Optimal interpolation method to predict the bathymetry of Saldanha Bay

Accurate interpolation when compiling bathymetric maps is essential in any water depth study. In the case of Saldanha Bay, continuous dredging operations are constantly altering the ocean floor, which has a detrimental effect on sedimentation and coastal hydrodynamics. If the integrity of the coastline is to be secured, accurate bathymetry predictions would be invaluable in determining the effect of dredging operations on coastal erosion. Inverse distance weighting (IDW) and ordinary kriging (OK) are two well-known and commonly used interpolation methods to produce surfaces through spatial autocorrelation for numerous applications, inter alia, to estimate bathymetry. This study aims to analyse and compare the efficiency of the IDW and OK interpolation methods to predict the bathymetry of Saldanha Bay. Three comparative interpolation tests, which vary according to the decrease in the quantity of sounding points, are conducted. SPSS statistical software was used to assess the performance of the interpolation methods. Firstly, 2D scatterplots were used to show the correlation between predicted and measured sounding values for each interpolation method. Secondly, analysis of variance was employed to investigate whether the difference between the IDW and OK interpolation methods was statistically significant, and to determine which method was best suited for determining the bathymetry of Saldanha Bay. Findings revealed a strong linear relationship between predicted and measured sounding values for both IDW and OK when 100% of the sounding points are used. Conversely, for medium and small quantities of sounding points, a weak correlation exists. Clear similarities exist in the way that IDW and OK estimate and generate the continuous surface of bathymetry. However, IDW consistently performed better than OK across all interpolation tests. The findings of this study will assist in selecting the most suitable interpolation method for future bathymetry surveys of Saldanha Bay

Understanding crime in the context of COVID-19: The case of Saldanha Bay Municipality

South Africa faces high levels of crime. The Saldanha Bay Municipality, the setting of this study, is laden with poverty, unemployment and gangsterism that deprive quality of life and contribute to social ills. While crime management and prevention strategies require information regarding crime trends, this information for the Saldanha Bay Municipality area is limited. Hence, the study aimed to illustrate the spatial distribution and trends of crime in the Saldanha Bay Municipality, focusing on the period January 2017 to June 2020, and to indicate the recent impact of COVID-19 on these crime trends. The results of the study are presented by means of graphs and tables, and hotspot mapping was done using the ArcGIS Getis-Ord Gi* statistics tool. These results indicate that crime has increased over the past three years and that criminal activities are linked to urban hubs where most people stay and work. In terms of the effect of the COVID-19 pandemic and the lockdown regulations on crime, it is interesting to note the variations in crime rates during the first three months of lockdown (from April 2020 to June 2020) when compared to the rest of the period under investigation. Amongst the five towns investigated, the town of Vredenburg which has the highest population total and was ranked highest in terms of crime rates prior to the lockdown, moved from first to third, behind Langebaan and St Helena Bay. Similarly, Saldanha Bay with the second highest population total moved down to fourth. Hopefield was still the town with the lowest mean crime rate

Food wastage management at the South African Military Academy officers’ mess

Globally, an estimated one-third of the total of food produced for human consumption is never consumed. This affects food security. South Africa has obligations to meet international commitments to reduce food wastage. The United Nations Sustainable Development Goal (SDG) 12.3 aims to reduce food loss through wastage by 30 per cent by 2030. To contribute to the achievement of this goal, South Africa has to formulate policies to reduce food loss to achieve national food security. The South African National Defence Force (SANDF), as an organ of the state, should align with national policies aimed at reducing food loss and waste. The current study was conducted at the South African Military Academy (SAMA), an institution of higher learning for SANDF members. The institution has a catering facility that serves approximately 350 resident students and other living-in members375 daily. To date, no research has been done on food wastage management either in the broader SANDF or at this institution. This lack of information and analysis on food wastage management in the military in South Africa prompted the current research. The study analysed food wastage management at the SAMA mess to identify the level of knowledge and skills of SAMA officers’ mess personnel regarding the status of food wastage and best management practices. Through this qualitative study, online semi-structured interviews, using Microsoft Teams, were utilised to collect data from SAMA mess personnel. The findings revealed that there are set measures in place at the SAMA mess for managing food wastage, such as booking meals in advance and being able to repurpose food. The participants also indicated that most SAMA chefs are trained in food wastage management and possess the necessary skills to reduce food wastage in the mess; yet, not optimally so. Recommendations from this research are that more and improved training of personnel, as well as awareness programmes among mess staff and SAMA students would further reduce food wastage. Implementing such food wastage management measures would benefit the SAMA and the SANDF, and would contribute to national food wastage management and the realisation of the United Nations SDG 12.3

