Surface roughness processing
Surface roughness statistics were calculated using the QuiP MATLAB software package. Users can download all data via the Download Centre. Data were processed as follows:
1. Surface roughness statistics were calculated on the raw profile and are provided in the "one scale" columns (NOTE: correlation length is calculated from the experimental Autocorrelation function)
2. In the cases where multi-scale roughness was observed, spectral analysis was performed to separate the high (microscopic) from the low frequency roughness. All statistics are provided in the "two scale" columns, together with the frequency K (in radians/meter) used to separate the high from the low frequency component of the roughness spectrum by Fourier transform.
3. In the case where a periodic structure was observed, a mathematical function was fitted to model the variation in local incidence angle due to the periodic structure. The average, minimum and maximum of the values of the function parameters for each paddock were derived from the experimental profiles.
Example of function to model periodic structure