DEM Curvature Calculate

Instructions for use

Calculates the curvature of DEM Raster Data surfaces, including Mean Curvature, Profile Curvatur, and Plane Curvature. Curvature is the second derivative of a surface, or what may be called the slope of a slope. Output Result is the surface curvature of each pixel of the terrain grid. This value is obtained by fitting the pixel with eight adjacent pixels, and then calculating the curvature of the fitting surface at the position of (0,0). The result is output as a Raster Dataset, and the output curvature types are: Mean Curvature, Profile Curvatur, and Plane Curvature.

  • Mean Curvature: It refers to the average value of any two orthogonal curvatures perpendicular to each other at a point on the surface of the earth, which measures the degree of curvature of the surface of the earth in space.
  • Profile Curvatur: a measure of the rate of change of ground elevation along the direction of the maximum slope of the ground, which is the rate of change of the ground slope and reflects the characteristics of topographic relief.
  • Plane Curvature: The measurement of the ground elevation change rate in the vertical direction along the maximum slope of the ground, which is the curvature of the curve at a point on the toposurface obtained by cutting the toposurface along the horizontal direction through the horizontal plane at the point on the toposurface. It reflects the change of the surface along the horizontal direction.

The results show that:

  • The newly generated three curvature Dataset Bounds are as large as the original Dataset, and the resolution is the same as the original Dataset.
  • In the newly generated three kinds of curvature Result Dataset, the positive curvature indicates that the surface where the pixel is located is convex upward, the negative curvature indicates that the opening of the surface where the pixel is located is concave upward, and the zero curvature indicates that the surface where the pixel is located is flat.
  • Curvature grid values are output in hundredths of a z-unit. A reasonable expectation for all three output grids is between -0.5 and 0.5 for a mountainous terrain (gentle terrain) and between -4 and 4 for a steeper rugged terrain (extreme terrain). Note that some grid surfaces may exceed this range.

Function entrance

  • On the Spatial Analysis tab-> Raster Analysis-> Surface Analysis-> DEM Curvature Calculate;
  • Toolbox-> Raster Analysis Tools-> Surface Analysis-> Terrain Calculation-> DEM Curvature Calculate.

Main parameters

  • Set the source data, that is, set the Raster Dataset for the dem curvature calculation.
    • Datasource: All the Datasources in the Current Workspace are listed. Select the Datasource where the Raster Dataset for curvature calculation is located.
    • Dataset: lists all the Raster Datasets in the Current Data source. Select the curvature calculation Raster Dataset in the list. If Raster Dataset is selected in Workspace Manager, the Dataset is automatically located.
    • Elevation Scaling Factor: When calculating the curvature, the unit of the terrain grid value (i.e. elevation value) is required to be the same as the unit of the X and y coordinates. Usually, the elevation value is multiplied by an elevation scaling factor to make the three units consistent. For example, the units in the X and Y directions are meters, and the units in the Z direction are feet. Since 1 foot equals 0.3048 meters, you need to specify a scaling factor of 0.3048. If set to 1, there is no scaling.
  • Result Data is the Result Raster Dataset after the DEM Curvature Calculate.
    • Datasource: lists all Datasources in Current Workspace, and selects the Datasource to be saved by Raster Dataset after curvature calculation. Default is the same as Source Datasource.
    • Mean Curvature Dataset: Used to set the name of the Mean Curvature Raster Dataset. The default is AverageCurvature.
    • Profile CurvaturDataset: Used to set the name of the Profile CurvaturRaster Dataset. The default is Profile Curvature.
    • Plane Curvature Dataset: Used to set the name of the Mean Curvature Raster Dataset. The default is PlanCurvature.

Precautions

  1. When the conversion between the elevation value unit and the Unit cannot be adjusted by a fixed value, the data needs to be processed by other means. One of the most common cases is that when the dem grid uses the Geographic Coordinate System, the unit is degree, and the unit of the elevation value is meter. In this case, it is recommended to perform Projection Transformation on the DEM grid. Convert X, y Coordinate Transformation to plane coordinates.
  2. If the cell to be calculated has no value, the Calculate Result also has no value. However, for cells on the edge of the Raster Dataset, the 3 × 3 neighborhood contains cells outside the Dataset Bounds, which are calculated using the elevation value of the cell being calculated, so the resulting curvature may be smaller than it is. The same is true for no values in the surrounding cells.
  3. When the names of Profile CurvaturDataset and Plane CurvatureDataset are empty, the two Raster Datasets are not generated. However, the Mean CurvatureDataset must be generated with The name cannot be empty.

Related topics

About Surface Analysis