Accuracy comparison of Pléiades satellite ortho-images using GPS device based GCPs against TerraSAR-X-based GCPs

Conducting single frame orthorectification on satellite images to create an ortho-image requires four basic components, namely an image, a geometric sensor model, elevation data (for example a digital elevation model (DEM)) and ground control points (GCPs). For this study, orthorectification entailed the use of a single scene Pléiades primary panchromatic image, applying the Pléiades rigorous geometric model, utilising a high-quality 2 m DEM and using GCPs that were acquired from two different collection methods. The application of these different GCPs to the execution of orthorectification encompassed the aim of this paper, which was to investigate and compare the positional accuracies of ortho-images under two scenarios. Firstly, GCPs were manually collected through fieldwork utilising a Trimble GeoExplorer 6000 series handheld GPS device and secondly, by utilising TerraSAR-X based GCPs that were acquired from Airbus Defence and Space. The objective of this study was to determine the geolocation accuracy of a high-resolution satellite ortho-image when different types of ground control are used. This required the execution of two orthorectification tests where only the type of GCPs differed. The results of these tests were interesting since it highlighted the difference in positional accuracy when utilising various sources of ground control to perform orthorectification on satellite imagery. The comparison results showed that utilising the manual GCPs produced a better positional accurate ortho-image as opposed to using the TerraSAR-X based GCPs. Nonetheless, the TerraSAR-X based GCPs still produced a sub 2 m accurate ortho-image, which is more than sufficient for the production of most geospatial products.Keywords: orthorectification, digital elevation model (DEM), ground control point (GCP), high-resolution satellite imagery, TerraSAR-X based GCPs, WorldDEM™, Airbus Defence and Spac

Determining the change in the bathymetry of Saldanha Bay due to the harbour construction in the seventies

ENGLISH ABSTRACT: Bathymetry is the science to study and measure the depths of the ocean floor. The differences in water depth, underwater slope and ocean floor structure were investigated using a geographic information system (GIS). This article investigates changes to the hydrodynamic sedimentation processes in Saldanha Bay as a result of the harbour constructions that took place in the early 1970s. The construction of the harbour included the massive dredging operations and resultant relocation of 30 million m3 of soil. Bathymetric data from Saldanha Bay before (1957) and after (1977) the construction of the harbour in the early seventies were analysed and compared in ArcGIS. It was found that the overall depth of the inner part of Saldanha Bay increased with about 1.4 m and that the bottom and slopes were smoothed. The physical structure that was constructed for the harbour had a serious impact on the hydrodynamic sedimentation processes. It was found that these interventions altered the depth profile of the Bay and the article finally draws conclusions on coastal and beach formation, based on the change in the hydrodynamic sedimentation processes of Saldanha Bay

Accuracy comparison of satellite images using alternative ground control points (GCPs) through performing orthorectification

No abstract available

Geometric accuracy improvement of VHR satellite imagery during orthorectification with the use of ground control points

