Fig. 4

Normalised difference maps. Normalised difference maps represented as Δ surface, for each geomorphometric variable derived from 3DEP-1 minus MERIT-DEM. To compare the geomorphometric variables under the same scale unit, the difference has been scaled from -1 to 1 (minimum and maximum stretching) keeping the 0 value (no difference) at the 0 position. The bottom plot reports the normalised difference as mean (blue line) and standard deviation values (orange vertical lines) of the maps. The mean and standard deviation plot helps to identify which geomorphometric variables are more sensitive to variation in the DEMs (e.g. high sensitivity for variables derived from slope and aspect). The coordinates u in Equi7 are expressed in metres and refer to a study area of 18.4 × 20 km, which has a high level of forest cover, and is located in Alberta, Canada, close to Jasper National Park - image centre 118.25°W 53.29°N.