In gvSIG, the Add geometric info tool is available when there are visible vector layers in the active View.
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Add geometric info tool enabled if there are visible vector layers in the current view. |
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Add geometric info tool disabled if there are no visible vector layers in the current view. |
With this tool you can select which geometric properties to calculate for a visible vector layer in the current view, and then save these properties in the layer itself. The information can be saved in either new or existing fields in the layer's attribute table.
Once the above condition is met (i.e. a visible vector layer in the active View), the tool is available:
Via the menu: Layer → Add geometric info
Selecting the Add geometric info tool from the menu
Selecting the tool displays a dialog where the attributes to be added can be selected:
Add geometric information
1. Drop-down list for selecting vector layers. Lists the layers in the order that they appear in the TOC of the active view. The following information is shown:
2. Layer information writable. Indicates whether changes can be saved to the selected layer:
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Yes, changes can be saved. In this case the attributes to be added can be selected. |
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No, changes can't be saved. The tool will not list any attributes. |
3. List of geometric attributes. List of attributes of the geometry of the layer. These depend on the type of layer:
The geometric attribute will be associated with one type of geometry, which is identified by the icon on the left:
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The attribute is characteristic of point geometries. |
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The attribute is characteristic of multipoint geometries. |
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The attribute is characteristic of line geometries. |
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The attribute is characteristic of polygon geometries. |
4. Selection buttons. Allow attributes to be added to, or removed from, the list of geometry attributes to be calculated and saved for the vector layer.
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Add all the geometric attributes to the list. |
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Add the selected geometric attributes to the list. |
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Remove the selected geometric attributes from the list. |
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Remove all the geometric attributes from the list. |
5. List of added geometric attributes. List of layer geometry attributes to be calculated and added.
Clicking on any of the attributes in this list enables the controls that allow the field to be renamed.
6. New field. This checkbox indicates whether the attribute is added as a new field, or as an update to an existing field in the vector layer.
By default, every attribute is added as a new field.
7. Field name. New fields can have any name. Otherwise, select a field to update.
The length of the field names is limited.
It is possible that the layer's alphanumeric encoding does not support some characters of the current language.
8. Save field settings. If the checkbox field is changed, or if another field name is specified, the changes can be saved by pressing this button.
Add geometric information
9. Reset. Resets the dialog by reloading the current View's visible vector layers, and by removing any selected attributes and their settings.
Once all the attributes have been selected, click the Ok button to start the process and display a progress bar.
Clicking the Cancel button, on the other hand, will terminate the tool.
Progress of the Add geometric information process
In the event of a serious problem, the process is terminated and an error message is displayed:
Error message
If the process completes successfully, the Accept button is enabled and the tool can be closed.
It is possible to view the steps that were performed by clicking the Show Details button in the dialog:
List of steps performed in adding geometric information
Do not use the gvSIG interface while the process is in progress as this can produce inconsistent data states, and even errors.
It should be noted that gvSIG currently adds the areas and perimeters of islands to that of the surrounding geometry.
EXAMPLE
Following the steps described in paragraph 5:
Example showing the calculated geometric information