The ACR rugosity index is defined as the contoured (real) surface area divided by the area of the surface orthogonally projected onto a plane of best fit (POBF), where the POBF is a function (linear interpolation) of the boundary data only. Using a POBF, instead of an arbitrary horizontal geometric plane, results in an important advantage of the ACR rugosity index: unlike most rugosity indices ACR rugosity is not confounded by slope.
The ACR rugosity index is defined as the contoured (real) surface area divided by the area of the surface orthogonally projected onto a plane that best fits its boundaries, where this plane is determined through linear interpolation based on boundary data only. This approach provides an essential benefit over traditional methods: unlike most rugosity indices, ACR rugosity is not influenced by slope.