Historically elevation data was collected through field surveys and later through stereo photogrammetric measurement using overlapping aerial photographs. The output was recorded as iso lines on maps with a constant equidistance (elevation difference between lines). In Denmark, our earliest national elevation data sets date back to ca 1870

List of land surface parameters derived from the Digital Elevation Model.

• Slope aspect: Direction of the steepest slope gradient from the North
• TWI : Calculates the slope gradient and specific catchment area based TWI.
  TWI = ln (As/tan β) : where As is the upslope catchment area and β is the slope gradient (Moore et al., 1993)
• Direct Sunlight Insolation (1 yr) : Calculates potential incoming solar radiation (insolation) calculated n SAGA GIS (Böhner and Antonić, 2009)
• Elevation : Lidar produced an elevation of the land surface
• Flow Accumulation: Number of upslope cells
• Mid-Slope Position : Covers the warmer zones of slopes (Bendix, 2004)
• MRVBF: Identifies the depositional areas (Gallant and Dowling, 2003)
• SAGA Wetness Index: Same as TWI but uses modified catchment area instead (Böhner et al., 2001)
• Slope gradient : Maximum rate of change between cells and neighbours.
• Slope-length factor: Calculates the slope length as used by the Universal Soil Loss Equation (Desmet and Govers, 1996)
• Vertical distance to channel network: Calculated vertical distance to the nearest channel for each cell
• Valley depth: Relative position of the valley