A. van Niekerk

Model-Based Integrated Methods for Quantitative Estimation of Soil Salinity from Hyperspectral Remote Sensing Data： A Case Study of Selected South African Soils

Abstract Soil salinization is a land degradation process that leads to reduced agricultural yields. This study investigated the method that can best predict electrical conductivity (EC) in dry soils using individual bands, a normalized difference salinity index (NDSI), partial least squares regression (PLSR), and bagging PLSR. Soil spectral reflectance of dried, ground, and sieved soil samples containing varying amounts of EC was measured using an ASD FieldSpec spectrometer in a darkroom. Predictive models were computed using a training dataset. An independent validation dataset was used to validate the models. The results showed that good predictions could be made based on bagging PLSR using first derivative reflectance (validation R 2 = 0.85), PLSR using untransformed reflectance (validation R 2 = 0.70), NDSI (validation R 2 = 0.65), and the untransformed individual band at 2 257 nm (validation R 2 = 0.60) predictive models. These suggested the potential of mapping soil salinity using airborne and/or satellite hyperspectral data during dry seasons.

Evaluation of a rule-based compositing technique for Landsat-5 TM and Landsat-7 ETM+ images

Abstract Image compositing is a multi-objective optimization process. Its goal is to produce a seamless cloud and artefact-free artificial image. This is achieved by aggregating image observations and by replacing poor and cloudy data with good observations from imagery acquired within the timeframe of interest. This compositing process aims to minimise the visual artefacts which could result from different radiometric properties, caused by atmospheric conditions, phenologic patterns and land cover changes. It has the following requirements: (1) image compositing must be cloud free, which requires the detection of clouds and shadows, and (2) the image composite must be seamless, minimizing artefacts and visible across inter image seams. This study proposes a new rule-based compositing technique (RBC) that combines the strengths of several existing methods. A quantitative and qualitative evaluation is made of the RBC technique by comparing it to the maximum NDVI (MaxNDVI), minimum red (MinRed) and maximum ratio (MaxRatio) compositing techniques. A total of 174 Landsat TM and ETM+ images, covering three study sites and three different timeframes for each site, are used in the evaluation. A new set of quantitative/qualitative evaluation techniques for compositing quality measurement was developed and showed that the RBC technique outperformed all other techniques, with MaxRatio, MaxNDVI, and MinRed techniques in order of performance from best to worst.

Resource-directed spatial planning of agritourism with GIS.

This article shows how modern spatial computing technology can be used for the development of spatial policy and planning of agritourism. An application is performed in the Western Cape province of South Africa. The article overviews provincial tourism development policy, the tourism marketing framework and the expressed tourist preferences that translate into spatial suitability indicators or attraction features captured in the agritourism resource base. Special attention is given to the conceptual foundations of what defines attraction and which can be captured in a spatial format as mapped variables. The methodological approach of spatial multiple criteria evaluation is applied through weighted linear combination of spatial factor layers as images in a geographical information system. The outcome in map format demonstrates the applicability of the technique to the Western Cape. The finely detailed spatial result is compared with coarser regional indicators from a spatial development framework proposed for guiding official tourism planning. The entrepreneurial implications of the analyses are indicated. The results are useful for entrepreneurial and regulatory planning that can be replicated in different spatial locations if the appropriate database can be constructed.

A curriculum framework for Geographical Information Science (GISc) training at South African universities.

Geographical information science (GISc) is one of the fastest growing industries worldwide. Being a relatively new discipline, universities often provide training as part of geography, surveying, town planning, environmental and computer science programmes. This complicates professional accreditation assessments as the content, outcomes, extent and quality of training can vary significantly. In this paper one international and two South African GISc curriculum development models are qualitatively compared. Results show that, although there is significant intersection between the three models, some characteristics are unique to specific models. A new framework consisting of 15 components and compatible with international curricula is proposed. It addresses the needs of the South African industry while meeting the requirements of the South African GISc professional registration body. It is furthermore useful for comparing curricula and can support general curriculum design. Keywords curriculum development; geographical information science (GISc); geomatics; geographical information systems (GIS); training; programme accreditation

Medical futility and end-of-life care

Acceptance of the concept of medical futility facilitates a paradigm shift from curative to palliative medicine, accommodating a more humane approach and avoiding unnecessary suffering in the course of the dying process. This should not be looked upon as abandoning the patient but rather as providing the patient and family with an opportunity to come to terms with the dying process. It also does not entail withdrawal or passivity on the part of the health care professional. In addition to medical skills, the treating physician is responsible for guiding this process by demonstrating sensitivity and compassion, respecting the values of patients, their families and the medical staff. The need for training to equip medical staff to take responsibility as empathetic participants in end-of-life decision-making is underscored.

Iatrogenic HIV transmission in South Africa: Evidence, estimates and moral perspectives

The risks of HIV transmission to patients exceed many health professionals’ expectations in South Africa. Non-vertical HIV transmission to children is more common in cases where adherence to infection control guidelines is generally poor.

Politico-philosophical perspectives on reconciliation

The article is an analysis of the philosophical meaning and political prospects of the idea of reconciliation between all South Africans. The author is sceptical about this prospect. While he regards reconciliation as an admirable theological doctrine, he doubts whether it is easily translatable into socio-political practice in South Africa. The settlement reached in the aftermath of apartheid is not primarily to be explicated in terms of a model of reconciliation where people forgive and learn to like one another, but rather in terms of the Hobbesian model of a “war of all against all”, redeemed by the restoration of basic values. The author analyses a variety of conceptions of reconciliation that were developed in the aftermath of the Truth and Reconciliation Commission process. In South Africa, the emphasis should be on the “concilium” aspect of reconciliation, i.e. the (re-) constitution of an assembly for social, political and economic deliberation. A general commitment of all South Africans to the values embedded in the South African constitution holds far more promise for a peaceful future than and narrow emphasis on the idea of reconciliation.

Moral perspectives on covert research

The term ‘covert research’ refers to research on human subjects for which informed consent is not, and allegedly cannot, be solicited – not because of wilful negligence or the deliberate transgression of research ethics guidelines on the part of the researcher(s), but because the revelation of the nature of the research to the involved research participants would necessarily invalidate the research results. While covert research is deemed necessary in a number of sciences, such as ethnography, such research nevertheless elicits major ethical concern due to the fact that it seemingly violates the values of respect for autonomy and the protection of research subjects – values that have, since the first formulations of the Nuremberg Code, the Belmont Declaration and the series of Helsinki accords, become almost axiomatic in our understanding of the basic tenets of responsible and ethical research on human subjects. In this article, I contend that while subject autonomy is a pivotal value in morally legitimate research generally, there is more to morally legitimate research than informed consent. I conclude by formulating a few guidelines for the identification of circumstances under which covert research might and might not be morally in order.