A comparison of land unit delineation techniques for land evaluation in the Western Cape, South Africa

Abstract

Land evaluation, an integral part of land use planning, has been established as one of the preferred methods to support sustainable land use management. In essence, land evaluation aims to compare and match each potential land use with the properties of individual parcels of land, also called land units. A land unit is an area that is, according to predetermined properties, different from the surrounding land and can be assumed to have homogeneous land properties (e.g. climate, soils, cover). Land components (also called landform elements, terrain units or land surface segments) are often used as land units, mainly because their boundaries frequently coincide with transitions in environmental conditions. Although land components have traditionally been delineated by studying topographical maps, interpreting aerial photographs and making field measurements, such manual mapping techniques are very time-consuming and subjective. Land component maps can be generated more objectively and faster by using computer algorithms. This paper compares the maps produced by three algorithms, namely the automated land component mapper (ALCoM), the iterative self-organizing data analysis technique algorithm (ISODATA) and multi-resolution image segmentation (MRS), to determine which technique produces the most homogenous and morphologically-representative land components for an area in the Western Cape province of South Africa. The results revealed that the three methods produced significantly different land component maps. While ISODATA's units were relatively homogenous, their boundaries rarely followed morphological discontinuities. ALCoM performed better in delineating land components along terrain discontinuities, but produced relatively heterogeneous land components. Overall, MRS performed consistently well and was significantly more sensitive to morphological discontinuities than the other two methods tested. Land use managers should, however, use MRS with care as more research is needed to determine what effect its different input parameters have on land unit boundaries.

Suitability of spaceborne digital elevation models of different scales in topographic analysis: an example from Kerala, India

“…Topographic information was conventionally gathered from maps of varying scales, which has restricted their applications in geomorphology and hydrology due to tiresome, biased, labor-intensive and expensive processes of data collection (Speight 1977;Dragut and Blaschke 2006;van Niekerk 2010). On the contrary, in recent years, digital elevation model (DEM) has been widely used for 3D representation of topography and derivation of various topographic attributes in terrain analysis (Pike 2000;Wilson and Gallant 2000;Oguchi et al 2003;Masoud and Koike 2011;Romstad and Etzelmuller 2012), soil and vegetation mapping (Horsch 2003;Dobos and Hengl 2009;Jelaska 2009;Cavazzi et al 2013), mapping and modelling of natural hazards (Huggel et al 2008;Gruber et al 2009;Demirkesen 2012), hydraulic, hydrologic and geomorphologic modelling (Tarboton et al 1992;Hancock et al 2006;Peckham 2009;Gichamo et al 2012;Wang et al 2012;Schwanghart et al 2013; Barnes et al 2014), watershed modelling and erosion assessment Valeriano et al 2006;Park et al 2011;Kinsey-Henderson and Wilkinson 2013), morphometric analysis (Ozdemir and Bird 2009;Guth 2011;Thomas et al 2012) and stream assessment (Vocal Ferencevic and Ashmore 2012).…”

Determining the suitability trends for settlement based on multi criteria in Kirkuk, Iraq

“…The soil appropriateness result will provide some information or guideline for the sole use. It was stated that soil evaluation is also an integral part of soil use planning to ensure continuous soil management [27]. Soil use of the settlement zone should be harmonious with the soil supporting ability [23,24].…”

Object-based symmetric difference for land surface segmentation scale parameter optimisation

“…Even though the pixel-based delimitation of landform components are well established (Evans, 2012), the segmentation of continuous terrain through object-orientated segmentation has received much attention in recently published literature (Drăguţ and Blaschke, 2008;Eisank et al, 2014Eisank et al, , 2011Van Niekerk, 2010). This can, at least partly, be ascribed to the presence of the salt-and-pepper effect in pixel-based approaches, which compromises landform component homogeneity (Blaschke, 2010;Gao et al, 2011).…”