Browsing by Author "Van Niekerk, Adriaan"
Now showing 1 - 20 of 42
Results Per Page
Sort Options
- ItemA comparison of Geographical Information Science competency requirements(Edgar Elgar Publishers, 2012) Du Plessis H; Van Niekerk, Adriaan
- ItemA curriculum framework for Geographical Information Science (GISc) training at South African universities.(UNISA Press, 2012) Du Plessis H; Van Niekerk, Adriaan
- ItemA Floristic-Ecological Vegetation Map of the Mitchell Plateau Region (Northern Kimberley, Western Australia)(Curtin University, 2013) Mucina L; Stephenson GR; Daniel G; Van Niekerk, Adriaan; Boonzaaier I
- ItemA GIS database of tourism infrastructure in the Western Cape Province(2007) Van der Merwe JH; Ferreira SLA; Van Niekerk, Adriaan
- ItemAdvances in optical earth observation for geological mapping : a Review(CONSAS Conference, 2016) Ngcofe, Luncedo Dalithemba; Van Niekerk, AdriaanRecent increases in the availability of earth observation (EO) data and the advances made in its processing have opened up new opportunities for earth monitoring studies. This article reviews recent advances in EO, specifically in the optical domain, and comments on their potential for geological investigations. A review of the literature revealed that much work has been done on the use of multispectral to hyperspectral EO data for geological investigations, but that relatively little emphasis has been placed on the value of high spatial resolution in geological studies. From the literature it was found that geographic object based image analysis (GEOBIA) is a relatively new paradigm in remote sensing that has been shown to reduce the intra-class spectral variability in high spatial resolution imagery, thereby increasing image classification accuracies. It has been used for many applications, but relatively little research has been done on the application of GEOBIA for geological investigations. Another finding of this review is that the power of EO data increases substantially when different types of data are used (fused) together. Data fusion seizes the advantages of the capabilities of each sensor while reducing its limitations. By its nature, GEOBIA offers the ability to fuse disparate data sources and the review concludes that more research is required on the use of GEOBIA and data fusion of high resolution EO data for geological mapping.
- ItemAnts, altitude and change in the northern Cape Floristic Region(Blackwell publishing Ltd, 2006) Botes, A.; McGeoch, M. A.; Robertson, H. G.; Van Niekerk, Adriaan; Davids, H. P.; Chown, S. L.; 0000-0002-5631-0206Aim: Climate-modelling exercises have demonstrated that the Cape Floristic Region is highly sensitive to climate change and will apparently lose much of its northern limits over the next few decades. Because there is little monitoring of diversity in this area, ant assemblage structure was investigated within the main vegetation types in the Greater Cederberg Biodiversity Corridor. In particular, we sought to determine how ant assemblage structure differs between the main vegetation types, how restricted ants – and in particular the major myrmecochores – are to the major vegetation types, and which environmental variables might underlie differences in the ant assemblages and in the specificity of species to particular areas. Location: Northern Cape Floristic Region, Western Cape, South Africa. Methods: Sampling was undertaken during October 2002 and March 2003 across an altitudinal gradient ranging from sea level (Lambert’s Bay) to c. 2000 m a.s.l. (Sneeukop, Cederberg) and down again to 500 m a.s.l. (Wupperthal) in the Western Cape, South Africa. Pitfall traps were used to sample ants at 17 altitudinal bands, stretching over three vegetation types (Strandveld, Mountain Fynbos and Succulent Karoo). Biotic and abiotic environmental variables were collected at each sampling site. Generalized linear models were used to determine the relationships between species richness, density, abundance and the abundance of the major myrmecochores, and the environmental variables. Redundancy analysis was used to determine the relationship between ant assemblage structure and the environmental variables. The Indicator Value Method was used to identify characteristic ant species for each vegetation type and altitudinal site. Results: Temperature explained significant proportions of the variation in species density and abundance, and, together with area and several vegetation variables, contributed significantly to the separation of the assemblages in the major vegetation types and biomes. Four major myrmecochores were identified [Anoplolepis sp. (cf. custodiens), Anoplolepis sp. (cf. steinergroeveri), Camponotus niveosetosus, Tetramorium quadrispinosum]. The abundances of the two Anoplolepis species were related to vegetation variables, while the abundance of the other two species showed opposite relationships with temperature variables. Fourteen ant species were characteristic of certain vegetation types and altitudes. Several of these species contributed to the differences between the assemblages. Main conclusions: There are likely to be substantial and complex changes to ant assemblages as climates change in the northern Cape Floristic Region. Moreover, the importance of ants for ecosystem functioning suggests that these responses are not only likely to be a response solely to vegetation changes, but might also precipitate vegetation changes. The changes that are predicted to take place in the next 50 years in the Cape Floristic Region could be substantially exacerbated by such synergistic effects, which have major implications for long-term conservation plans. Ongoing monitoring of this transect will reveal the nature and pace of the change as it unfolds.
