I need to extract some terrain parameters using the software SAGA “Relative Heights and Slope Positions”. The methodology for this tool can be found here: Böhner, J., & Selige, T. (2006). Spatial prediction of soil attributes using terrain analysis and climate regionalization. Gottinger Geographische Abhandlungen, 115, 13 -28. -28.

The relevant parts are shown in the picture.

One of the parameters “altitude above drain culmination”, symbol ADM, is calculated as in equation [04] in the figure, which involves “inverted altitude”. Does anyone know what “inverted altitude” is and what it means, and how to calculate it based on the original DEM? Thank you!