Geomorphometry

Geomorphometry, or geomorphometrics, is the science of quantitative land surface analysis. It gathers various mathematical, statistical and image processing techniques that can be used to quantify morphological, hydrological, ecological and other aspects of a land surface. Common synonyms for geomorphometry are geomorphological analysis, terrain morphometry or terrain analysis and land surface analysis. Geomorphometrics is the discipline based on the computational measures of the geometry, topography and shape of the Earth's horizons, and their temporal change. Geomorphometry, or geomorphometrics, is the science of quantitative land surface analysis. It gathers various mathematical, statistical and image processing techniques that can be used to quantify morphological, hydrological, ecological and other aspects of a land surface. Common synonyms for geomorphometry are geomorphological analysis, terrain morphometry or terrain analysis and land surface analysis. Geomorphometrics is the discipline based on the computational measures of the geometry, topography and shape of the Earth's horizons, and their temporal change. In simple terms, geomorphometry aims at extracting (land) surface parameters (morphometric, hydrological, climatic etc.) and objects (watersheds, stream networks, landforms etc.) using input digital land surface model (also known as digital elevation model, DEM) and parameterization software. Extracted surface parameters and objects can then be used, for example, to improve mapping and modelling of soils, vegetation, land use, geomorphological and geological features and similar. With the rapid increase of sources of DEMs today (and especially due to the Shuttle Radar Topography Mission and LIDAR-based projects), extraction of land surface parameters is becoming more and more attractive to numerous fields ranging from precision agriculture, soil-landscape modelling, climatic and hydrological applications to urban planning, education and space research. The topography of almost all Earth has been today sampled or scanned, so that DEMs are available at resolutions of 100 m or better at global scale. Land surface parameters are today successfully used for both stochastic and process-based modelling, the only remaining issue being the level of detail and vertical accuracy of the DEM. Although geomorphometry started with ideas of Brisson (1808) and Gauss (1827), the field did not evolve much until the construction of the first DEM. Geomorphology has a long history as a concept and area of study, with geomorphometry being one of the oldest related disciplines. Geomatics is a more recently evolved sub-discipline, and even more recent is the concept of geomorphometrics. This has only recently been developed since the availability of more flexible and capable geographic information system (GIS) packages, as well as higher resolution Digital Elevation Model (DEM). It is a response to the development of this GIS technology to gather and process DEM data (e.g. remote sensing, the Landsat program and photogrammetry). With a topographic landscape the question arises as to where a feature is and also as to how accurately it can be classified or identified. Geomorphometrics involves deriving values from the DEM data that infer geomorphological features, such as whether relative local values describe peaks, passes, pits, planes, channels and ridges. Due to limitations of resolution, axis-orientation, and object-definitions the derived spatial data may yield meaning with subjective observation or parameterisation, or alternatively processed as fuzzy data to handle the varying contributing errors more quantitatively – for example as a 70% overall chance of a point representing the peak of a mountain given the available data, rather than an educated guess to deal with the uncertainty. Quantitative surface analysis through geomorphometrics provides the tools for scientists and managers interested in land management. Applications areas include: As a relatively new and unknown branch of GIS the topic of geomorphometrics has few ‘famous’ pioneer figures as is the case with other fields such as hydrology (Robert Horton) or geomorphology (G. K. Gilbert). In the past geomorphometrics have been used in a wide range of studies (including some high-profile geomorphology papers by academics such as Evans, Leopold and Wolman) but it is only recently that GIS practitioners have begun to integrate it within their work. Nonetheless it is becoming increasingly used by researchers such as Andy Turner and Joseph Wood. Large institutions are increasingly developing GIS-based geomorphometric applications, one example being the creation of a Java-based software package for geomorphometrics in association with the University of Leeds.