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.
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.
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
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.
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 3 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.
Geographic Information Systems (GIS) consists of various tools to perform spatial analyses in a wide variety of disciplines, including radiometric analysis to characterize the distribution of natural radionuclide concentrations. Recently, open-source GIS has become popular among geospatial users because it can be freely used, and powerful tools are constantly developed to enhance software capabilities. Gamma-ray spectroscopy was used to measure the concentrations of these natural radionuclides by dragging a Delta Underwater Gamma System (DUGS) among the sediment in the Berg River estuary located in Velddrif, South Africa. In this study, QGIS was used to visually illustrate and interpret the distribution of natural radionuclides, that is, potassium (K 40 ), thorium (Th 232 ), and uranium (U 238 ). These concentrations can be used to investigate various geographical and geological phenomena, which include sediment processes. The data were then interpreted to derive sediment characteristics. Various features of tidal estuaries were demonstrated by the results.
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