South African Journal of Geomatics最新文献

{"title":"Analysis of thermally-induced displacements of the HartRAO Lunar Laser Ranger optical tube: impact on pointing","authors":"Philemon Tsele, Ludwig Combrinck, Roelf Botha, Bongani Ngcobo","doi":"10.4314/sajg.v12i.2.8","DOIUrl":"https://doi.org/10.4314/sajg.v12i.2.8","url":null,"abstract":"The Hartebeesthoek Radio Astronomy Observatory (HartRAO) of South Africa is developing a Lunar Laser Ranging (LLR) system to achieve sub-centimetre range precision to the Moon. Key to this high precision expectation, which includes improving the overall operational performance of its telescope, is the thermal analysis of the telescope structure. In this study, thermal sensors were mounted on the thermally- important areas of the tube structure to measure the tube displacements emanating from the varying ambient air temperatures. A laser distance-measurement system was used for this purpose. Results showed that while the optical tube undergoes structural changes with changes in temperature, the tube position closer to the place where the spider assembly is mounted is unevenly displaced in three directions. In particular, for the time period considered in this study, it was found that the relative displacements on average at prisms 1, 2 and 3 in the vertical direction were 2.5540 ± 0.0007 m, 1.3750 ± 0.0008 m and 1.9780 ± 0.0007 m, respectively. The corresponding standard deviation (SD) values of ±0.0007 m, ±0.0008 m and ±0.0007 m denotes the average deviations that occurred in the vertical direction at the centre of prisms 1, 2 and 3, respectively. The generally higher SD of relative displacements in the vertical direction rather than in the easting and northing directions, suggest that the tube experienced greater variations in the vertical direction. Furthermore, the lower arc of the tube front, was found to have increased variability, and therefore it was hypothesised to introduce more elevation pointing offsets than azimuth for the LLR. This information constitutes an important input for guiding the efforts to determine the extent of the correction needed to be fed into the LLR telescope pointing model to counteract expected thermally induced pointing offsets.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":"57 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135461267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identifying the optimal phenological period for discriminating subtropical fruit tree crops using multi-temporal Sentinel-2 data and Google Earth Engine","authors":"Yingisani Chabalala, Elhadi Adam, Khalid Adem Ali","doi":"10.4314/sajg.v12i.2.10","DOIUrl":"https://doi.org/10.4314/sajg.v12i.2.10","url":null,"abstract":"The accurate and appropriate monitoring of the spatial distribution of fruit tree crops is crucial for crop management and yield forecasting. Owing to both inter- and intra-farm fragmentation and overlapping phenological cycles, the classification of fruit tree crops in subtropical agriculture using single-date images is challenging. Therefore, this research aimed to identify the optimal temporal window in which the crucial phenological stages can be used to classify fruit tree crops in Levubu, Limpopo province, using a random forest (RF) classifier. Phenological metrics were extracted from 12-month Multispectral Instrument (MSI) images from Sentinel-2 (S2). The RF classification algorithm attained an overall accuracy of 84.89% and a kappa coefficient of 83%. The user accuracy ranged from 62 to 100%, while the producer accuracy ranged from 60 to 100%. An analysis of variance was used to assess whether the overall accuracies among the S2 monthly composites were statistically significant. The results showed distinct spectral differences between fruit trees. In April, there were differences observed during the harvesting and senescence of the mango and macadamia nut crops. In May, there were differences observed during the senescence of the macadamia nut, mango, and guava crops. In June and July, there were distinct spectral differences during the peak flowering stage of the avocado, macadamia nut, and mango crops, as well as in the fruiting stage of the banana crops. Followed by the red-edge bands, the shortwave infrared bands were significant in differentiating between the respective fruit tree crops. The results of this research provide evidence-based information that can assist farm managers and horticulturists in making informed decisions. This is critical in achieving effective agricultural management and in ensuring the sustainability of local horticultural systems.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135665852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessing the importance of hypsometry for catchment soil erosion: A case study of the Yanze watershed, Rwanda","authors":"Faustin Gashakamba, Umaru Garba Wali, Vaillant Rutazuyaza Byizigiro","doi":"10.4314/sajg.v12i.2.9","DOIUrl":"https://doi.org/10.4314/sajg.v12i.2.9","url":null,"abstract":"Implementing a watershed erosion control programme requires resource-intensive and time-consuming preliminary studies to prioritize such interventions and to focus on those sub-catchments where they are most likely to yield the most effective results.
 In this study, we explore and document the effectiveness of using hypsometric analysis as a method to prioritize erosion control measures and apply it to the Yanze watershed located in central Rwanda.
 Based on a 30m-resolution DEM of the watershed and using ArcGIS and R software, we made estimates of hypsometric integral values and calculated soil loss estimates through RUSLE modelling and by using data from different sources, namely the Rwanda Meteorological Agency (rainfall data), ISRIC (soil data), and Sentinel-2 images (land cover maps).
