|Open Table of Contents||ToolBox Implementation|
|Surface curvature at a point is the
curvature of a line formed by the intersection of the surface with a plane
with a specific orientation passing through this point. The value of the
curvature is reciprocal of the radius of the curve - the larger the radius,
the smaller the curvature value (a gentle curve has small curvature and a
tight curve has large curvature value). The units of the curvature are
radians per linear unit (the unit of the spatial reference of the raster).
Because the values of the curvature are typically small, the results of the curvature functions of ET Surface are the actual curvature multiplied by 100. So the value of the curvature can be described as the change of the orientation resulting from travelling one hundred linear units along the respective line.
The sign of the curvature is assigned differently by different authors. To keep consistency with ArcGIS the functions of ET Surface assign the sign as the corresponding functions of ArcGIS. If you want to change the sign you can use the Raster Calculator to multiply the result by -1.
The functions of ET Surface calculate the curvatures for each cell of a raster dataset using its immediate neighbors as devised by Zevenbergen and Thorne (1987).
Plan Curvature is the curvature in a horizontal plane. It can be also described as the curvature of the hypothetical contour line that passes through a specific cell. The Plan Curvature is positive for cells with concave contours and negative for cells with convex contours. Plan curvature can be used to differentiate between ridges and valleys.
Profile Curvature is the curvature of the surface in the direction of the steepest slope (in the vertical plane of a flow line). The Profile Curvature affects the flow velocity of water draining the surface and influences erosion and deposition. In locations with convex(negative) Profile Curvature the erosion will prevail and in locations with concave (positive) curvature the deposition.
General Curvature (also called Total) is the curvature of the surface itself (not the curvature of a line formed by the intersection of the surface with a plane). The General Curvature can be positive or convex (indicating peaks), negative or concave (indicating valleys) or zero (indicating flat surface or a saddle).
Command line syntax
ETS_GPPlanCurvature <Input Raster> <Out Raster>
ETS_GPProfileCurvature <Input Raster> <Out Raster>
ETS_GPGeneralCurvature <Input Raster> <Out Raster>
ETS_GPPlanCurvature (Input Raster, Out_Raster)
ETS_GPProfileCurvature (Input Raster, Out_Raster)
ETS_GPGeneralCurvature (Input Raster, Out_Raster)
See the explanations above:
Zevenbergen, L.W. and Thorne, C.R. (1987) Quantitative analysis of land surface topography. Earth Surface Processes and Landforms.
Wilson, J.P., and Gallant, J.C. editors, 2000, Terrain Analysis: Principles and Applications (Chichester: Wiley).
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