Terrain/Elevation

Geomorphometric variables derived from the SRTM 1 Arc-Second Global DEM at 30 m resolution, reprojected to EPSG:5072. Data is pulled from DEVISE. For complete details on data sources, processing, and metadata, please see the DEM Metrics documentation.

Multi-scale metrics are available at 5 window sizes: 90 m, 330 m, 510 m, 990 m, and 1,530 m. Single-scale metrics use a fixed 3×3 window (90 m).

Variable	Metric	Scale	Value range	Description	Source	Layers
Compound Topographic Index	cti	Single (90 m)	Unbounded; >0 accumulates water, <0 sheds water	Quantifies topographic influence on soil moisture using ln(A / tan(β)), where A is upslope contributing area and β is local slope. Higher values indicate greater potential wetness.	DEVISE	Download Selected
Heat Load Index	hli	Single (90 m)	0 (coolest) – 1 (hottest)	Estimates potential direct solar radiation based on slope and aspect using the McCune & Keon (2002) method. Accounts for the asymmetry between SW- and SE-facing slopes and corrects for slope steepness.	DEVISE	Download Selected
Topographic Position Index	tpi	Multi-scale	Unbounded; >0 ridge/hill, <0 valley/pit, ~0 mid-slope	Compares a cell's elevation to the mean elevation of its surrounding window. Positive values indicate local highs (ridges, hills); negative values indicate local lows (valleys, pits).	DEVISE	Download Selected
Terrain Ruggedness Index	tri	Multi-scale	0 (level) – ~243 m (extremely rugged)	Measures topographic heterogeneity as the root mean square of elevation differences between a focal cell and its neighbors. Ranges from level (<18.5 m) through nearly level, slightly, moderately, highly, and extremely rugged (>134 m).	DEVISE	Download Selected
Solar Radiation Aspect Index (TRASP)	trasp	Multi-scale	0 (SW-facing) – 1 (NE-facing)	Linear transformation of aspect that rescales slope orientation so that the driest (SW-facing) slopes score 0 and the wettest (NE-facing) slopes score 1, using the Roberts & Cooper (1989) method.	DEVISE	Download Selected