General Comments

Not all groups of metrics (see previous list) have metrics at all levels. For example, diversity metrics only exist at the landscape level. Also note that the organizational hierarchy used here is opposite of that used in the FRAGSTATS graphical user interface (GUI). In the GUI, metrics are first grouped by level (patch, class, and landscape) and then further grouped by the aspect of landscape pattern measured. The GUI organization strives to be consistent with the way most users conduct a FRAGSTATS analysis. Often times, for example, users are only interested in class level metrics. Here, however, the discussion of the metrics is facilitated by reversing the hierarchy and first grouping them according the aspect of pattern measured, then by the level of organization (patch, class, and landscape). In this manner, issues common to all metrics that relate to the same aspect of landscape pattern can be discussed once.

Following this convention, each metrics section begins with a brief introduction to the metrics in the group, followed by an overview of the various metrics computed by FRAGSTATS and a discussion of important limitations in their use and interpretation. Following this overview, each metric is defined, including a mathematical definition, measurement units, theoretical range in values, and any special considerations or limitations in the use of the metric. For each metric, the mathematical formula is described in narrative terms to facilitate interpretation of the formula. The acronym for the metric given on the left-hand side of the equation is the field name used in the ASCII output files. To facilitate interpretation of the algorithm, we intentionally separate from each equation any constants used to rescale the metric. For example, in many cases the right-hand side of the equation is multiplied by 100 to convert a proportion to a percentage, or multiplied or divided by 10,000 to convert m² to hectares. These conversion factors are separated out by parentheses even though they may be factored into the equation differently in the computational form of the algorithm.