"New layer with derived geometries" tool.
This tool allows users to generate geometries derived from points or lines in a vector layer, and to store them as a new shape layer.
Icon | Description |
---|---|
Derived geometries tool enabled if the TOC contains at least one visible point or line vector layer that is not in edit mode. | |
Derived geometries tool disabled if the TOC does not contain any visible point or line vector layers that are not in edit mode. |
The tool can be accessed from:
Via the menu: Layer / Derivative geometries
Layer selection dialog and process
Upon choosing the tool a dialog for selecting layers is displayed:
Source layer geometry type | Type of process | Target layer geometry type |
---|---|---|
Points | Points to line | Lines |
Points | Points to polygon | Polygons |
Lines | Close polylines | Polygons |
Process Control Panel
The control panel is associated with the layer and is shown every time the layer is activated in the TOC, as long as the layer is visible and not in edit mode.
The dialog has a semi-modal behavior in order to allow the user to continue working with gvSIG by using the minimize, maximize, resize and hide buttons (use the X, not the Cancel button, to hide the dialog).
The results of the completed process can be viewed by clicking on the "View Details" button. There are three types of data that are of interest here:
This information is recorded in the gvSIG log.
The control panel is hidden during the process but becomes visible again when the progress dialog is closed.
Control Panel Behaviour
The control panel is linked to the source layer from the time it is created until it is cancelled by clicking the cancel button.
Action | GUI Element | Description |
---|---|---|
Maximize | Resizes the dialog so that it fills all available space. | |
Minimize | Minimizes the control panel to a restore button. | |
Collapse | Control panel is hidden but remains linked to both the source and output layers. Further operations between these layers can be performed once the panel is restored. | |
Resize | The size of the control panel can be increased or reduced by selecting and dragging the edge of the panel. | |
Expand / Collapse splitter interface | These controls are used to display only the table of source layer features, or only the table of selected features and associated management controls, or both halves of the control panel interface. | |
Cancel | Closes the tool so that is no longer available for operations between the source and output layers. |
When the control panel is hidden it can be restored it by clicking on the source layer in the TOC.
If the View is closed when control panels are visible, the panels will be hidden and then restored when the View is reopened.
Geometries derived from points do not retain any attribute values but do maintain the columns. Those derived from lines, keep all attributes.
Removing the new layer associated with control panel will result in the tool being ended and a warning being displayed to the user.
Examples
This example will show how to generate a line layer showing the path followed from home to work, and back again. The example uses the following four shape layers:
Once all four layers have been loaded the "Derived Geometries" tool can be selected and the following values entered:
When "OK" is clicked the new process control panel appears. If a file with the same name as the new output layer already exists then the user is asked whether to continue or not. If yes, then the file will be overwritten.
Minimizing the control panel will reveal the View:
The geometries can be selected from the top table in the control panel.
We select the first seven geometry points (1st route: work to home).
Click "Create" to generate the first path:
Modify the symbology so that the route stands out as a thick line.
To generate the route back, activate the control panel and select the remaining points from the source layer so that the line can be generated:
Finally suppose we are interested in the polygon formed by the closure of the routes.
Cancel the tool and then reopen it but this time use the new layer as the source:
Select all the geometries (the two polylines) and generate the polygons.
Since the layer "Route: Work to Home" does not contain data due to the points to line process, we assign a distinguishing identifier to each by editing the layer.
Now apply some changes to the symbolology: