Patchanalysis指数简单对译.docx

1、Patchanalysis指数简单对译Metric Definitions (from McGarigal and Marks, 1994 and McGarigal and Marks, 1995)Class Area (CA) Sum of areas of all patches belonging to a given class. Example: Conifer Class Area (CA) = 359047.844+.+65819.984 CA = 69.6626 hectares If the map units are not specified (i.e., Data F

2、rame properties; see Set map units) and State areas in Hectares has not been selected in the Advanced Options of the Spatial Statistics dialog box, then the resulting statistics will be reported in native map units (vector layers (themes) only). In the example; CA = 696626.012 (map units). This is t

3、he case for most statistics. Landscape Area (TLA) Sum of areas of all patches in the landscape. Example: Landscape Area (TLA) = 46872.719 + 359047.844 +. + 62423.574 TLA = 184.11 hectares Percentage of Landscape (ZLAND)When analyzing by class, ZLAND is the percentage of the total landscape made up o

4、f the corresponding class (patch type). Number of Patches (NumP) Total number of patches in the landscape if Analyze by Landscape is selected, or Number of Patches for each individual class, if Analyze by Class is selected. Example: Class Level: Number of Patches (NumP) Mixedwood = 5, Conifer = 4, D

5、eciduous = 5 Landscape Level: Number of Patches (NumP) = 14 Patch Richness (PR)PR is the number of different patch types within the landcapes boundary. Patch Richness Density (PRD)PRD is equal to PR divided by the total area of the landscape (metres squared) multiplied by 10,000 and then 100 (to con

6、vert to hundreds of hectares). Largest Patch Index (LPI)The LPI is equal to the percent of the total landscape that is made up by the largest patch. When the entire landscape is made up of a single patch, the LPI will equal 100. As the size of the largest patch decreases, the LPI approaches 0. Mean

7、Patch Size (MPS) Average patch size. Example: Mean Patch Size of Conifer Patches (Class Level) MPS = (359047.844 + 139531.484 .+ 65819.984)/4 MPS = 17.42 hectares Example: Mean Patch Size of Patches (Landscape Level) MPS = (46872.719 + 359047.844 + . + 62432.574)/14 MPS = 13.15 hectares Median Patch

8、 Size (MedPS) The middle patch size, or 50th percentile. Example: Median Patch size of Conifer Patches (Class Level) MedPS = 13.22 hectares Example: Median Patch size of all patches (Landscape Level) MedPS = 7.59 hectares Patch Size Standard Deviation (PSSD) Standard Deviation of patch areas. Exampl

9、e: Patch Size Standard Deviation of Conifer Patches (Class Level) PSSD = 11.05 hectares Example: Patch Size Standard Deviation of all patches (Landscape Level) PSSD = 9.51 hectares Patch Size Coefficient of Variance (PSCoV) Coefficient of variation of patches. Example: Coefficient of Variation of Co

10、nifer patches (Class Level) PSCoV = PSSD/MPS = (11.05 hectares / 17.42 hectares) *100 = 63 Example: Coefficient of Variation of all patches (Landscape Level) PSCoV = (9.51 hectares / 13.15 hectares)*100 =72 Total Edge (TE) Perimeter of patches. Example: Total Edge Conifer (Class Level) TE = Sum of p

11、erimeter of all conifer patches. TE = 10858.88 metres Units are expressed in native maps units. Example: Total Edge all patches (Landscape Level) TE = Sum of perimeter of all patches TE = 28607.27 metres ImportantIn the case of vector layers (themes), edge calculations include all the edge on the la

12、ndscape including boundary edge. The contrasted weighted edge feature allows edge weight at the boundaries to be set to zero. In the case of raster (grid) layers (themes), edge calculations do not include the edges that surround the landscape boundary edge or any interior edges that include pixels c

13、lassified as No Data. Edge Density (ED) Amount of edge relative to the landscape area. Example: Edge Density Conifer (Class Level) ED = TE / TLA ED = 10858.88 metres/184.11 hectares = 58.98 metres/hectare Example: Edge Density of all Patches (Landscape Level) ED = 28607.27 metres/184.11 hectares = 1

14、55.38 metres/hectare Mean Patch Edge (MPE) Average amount of edge per patch. Example: Mean Patch Edge Conifer (Class Level) MPE = TE / NumP MPE = 10858.88 metres/4 patches = 2714.72 metres/patch Example: Mean Patch Edge all Patches (Landscape Level) MPE = TE / NumP MPE = 28607.27 metres/14 patches =

15、 2043.38 metres/patch Contrasted Weighted Edge Density (CWED)CWED is a measure of density of edge in a landscape (metres per hectare) with a user-specified contrast weight. CWED is equal to 0 when there is no edge in the landscape, in other words the whole landscape and its border are made up of a s

