Multiscale topographic position image of the Australian continent

Digital elevation models (DEMs) reflect the morphology of landscape surfaces and attributes derived from these models, including slope, aspect, relief and topographic wetness index. DEMs have broad application in geomorphology, geology, hydrology, ecology and climatology. Here, we consider two important terrain attributes: topographic position index and topographic ruggedness. Topographic position index measures the topographic slope position of landforms. It compares the mean elevation of a specific neighbourhood area with the elevation value of a central cell. This is done for every cell or pixel in the DEM to derive the relative topographic position (e.g. upper, middle, lower landscape elements). Ruggedness refers to the roughness of the surface and is calculated as the standard deviation of elevations. Both these terrain attributes are scale dependent and will vary according to the size of the analysis window. Here, we generated a multiscale topographic position model over the Australian continent using a 3-second resolution (~90 m) DEM derived from the Shuttle Radar Topography Mission. The algorithm calculates topographic position scaled by the corresponding ruggedness across three spatial scales (window sizes): 0.2–8.1 km, 8.2–65.2 km and 65.6–147.6 km. The derived ternary image captures variations in topographic position across these spatial scales, giving a rich representation of nested landform features, with broad application to understanding geomorphological and hydrological processes, and mapping regolith and soils. Citation: Wilford, J., Basak, S. and Lindsay, J., 2020. Multiscale topographic position image of the Australian continent. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.