 The hypsometric integral values of the Yanze sub-catchments were high, ranging from 0.5 to 0.936. This, combined with the overall convex upward hypsometric curves, indicates that the Yanze watershed is still at a youthful stage in its erosional cycle.
 The results of the RUSLE model showed that the average potential soil loss in the Yanze watershed is 55.63 tonnes.ha-1.year-1, which is comparable to the national average estimated at 62 tonnes.ha-1.year-1.
 The correlation analysis that we conducted between the hypsometric integral values of the Yanze sub-catchments and their respective mean soil loss values revealed no correlation between the two variables. From the results of this study, we conclude that in watersheds where lithology affects soil erosion significantly, morphology can indeed indicate the potential for erosion. However, we further concluded that future studies to characterize erosion potential using morphometry should employ additional morphometric parameters in the regression model.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135666080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Investigation into the Stability of some selected Geodetic Controls in Lagos State of Nigeria using the Strain Analysis Technique","authors":"O.G. Omogunloye, S. Bawa, O. E. Abiodun, O. A. Olunlade, T. J. Salami, A. O. Alabi","doi":"10.4314/sajg.v12i.2.4","DOIUrl":"https://doi.org/10.4314/sajg.v12i.2.4","url":null,"abstract":"Natural disasters pose global challenges and can result in social, economic, and environmental damage, substantial loss of life, and even pose a threat to geopolitical stability. The study of such disasters through deformation modeling and analyses has found application in the disciplines of Geodesy and Geodynamics. The strain method has in fact been used to model deformation. The strain deformation parameters, namely, dilatancy, total shear strain and differential rotation, of this finite elemental model were calculated by using the baseline ratios of the coordinates of a classical traverse observed using the Global Positioning System (space technique), in the Minna datum platform. Computation was undertaken in a MATLAB programme and a MONTE CARLO environment, after the ill-conditioned triangles in the network were excluded. Statistical analysis was used to determine the significance levels of the respective deformation parameters at the 95%, 97.5% and 99.5% confidence intervals. After the statistical testing of the deformation parameters, it was observed that some of the controls were unstable in terms of their computed dilatancy and their total shear strain values. For the differential rotation of the network, the significance levels at the 95%, 97.5% and 99.5% confidence intervals were found to be 1.8743908, 0.9651796 and 0.4338522, respectively, while, on the other hand, the controls or centroids that did not respond to the network rotation had a mean value of approximately -0.99999.The minimal and maximal principal strain levels occurring at Centroids 11 and 36 with their triangulated station identities were found to be (36-12, 30-84, 43-34A) and (34-30A, 34-32A, 34-36A), respectively. The method adopted for this research proved to be very effective for a deformation study and analysis.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136000223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigating the efficiency and capabilities of UAVs and Convolutional Neural Networks in the field of remote sensing as a land classification tool","authors":"Cameron Wesson, Wilma Britz, Robbert Duker","doi":"10.4314/sajg.v12i.2.5","DOIUrl":"https://doi.org/10.4314/sajg.v12i.2.5","url":null,"abstract":"The study aimed to determine the efficacy and capabilities of using high-resolution aerial imagery and a convolutional neural network (CNN) to identify plant species and monitor land cover and land change in the context of remote sensing. The full capabilities of a CNN were examined, including testing whether the platform could be used for land cover and the evaluation of land change over time. An unmanned aerial vehicle (UAV) was used to collect the aerial data of the study area. The CNN was encoded and operated in RStudio, while digitised data from the input imagery were used by the programme as training and validation data. The object in this respect was to learn about the relevant features of the landscape, and thereafter to classify the Opuntia invasive plant species. Accuracy assessments were carried out on the results to test the efficacy of the aerial imagery in terms of its accuracy and reliability. The classification achieved an overall accuracy of 93%, while the kappa coefficient score was 0.86. CNN was also able to predict the land coverage area of Opuntia to be within four percent (4%) of the ground truthing data. A change in land cover over time was detected by the programme after the manual clearing of the plant had been undertaken. This research has determined that the use of a CNN in remote sensing is a very powerful tool for supervised image classifications. It can be used for monitoring land cover in that it is able to accurately estimate the spatial distribution of plant species and to monitor the growth or decline in the species over time. As such, it is an efficient methodology and its use in remote sensing could be extended.