gvSIG-Desktop 1.12. User manual

In gvSIG, the Add geometric info tool is available when there are visible vector layers in the active View.

Icons

Icon	Description
	Add geometric info tool enabled if there are visible vector layers in the current view.
	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:

• Postion of the layer in the TOC: displays various icons such as the layer grouping icon . The last icon always indicates a vector layer.
• Name of the layer.
• Type of geometry of the layer: five types of layer geometries are supported: point, line, polygon, multipoint, and multi (which may contain any of the above).

2. Layer information writable. Indicates whether changes can be saved to the selected layer:

Icons

Icon	Mode
	Yes, changes can be saved. In this case the attributes to be added can be selected.
	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:

• Point layer:
  • X coordinate
  • Y coordinate
  • Z coordinate
• Line layer:
  • Length of the line
• Polygon layer:
  • Perimeter of the polygon
  • Area of ​​the polygon
• Multipoint Layer:
  • Number of points that make up the geometry
• Multi geometry layers: any of the above.

The geometric attribute will be associated with one type of geometry, which is identified by the icon on the left:

Icons

Icon	Geometry type
	The attribute is characteristic of point geometries.
	The attribute is characteristic of multipoint geometries.
	The attribute is characteristic of line geometries.
	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.

Icons

Icon	Option
	Add all the geometric attributes to the list.
	Add the selected geometric attributes to the list.
	Remove the selected geometric attributes from the list.
	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

1. Progress bar: percentage of process completed.
2. Show/Hide Details: show or hide the steps that have been completed.
3. Cancel: Stops the 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:

• A gvSIG project containing a view with a vector layer is loaded.
• The Add geometric information tool is loaded.
• The layer contains polygons so Area and Perimeter attributes are available.
• These two attributes are added as new fields with default names (Because of the shape encoding support the process removes accents and any occurrences of characters such as ç, Ç, ñ, Ñ).
• Click the OK button.
• Start and end the process successfully. Attributes are added as new fields in the selected vector layer.
• Click the Accept button to close the progress dialog.
• Open the layer's attribute table and move the horizontal scroll bar to the right to view the newly added attributes.

Example showing the calculated geometric information