ILWIS objects

Filters

Filters are used in the Filter operation. In ILWIS, there are four main filter types: Linear filters, Rank order filters, Majority filters, and Binary filters. Furthermore, there is a Pattern filter and a Standard deviation filter. For an explanantion on the working of these filter types and examples, see Filter types. For examples on the use of filters, see Filter : functionality.

Some 30 standard filters are predefined in the SYSTEM directory. However, the Filter : dialog box offers many possibilities to define most filters on the fly according to your wishes before applying them. This can of course also be done on the command line of the Main window. Further, your own linear filters can be created, edited and stored on disk. For more information, see Filters : user-defined filters.

Names of filters:

In ILWIS 3, object names comply with Windows long file names. Also Universal Naming Convention (UNC) paths are supported. For more information, see How to use long object names.

To create a linear filter:

You can create your own user-defined linear filter of any odd size. Easy ways to create a new linear filter is to choose Create Filter from the File menu of the Main window, or to double-click the New Filter item in the Operation-list. For more information, refer to How to create a linear filter.

To view or edit a linear filter:

The easiest way to view or edit a linear filter is double-click a filter in a Catalog: the filter will be shown in the Filter editor. You can view all linear filters, i.e. including the linear system filters; and you can edit your own user-defined linear filters. For more information, see How to edit a user-defined linear filter.

Note:

The Average filter, Majority filters, Median filters, Rank Order filters, and the Standard Deviation filter may have a user-defined size, rank or threshold. You can define these filters on the fly in the Filter : dialog box.

Technical information:

Filters which are stored on disk consist only of an ASCII object-definition file (.FIL). This file stores the name, type and size of the filter, and it may further store matrix values for linear filters, the solution table for binary filters, etc.

By viewing the properties of a filter, you can see whether it is a system filter or not, when it was last edited, object size and the description of the filter. A filter has no relations to other objects.