A Filter Layer in GeoUnderground is a saved query that filters a layer by attributes and shown in a different styles. Filters Layers are a powerful tool that let a user easily find specific features in a layer based on attribute. For example, a user can filter a city crime rate map to show areas with crimes rate rates over a certain value in a different color.
To create a filter layer, go to the Folder Actions menu of the layer to be filtered and click on the “Create Filter Layer" option. Then enter a name in the editable text field and hit the enter button on your keyboard.
The Filter Layer Actions menu is used to perform activities at the filter layer level. Depending on a user’s access and permissions, some actions may not be available.
To create a filter, go to the Filter Layer Actions menu and click on the “Filters" option. The layers window is expanded to a right window pane with the Filters tab displayed.
The header of the page displays Filters and the current Layer being modified in the top left corner. An “Add Filter” button is displayed to add another filter, if needed. The “Save” and “Reset” buttons at the bottom of the window are disabled. On the bottom of the window is a message to display the number of features returned from the filter. The user has to select the parameters for the filter. The following options can be modified:
- Attribute Name – When the user clicks on the Attribute Name filed, a list of available attributes is displayed. The user can either scroll through the list and select the attribute or type the attribute name into the field.
- Operand – The operand describes the relationship between the Attribute Name and the Attribute Value. A dropdown list is displayed for the user’s convenience.
- Attribute Value – The user enters the character string into the editable field.
The filter creation is complete, but on the map the filter layer cannot be distinguished from the All Features layer. The reason is that both have the same fill color. To change the fill color for the filter layer, click on the Style tab. When all changes have been completed the right window pane can be collapsed by clicking the tab with the arrow point to the left.