D2FDY2 filter

The D2FDY2 filter is a standard linear filter which works in a 5 by 1 environment. It calculates the second derivative in y-direction (d²f / dy²). The values in the matrix are:

Gain factor = 1/24 = 0.04166666

When using the D2FDY2 filter on a DEM:

• positive values in the output map mean that the terrain is concave in y-direction
• negative values mean that the terrain is convex.

To calculate concavity and convexity in both x- and y-directions you can use the LAPLACE filter.

See also:

Filter types : linear filters

Filter types: gradient or derivative filters (technical information)

Filters : user-defined linear filters