You can create custom layers based on existing base themes. This is particularly useful for example if you want to create a theme (and hence a layer) which will only contain features that satisfy some custom criteria. e.g. safety fences of a specific type.

To create a custom layer:

1. Ensure you have selected Custom Theme in the Create new GIS Theme form.
2. Select an existing Base Theme Table from the dropdown list. The corresponding table will be displayed in the read- only Table Name text box. The Theme Name textbox will default to {Base Theme}_NAME. Edit this value if required.

   

3. Define the criteria you want to use for the theme by selecting an Attribute, Operator, and Value for each condition. You can define more than one attribute value; click the button on the left to add more.
4. This adds an And/Or box to allow you to define how the composite conditions behave:
   • If you use “And” all of the defined conditions must be met for datum(s) meeting the criteria to be returned by the search.
   • If you use “Or” records meeting ANY of the defined conditions will be returned.
   • You can add more attribute value filters to the search by clicking Add Group.
5. To Remove a condition, click the button next to the associated condition. To remove a group of conditions click Remove Group.

   

6. Once you are satisfied with your criteria, click Create Theme.