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aijs = area (m2) of patch ijs within specified neighborhood (m) of patch ij. dik = similarity between patch types i and k. hijs = distance (m) between patch ijs and patch ijs, based on patch edge-to-edge distance, computed from cell center to cell center. |
| Description | SIMI equals the sum, over all neighboring patches with edges within a specified distance (m) of the focal patch, of neighboring patch area (m2) times a similarity coefficient between the focal patch type and the class of the neighboring patch (0-1), divided by the nearest edge-to-edge distance squared (m2) between the focal patch and the neighboring patch. Note, when the search buffer extends beyond the landscape boundary, only patches contained within the landscape are considered in the computations. In addition, note that the edge-to-edge distances are from cell center to cell center. |
| Units | None |
| Range | SIMI ≥ 0 SIMI = 0 if all the patches within the specified neighborhood have a zero similarity coefficient. SIMI increases as the neighborhood (defined by the specified search radius) is increasingly occupied by patches with greater similarity coefficients and as those similar patches become closer and more contiguous and less fragmented in distribution. The upper limit of SIMI is affected by the search radius and minimum distance between patches. |
| Comments | Similarity index is a modification of the proximity index (see Proximity Index description), the difference being that similarity considers the size and proximity of all patches, regardless of class, whose edges are within a specified search radius of the focal patch. Like the proximity index, this index is dimensionless (i.e., has no units) and therefore the absolute value of the index has little interpretive value; instead it is used as a comparative index. |
