The next step is to select and parameterize the patch, class, and landscape metrics. Note, these options are only consequential if you select the respective levels in the Analysis Parameters dialog box (Fig. 5). The metrics are selected and parameterized (as needed) in the right pane of the model dialog (Fig. 3). Note, there is a separate set of tabbed dialogs for each level of metrics (patch, class, and landscape). Each dialog box consists of a series of tabbed pages. Each tabbed page represents a group of related metrics as discussed in the Background documentation.
The selection of metrics is relatively straightforward. On each tabbed page select the desired individual metrics using the check boxes, or select all of the metrics using the Select All button. You can also De-select All or Invert your selection using the corresponding buttons. Clicking on the button now will deselect all metrics. Each metric is discussed in detail in the FRAGSTATS Metrics documentation.
A number of metrics require you to provide additional parameters before they can be calculated. In most cases this involves entering a number in a text box, while in other cases, this involves specifying a separate table. These special requirements are described below in association with the corresponding tabbed page.
- Area-Edge -- If you select Total Edge (TE) or Edge Density (ED) on the Area & Edge tab at either the class or landscape level, you must also specify how you want to treat boundary and background edges (Fig. 1); specifically, what percentage of the landscape boundary and background class edges to treat as true edge and therefore included in the edge length calculations? Note, if a border is present, then only background edges are affected by this designation, since all other edges along the landscape boundary will be made explicit by the information in the border. If a border is absent, then all boundary and background edges are affected. See the Overview section for a more detailed discussion. There are three options to choose from by clicking on the select button (...):
- None - Do not count any boundary/background as edge (0%). This is the default.
- All - Count all boundary/background as edge (100%).
- Partial - Specify the percentage of boundary/background edge to treat as an edge (0-100%). For example, if you specify 50%, then half the total length of edge of involving the landscape boundary (if a border is absent) and any internal background will be included as edge in the affected metrics.
- Core area -- If you select any of the core area metrics on the Core area tab, you must also either specify a fixed edge depth (in meters) or specify an edge depth table as described previously (see Specifying Common Tables).
- Contrast -- If you select any of the contrast metrics on the Contrast tab, you must also specify an edge contrast table as described previously (see Specifying Common Tables).
- Aggregation -- If you select Proximity index (PROX) or Similarity index (SIMI) on the Aggregation tab at either the class or landscape level, you must also specify a search radius (i.e., the distance [in meters] from a focal patch within which neighboring patches are evaluated). There is no default value, so if you fail to enter a distance, an error message will be written to the Activity log window upon execution and the run will fail. In addition, if you select the Similarity index, you must also specify a similarity weights file as described previously (see Specifying Common Tables).
Likewise, if you select the Connectance index (CONNECT) at either the class or landscape level, you must also specify a threshold distance (i.e., the distance [in meters] between patches below which they are deemed connected). There is no default value, so if you fail to enter a distance, an error message will be written to the Activity log window upon execution and the run will fail.
- Diversity -- If you select Relative patch richness (RPR) on the Diversity tab at the landscape level, you must also specify the maximum number of classes. There is no default value, so if you fail to enter a distance, an error message will be written to the Activity log window upon execution and the run will fail.