- ItemApplication of geospatial technology for gap analysis in tourism planning for the Western Cape(Academy of Science of South Africa, 2013) Van der Merwe, Johannes H.; Van Niekerk, AdriaanENGLISH ABSTRACT: We report on the use of modern spatial computing technology in the development of spatial tourism policy and planning in the context of a bounded resource base. We refer briefly to provincial tourism development policy, expand on the tourism marketing framework and use the express tourist preferences to determine suitability indicators or attraction features for a spatial tourism resource base, paying special attention to the conceptual foundations of attraction and the mapping of tourism potential variables. We applied the methodology to a combination of tourism products in the Western Cape Province of South Africa in an approach that involved applying the spatial multiple criteria evaluation through the weighted linear combination of spatial factor layers as images in a geographical information system. We performed an analysis of the gap between tourism potential and tourism resource provision at a spatial resolution of individual towns’ spheres of influence, as represented by Thiessen polygons. The outcome in map format demonstrates the applicability of the technique to the Western Cape. The fine-scale spatial result was analysed for its strategic planning implications. Our results are useful for entrepreneurial and regulatory planning and can be replicated in different spatial locations if the appropriate database can be constructed.
- ItemApplication of spatial resource data to assist in farmland valuation(2012-01-18) Naude S.D.; Kleynhans T.E.; Van Niekerk, Adriaan; Ellis F.; Lambrechts J.J.N.; 0000-0002-5631-0206A land transaction is generally not a recurring action for most buyers and sellers their experience and knowledge are limited for this reason the services of property agents and valuers are sometimes used just to get more information available. The condition of insufficient information and the inability to observe differences in land productivity gives rise to the undervaluation of good land and overvaluation of poor land. The advent of the Internet made access to comprehensive information sources easier for property agents and valuers whose critical time and resources can now be effectively managed through Geographic Information System (GIS) integrated workflow processes. This study aims to develop the blueprint for a farm valuation support system (FVSS) that assists valuers in their application of the comparable sales method by enabling them to do the following: (1) Rapid identification of the location of the subject property and transaction properties on an electronic map. (2) Comparison of the subject property with the transaction properties in terms of value contributing attributes that can be expressed in a spatial format mainly (a) location and (b) land resource quality factors not considered in existing valuation systems that primarily focus on residential property. An algorithm that generates an index value was developed to allow easy comparison of the land of a subject property and that of transaction properties. This index value distinguishes the proposed FVSS from other existing property valuation systems and can therefore be used by valuers as a first approximation of a property's soil suitability before doing further field work. The FVSS was successfully developed and tested primarily using data obtained in the Western Cape South Africa. © 2011 Elsevier Ltd.
