Description Usage Arguments Details Examples
The function allows to perform landform classification on the basis of the Topographic Position Index calculated from an input Digital Terrain Model (RasterLayer class).
1 2 | landfClass(x, scale = 3, sn = 3, ln = 7, n.classes = "six",
add.tpi = FALSE, stand.tpi = FALSE)
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x: |
input DTM (RasterLayer class). |
scale: |
size (in terms of cells per side) of the neighborhood (moving window) to be used; it must be an odd integer. |
sn: |
if the 10-class classification is selected, this paramenter sets the s(mall) n(eighborhood) to be used. |
ln: |
if the 10-class classification is selected, this paramenter sets the l(arge) n(eighborhood) to be used. |
n.classes: |
"six" or "ten" for a six- or ten-class landform classification. |
add.tpi: |
set to TRUE will return a TPI raster (FALSE is default). |
stand.tpi: |
specifies whether the returned TPI raster will be un- or standardized (FALSE is default). |
The TPI is the difference between the elevation of a given cell and the average elevation of the surrounding cells in a user defined moving window.
For landform classification, the TPI is first standardized and then thresholded; to isolate certain classes, a slope raster (which is internally worked out) is also needed.
For details about the implemented classification, see: http://www.jennessent.com/downloads/tpi_documentation_online.pdf.
Two methods are available:
-the first (devised by Weiss) produces a 6-class landform classification comprising
– valley
– lower slope
– flat slope
– middle slope
– upper clope
– ridge
-the second (devised by Jennes) produces a 10-class classification comprising
– canyons, deeply incised streams
– midslope drainages, shallow valleys
– upland drainages, headwaters
– u-shaped valleys
– plains
– open slopes
– upper slopes, mesas
– local ridges, hills in valleys
– midslope ridges, small hills
– mountain tops, high ridges
The second classification is based on two TPI that make use of two neighborhoods (moving windows) of different size: a s(mall) n(eighborhood) and a l(arge) n(eighborhood),
defined by the parameters sn and ln.
Besides rasters representing the different landform classes, the function optionally returns the TPI raster, either un- or standarized.
1 2 3 | data(elev) #load the 'elev' raster from the 'raster' package
landfClass(elev, scale=5, add.tpi=TRUE, stand.tpi=TRUE) #perform the 6-class landform analysis (which is default), and also produce the standardized TPI; a moving window of dimension 5 (in terms of cells per side) is used
landfClass(elev, sn=5, ln=11, n.classes="ten") #perform the 10-class landform analysis, with a s(mall) n(eighborhood) of size 5 and a l(arge) n(eighborhood) of size 11
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