored in the output layer.
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Note: The main use of this rule is to prevent the existence of overlaid areas (obtained by a difference rule where the rule layer is the same as the destination layer). However, there are many ways of using it. For example. It can be used to prevent users from classifying polygons on forbidden areas, according to the project.
A union type rule is used when it is necessary to allow the user to unite existing data of a layer.
Click on the Add Rule button to create a rule.
The Cell Column field is disabled when the selected layer is defined as an output layer, even if it is not active in any project. If it is necessary to change the cell column of an output layer, use the Define Output Layer interface, accessed by the Rules Control.