16、ingle patch. Its value increases as the amount of edge in the landscape increases and/or as the user increases the contrast weight. Landscape Shape Index (LSI) LSI is the total landscape boundary and all edge within the boundary divided by the square root of the total landscape area (square metres)

17、and adjusted by a constant (circular standard for vector layers, square standard for rasters). The LSI will increase with increasing landscape shape irregularity or increasing amounts of edge within the landscape. Double Log Fractal Dimension (DLFD)DLFD is a measure of patch perimeter complexity. It

18、 nears 1 when patch shapes are simple, such as circles or squares and it approaches 2 as patch shape perimeter complexity increases. Mean Perimeter-Area Ratio (MPAR) Shape Complexity. Example: Mean perimeter-area ratio Conifer (Class Level) MPAR = Sum of each patches perimeter/area ratio divided by

19、number of patches. MPAR = (132 m/ha + 112 m/ha + 201 m/ha + 84 m/ha)/4 patches MPAR = 182 metres/hectare Example: Mean perimeter-area ratio all patches (Landscape Level) MPAR = (200 m/ha + 132 m/ha + . + 175 m/ha)/14 patches MPAR = 185 metres/hectare Mean Shape Index (MSI) Shape Complexity. MSI is e

20、qual to 1 when all patches are circular (for polygons) or square (for rasters (grids) and it increases with increasing patch shape irregularity. MSI = sum of each patchs perimeter divided by the square root of patch area (in hectares) for each class (when analyzing by class) or all patches (when ana

21、lyzing by landscape), and adjusted for circular standard ( for polygons), or square standard (for rasters (grids), divided by the number of patches. Area Weighted Mean Shape Index (AWMSI)AWMSI is equal to 1 when all patches are circular (for polygons) or square (for rasters (grids) and it increases

22、with increasing patch shape irregularity. AWMSI equals the sum of each patchs perimeter, divided by the square root of patch area (in hectares) for each class (when analyzing by class) or for all patches (when analyzing by landscape), and adjusted for circular standard ( for polygons), or square sta

23、ndard (for rasters (grids), divided by the number of patches. It differs from the MSI in that its weighted by patch area so larger patches will weigh more than smaller ones. Mean Patch Fractal Dimension (MPFD) Shape Complexity. Mean patch fractal dimension (MPFD) is another measure of shape complexi

24、ty. Mean fractal dimension approaches one for shapes with simple perimeters and approaches two when shapes are more complex. Area Weighted Mean Patch Fractal Dimension (AWMPFD) Shape Complexity adjusted for shape size. Area weighted mean patch fractal dimension is the same as mean patch fractal dime

25、nsion with the addition of individual patch area weighting applied to each patch. Because larger patches tend to be more complex than smaller patches, this has the effect of determining patch complexity independent of its size. The unit of measure is the same as mean patch fractal dimension. Mean Ne

26、arest Neighbor (MNN) Measure of patch isolation. The nearest neighbor distance of an individual patch is the shortest distance to a similar patch (edge to edge). The mean nearest neighbor distance is the average of these distances (metres) for individual classes at the class level and the mean of th

27、e class nearest neighbor distances at the landscape level. Interspersion Juxtaposition Index (IJI) Measure of patch adacency. Approaches zero when the distribution of unique patch adjacencies becomes uneven and 100 when all patch types are equally adjacent. Interspersion requires that the landscape

28、be made up of a minimum of three classes. At the class level interspersion is a measure of relative interspersion of each class. At the landscape level it is a measure of the interspersion of the each patch in the landscape. Mean Proximity Index (MPI) Measure of the degree of isolation and fragmenta

29、tion. Mean proximity index is a measure of the degree of isolation and fragmentation of a patch. MPI uses the nearest neighbor statistic. The distance threshold default is 1,000,000. If MPI is required at specific distances, select Set MPI Threshold from the main Patch pull-down menu and enter a thr

30、eshold distance. Both MNN and MPI use the nearest neighbor statistic of similar polygons in their algorithm. Occasionally a blank or zero will be reported in MNN and MPI fields. This happens when one polygon vertex touches another polygons border but the two similar polygons do not share a common bo

31、rder. When this happens a manual edit (move) of the touching vertex will correct the problem in the layer (theme). This problem will not happen when analyzing raster (grid) layers (themes). Shannons Diversity Index (SDI) Measure of relative patch diversity. Shannons diversity index is only available

32、 at the landscape level and is a relative measure of patch diversity. The index will equal zero when there is only one patch in the landscape and increases as the number of patch types or proportional distribution of patch types increases. Simpsons Diversity Index (SIDI)Measure of relative patch diversity. Si