- ItemAssessing the influence of DEM source on derived streamline and catchment boundary accuracy(South African Water Research Commission, 2019) Mashimbye, Zama Eric; De Clercq, Willem Petrus; Van Niekerk, AdriaanAccurate DEM-derived streamlines and catchment boundaries are essential for hydrological modelling. Due to the popularity of hydrological parameters derived mainly from free DEMs, it is essential to investigate the accuracy of these parameters. This study compared the spatial accuracy of streamlines and catchment boundaries derived from available digital elevation models in South Africa. Two versions of Stellenbosch University DEMs (SUDEM5 and DEMSA2), the second version of the 30 m advanced spaceborne thermal emission and reflection radiometer global digital elevation model (ASTER GDEM2), the 30 and 90 m shuttle radar topography mission (SRTM30 and SRTM90 DEM), and the 90 m Water Research Commission DEM (WRC DEM) were considered. As a reference, a 1 m GEOEYE DEM was generated from GeoEye stereo images. Catchment boundaries and streamlines were extracted from the DEMs using the Arc Hydro module. A reference catchment boundary was generated from the GEOEYE DEM and verified during field visits. Reference streamlines were digitised at a scale of 1:10 000 from the 1 m orthorectified GeoEye images. Visual inspection, as well as quantitative measures such as correctness index, mean absolute error, root mean squares error and figure of merit index were used to validate the results. The study affirmed that high resolution (<30 m) DEMs produce more accurate parameters and that DEM source and resampling techniques also play a role. However, if high resolution DEMs are not available, the 30 m SRTM DEM is recommended as its vertical accuracy was relatively high and the quality of the streamlines and catchment boundary was good. In addition, it was found that the novel Euclidean distance-based MAE and RMSE proposed in this study to compare reference and DEM-extracted raster datasets of different resolutions is a more reliable indicator of geometrical accuracy than the correctness and figure of merit indices.
- ItemAutomated wetland classification using OBIA: Agulhas Plain, South Africa.(2012) Pauw T; Van Niekerk, Adriaan
- ItemBiomass estimation using satellite imagery(2011) Van Niekerk, Adriaan; Stephenson GR
- ItemClimate and the evolution of group-living behaviour in the armadillo lizard (Ouroborus cataphractus)(ZOOLOGICAL SOC SOUTHERN AFRICA, AFRICAN ZOOLOGY CIRCULATION OFFICE, PO BOX11663,, PRETORIA, SOUTH AFRICA,0028, 2013) Shuttleworth C; Mouton PLN; Van Niekerk, Adriaan
- ItemCLUES : a web-based land use expert system for the Western Cape(Stellenbosch : Stellenbosch University, 2008-12) Van Niekerk, Adriaan; Van der Merwe, J. H.; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Geography and Environmental Studies.GIS has revolutionized geographic analysis and spatial decision support and has greatly enhanced our understanding of the real world though it’s mapping and spatial modelling capabilities. Although GIS software is becoming more powerful, less expensive and more userfriendly, GIS still remains the domain of a selected few who can operate and afford these systems. Since the introduction of web mapping tools such as Google Earth, accessibility to geographic information has escalated. Such tools enable anyone with access to a computer and the Internet to explore geographic data online and produce maps on demand. Web mapping products have, however, a very narrow range of functionality. In contrast to GIS that focuses on spatial data capture, storage, manipulation, analysis and presentation, the function of web mapping tools is to visualize and communicate geographical data. The positive impact of web mapping tools suggests, however, that GIS has not yet developed to a level where anyone can use the technology to support spatial decisions and enhance productivity. A possible solution is to close the functional gap between web mapping tools and GIS to make spatial analysis more accessible, thereby promoting geographical awareness and supporting better spatial decisions.
- ItemA comparison of land unit delineation techniques for land evaluation in the Western Cape, South Africa(Elsevier, 2010-07) Van Niekerk, Adriaan; 0000-0002-5631-0206Land 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.