Conducting single frame orthorectification on satellite images to create an ortho-image requires four basic components, namely an image, a geometric sensor model, elevation data (for example a digital elevation model (DEM)) and ground control points (GCPs). For this study, orthorectification was executed numerous times (in three stages) and each time components were altered to test the geometric accuracy of the resulting ortho-image. Most notably, the distribution and number of ground control points, the quality of the elevation source and the geometric sensor model or lack thereof were altered. Results were analysed through triangulating and comparing the geolocation accuracy of the ortho-images. The application of these different methods to perform orthorectification encompass the aim of this paper, which was to investigate and compare the positional accuracies of ortho-images under various orthorectification scenarios and provide improved geometric accuracies of VHR satellite imagery when diverse ground control and elevation data sources are available. By investigating the influence that the distribution and number of GCPs and the quality of DEMs have on the positional accuracy of an ortho-image, it became clear that a reasonable increase in the number of uniformly distributed GCPs combined with progressively accurate DEMs will ultimately improve the quality of the orthorectified product. The results also showed that when more GCPs were applied, the smaller the difference in accuracy was between the different DEMs utilised. It was interesting to note that when it is suitable to manually collect well-distributed GCPs using a GPS handheld device over the study area then a very accurate result can be expected. Nonetheless, it is also important to note that if it is not possible/practical to achieve the latter, satellite based GCP collection do provide a very good alternative. It was also determined that utilising GCPs which were extracted from vector road layers to only cover specific areas in the image scene produced less favourable results. Several contributions towards improved orthorectification procedures were made in this study. These include the development of an automatic GCP extraction script (A-GCP-ES), written in the Python scripting language with the purpose to ease the process of manually placing GCPs on an input image when repeatedly performing orthorectification.Thesis (PhD)--University of Pretoria, 2016.Geography, Geoinformatics and MeteorologyPhDUnrestricte

Prisoners of geography : ten maps that tell you everything you need to know about global politics

CITATION: Henrico, I. 2020. Prisoners of Geography : ten maps that tell you everything you need to know about global politics. Scientia Militaria, South African Journal of Military Studies, 48(1):133-137, doi:10.5787/48-1-1298.The original publication is available at http://scientiamilitaria.journals.ac.zaTim Marshall is an esteemed authority on foreign affairs, with more than thirty years’ experience in broadcasting, reporting, analysis and writing about past, present and future geopolitical affairs – most of the time reporting from the front line on major world events and conflict zones that had significant geopolitical effects on global politics, such as the Balkan wars of the 1990s, the Kosovo crisis of 1999, the first Gulf War (1991), the US war in Afghanistan (2001). He also covered three US presidential elections (The What and The Why, 2016). Prisoners of geography: Ten maps that tell you everything you need to know about global politics is arguably the most successful of his books, and makes for an intriguing read by an author with such an impressive résumé.https://scientiamilitaria.journals.ac.za/pub/article/view/1298Publisher's versio

Understanding crime using GIS and the context of COVID-19: The case of Saldanha Bay Municipality

South Africa faces high levels of crime. The Saldanha Bay Municipality, the setting of this study, is laden with poverty, unemployment and gangsterism that deprive quality of life and contribute to social ills. While crime management and prevention strategies require information regarding crime trends, this information for the Saldanha Bay Municipality area is limited. Hence, the study aimed to illustrate the spatial distribution and trends of crime in the Saldanha Bay Municipality, focusing on the period January 2017 to June 2020, and to indicate the recent impact of COVID-19 on these crime trends. The results of the study are presented by means of graphs and tables, and hotspot mapping was done using the ArcGIS Getis-Ord Gi* statistics tool. These results indicate that crime has increased over the past three years and that criminal activities are linked to urban hubs where most people stay and work. In terms of the effect of the COVID-19 pandemic and the lockdown regulations on crime, it is interesting to note the variations in crime rates during the first three months of lockdown (from April 2020 to June 2020) when compared to the rest of the period under investigation. Amongst the five towns investigated, the town of Vredenburg which has the highest population total and was ranked highest in terms of crime rates prior to the lockdown, moved from first to third, behind Langebaan and St Helena Bay. Similarly, Saldanha Bay with the second highest population total moved down to fourth. Hopefield was still the town with the lowest mean crime rate.