April 9, 2018
Landscape metrics quantify various aspects of a pattern and are well-suited for comparing landscapes from a focused perspective, for example, a landscape fragmentation. However they are ill-suited for an overall assessment of similarity between landscapes because it is unclear how to combine semantically different metrics into a single measure of patterns congruity.
To perform analyses based on an overall similarity between landscapes, we represent their patterns by a histogram of co-occurrence pattern features.
A co-occurrence feature is a pair of classes assigned to two neighboring raster cells. For a landscape with k classes the histogram has (k^2+k)/2 bins which together quantify composition and configuration of the pattern. Note that all bins have the same semantic meaning – they are counts of co-occurrence features – so there is no problem of how to combine them to assess an overall similarity between two landscapes. For such assessment we use the Jensen-Shannon divergence (JSD) between two co-occurrence histograms. The result is a single number between 0 (patterns are identical) and 1 (none of the classes found in one landscape is found in the other).
Similarity-based analysis allows working with patterns in large (regional, continental, global) datasets. Possible tasks include: pattern regionalization, change detection, and search. We have developed an open-source software GeoPAT 2.0 (Geospatial Pattern Analysis Toolbox), downloadable from http://sil.uc.edu/cms/index.php?id=geopat2, which performs those tasks.
Presented examples include global delineation of ecophysiographic land units (utilizes patterns of land cover, land forms, soils, and climate), global assessment of local landscape change between 1992 and 2015 (utilizes CCI-LC global land cover data), and landscape search over the US (utilizes NLCD). Landscape search is illustrated by an online interactive application (http://sil.uc.edu/webapps/landex_usa/) where user selects a landscape and the app produces a map of US indicating locations with an overall similar landscape.