ReviewObject representations at multiple scales from digital elevation models

In the last decade landform classification and mapping has developed as one of the most active areas of geomorphometry. However, translation from continuous models of elevation and its derivatives (slope, aspect, and curvatures) to landform divisions (landforms and landform elements) is filtered by two important concepts: scale and object ontology. Although acknowledged as being important, these two issues have received surprisingly little attention.This contribution provides an overview and prospects of object representation from DEMs as a function of scale. Relationships between object delineation and classification or regionalization are explored, in the context of differences between general and specific geomorphometry. A review of scales issues in geomorphometry-ranging from scale effects to scale optimization techniques-is followed by an analysis of pros and cons of using cells and objects in DEM analysis. Prospects for coupling multi-scale analysis and object delineation are then discussed. Within this context, we propose discrete geomorphometry as a possible approach between general and specific geomorphometry. Discrete geomorphometry would apply to and describe land-surface divisions defined solely by the criteria of homogeneity in respect to a given land-surface parameter or a combination of several parameters. Homogeneity, in its turn, should always be relative to scale.

► We provide a critical review on object representation from digital elevation models. ► Scale and object ontology are concepts that filter translation from DEM to landforms. ► Scale optimization techniques remain a priority for future research. ► Footprints of cells have nothing to do with size and shape of landforms. ► We propose discrete geomorphometry as an approach to specific geomorphometry.