- ItemDevelopment of a composite soil degradation assessment index for cocoa agroecosystems in southwestern Nigeria(European Geosciences Union, 2017-08-09) Adeniyi, Sunday Adenrele; De Clercq, Willem Petrus; Van Niekerk, AdriaanCocoa agroecosystems are a major land-use type in the tropical rainforest belt of West Africa, reportedly associated with several ecological changes, including soil degradation. This study aims to develop a composite soil degradation assessment index (CSDI) for determining the degradation level of cocoa soils under smallholder agroecosystems of southwestern Nigeria. Plots where natural forests have been converted to cocoa agroecosystems of ages 1–10, 11–40, and 41–80 years, respectively representing young cocoa plantations (YCPs), mature cocoa plantations (MCPs), and senescent cocoa plantations (SCPs), were identified to represent the biological cycle of the cocoa tree. Soil samples were collected at a depth of 0 to 20 cm in each plot and analysed in terms of their physical, chemical, and biological properties. Factor analysis of soil data revealed four major interacting soil degradation processes: decline in soil nutrients, loss of soil organic matter, increase in soil acidity, and the breakdown of soil textural characteristics over time. These processes were represented by eight soil properties (extractable zinc, silt, soil organic matter (SOM), cation exchange capacity (CEC), available phosphorus, total porosity, pH, and clay content). These soil properties were subjected to forward stepwise discriminant analysis (STEPDA), and the result showed that four soil properties (extractable zinc, cation exchange capacity, SOM, and clay content) are the most useful in separating the studied soils into YCP, MCP, and SCP. In this way, we have sufficiently eliminated redundancy in the final selection of soil degradation indicators. Based on these four soil parameters, a CSDI was developed and used to classify selected cocoa soils into three different classes of degradation. The results revealed that 65 % of the selected cocoa farms are moderately degraded, while 18 % have a high degradation status. The numerical value of the CSDI as an objective index of soil degradation under cocoa agroecosystems was statistically validated. The results of this study reveal that soil management should promote activities that help to increase organic matter and reduce Zn deficiency over the cocoa growth cycle. Finally, the newly developed CSDI can provide an early warning of soil degradation processes and help farmers and extension officers to implement rehabilitation practices on degraded cocoa soils.
- ItemDie ontwikkeling van geografiese inligtingstelsels vir omgewingsbestuur in die Wes-Kaap(Stellenbosch : Stellenbosch University, 1996) Van Niekerk, Adriaan; Stellenbosch University. Faculty of . Dept. of .
- ItemEvolution of flora and vegetation in saline habitats of South Africa(2007) Mucina L; Jurenka R; Steffen S; Van Niekerk, Adriaan
- ItemGame, fences and motor vehicle accidents : spatial patterns in the Eastern Cape(South African Wildlife Management Association, 2005-10) Eloff, P. J.; Van Niekerk, Adriaan; 0000-0002-5631-0206In South Africa, very little research on motor vehicle accidents involving animals has been done. Transport networks expand while traffic volumes and speed increases. Animals entering the road reserve pose dangers to vehicles. In the Eastern Cape, the presence of an abundance of kudu creates hazardous driving conditions for motorists. For collision prevention and the establishment of public awareness programmes, it is imperative to identify hazardous sections. In this study road traffic collision reports of a chosen route in the Eastern Cape were analysed. It was determined that the presence of long stretches of game proof fences partially clustered the spatial distribution of collision sites. Road trajectories with few or no game proof fences displayed a random distribution of collision sites. “Hotspots” were identified on which traffic authorities can focus mitigating and preventative measures.
- ItemGrowth potential study 2014(Western Cape Government, 2014-03) Van Niekerk, Adriaan; Du Plessis, Danie; Spocter, Manfred; Ferreira, Sanette; Dondaldson, Ronnie; Loots, Lieb; Boonzaaier, Ilze; Janeke, Dudley; Terhoven, QuintonThis study determined the growth potential and socio-economic needs of settlements in the Western Cape outside of the Cape Town metropolitan area using quantitative data (e.g. factors relating to socio-economic, economic, physical-environmental, infrastructure and institutional aspects). The results of the quantitative analyses were combined with qualitative information (e.g. stakeholder engagements) to identify potential interventions that might unlock latent potential within settlements and regions.
- ItemHabitat-level Classification of the Albany Coastal, Pondoland Scarp and Eastern Scarp Forests(2007) Mucina L; Pienaar E; Van Niekerk, Adriaan; Lötter MC
- «
- 1 (current)
- 2
- 3
- »