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135998923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Classification of 3D UAS-SfM Point Clouds in the Urban Environment","authors":"Simiso Ntuli, Angus Forbes","doi":"10.4314/sajg.v12i.2.6","DOIUrl":"https://doi.org/10.4314/sajg.v12i.2.6","url":null,"abstract":"The classification of three-dimensional (3D) point clouds derived through the use of cost-effective and time-efficient photogrammetric technologies can provide helpful information for applications, particularly in the mapping context. This paper presents a practical study of 3D Unmanned Aerial System (UAS) – Structure-from-Motion (SfM) point cloud classification using mainly open-source software. Following a supervised classification approach that makes use of only the dimensionality of points, the entire scene was classified into three land-cover categories: ground, high vegetation, and buildings. By applying the above-mentioned approach, the level of competence in classifying a 3D point cloud of a heterogeneous scene situated in the University of KwaZulu-Natal, South Africa, was evaluated. The resulting overall classification accuracy of 81.3%, with a Kappa coefficient of 0.70, was determined by means of a confusion matrix. The results achieved indicate the potential use of open-source software and 3D UAS-SfM point cloud classification in mapping and monitoring complex environments and in other applications that might arise.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135998922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Geographically Weighted Regression Analysis of Barriers to Youth’s Participation in Local Development Planning in Gauteng Province, South Africa","authors":"Koech Cheruiyot","doi":"10.4314/sajg.v12i.2.1","DOIUrl":"https://doi.org/10.4314/sajg.v12i.2.1","url":null,"abstract":"With South Africa having a history of youth activism and a predominantly youthful population, this paper investigates why the youth (18-34 years) do not participate in local development planning in Gauteng Province. The main source of data used in this study was the 2015/2016 QoL data of the Gauteng City-Region Observatory (GCRO). Results across Gauteng show that the majority of the youth do not participate in ward committee (WC), community development forum (CDF), and integrated development planning (IDP) meetings. The geographically weighted regression (GWR) approach proved important in allowing us to investigate the spatial variation in non-attendance at WC meetings and the heterogeneity role of the predictor variables over the study area. The GWR results show that the percentage of employed youth, average household income, the percentage of youth who have never interacted with government, the percentage of youth dissatisfied with the local councillor, and the average educational level of the youth emerged as barriers to participation in WC meetings. While results for non-participation in CDF meetings had no significant localised GWR results, compared to those for WC meetings, common barriers (as in the ordinary least squares (OLS) model) to participation in CDF meetings were, for instance, the youth’s educational level and the lack of interaction with local government. Even according to the OLS model, the results of IDP meetings were not robust, and could not therefore be interpreted. Overall, however, these results are useful in spurring spatially-targeted – either region-wide or localised – policies.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":"178 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136000224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Homogenizing coordinates through the use of the active CORS in Ghana","authors":"Osman Mohammed Abukari, Akwasi Afrifa Acheampong, Samuel Osah, John Ayer","doi":"10.4314/sajg.v12i.2.2","DOIUrl":"https://doi.org/10.4314/sajg.v12i.2.2","url":null,"abstract":"In this study, the course towards determining the homogeneous three-dimensional (3D) coordinates of the newly established active Continuously Operating Reference Station (CORS), based on ITRF2014 in Ghana, is revealed. The aim is to address coordinate inconsistencies and inhomogeneity in the published positions of the new active CORS in Ghana. In order to attain homogeneity, the coordinates of two primary control points, GCS 305 and GCS 306, were obtained using AUSPOS online services via email. These were subsequently used as reference stations to compute the position of the LISAG_KUMASI CORS. Adjustments to the position coordinates were performed using Topcon Tools v8.2.3 software at a 1mm standard deviation. The adjusted coordinates of LISAG_KUMASI were used as the reference points to compute the positions of the LiSAGNet CORS in differential mode by using 24 hour data for 11 consecutive days. The GPS data covered DoY 284 to DoY 295 in 2021. The final positions of the CORS, computed by this approach, indicate some differences from the officially published coordinates of the same CORS, confirming the suspicion of inhomogeneity in the source coordinates used in determining the coordinates of the local CORS. Furthermore, a test network, consisting of five COR stations, was designed and used to address the coordinate inconsistencies in the officially published coordinates. Using the officially published coordinates as reference inputs, the ROVER I station was fixed by three different CORSs, thus resulting in average coordinate variabilities of 2.78m and 0.80m in the northing (N) and easting (E) directions, respectively. Through substitution, the coordinates computed in this study as reference inputs, namely, the ROVER I station, were fixed by the same three CORSs, thus resulting in a coordinate variability of 0.002m and 0.006m in the northing (N) and easting (E) directions, respectively. The analysis revealed inconsistencies and inhomogeneity in terms of the officially published coordinates. It is, therefore, recommended that the officially published coordinates of the CORS be replaced by the adjusted homogeneous and consistent values determined through the approach adopted in this study.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136000225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Application of GIS to monitor infrastructural development in Mombasa County, Kenya","authors":"Margaret N. Munywoki, Kaveer Singh","doi":"10.4314/sajg.v12i.2.3","DOIUrl":"https://doi.org/10.4314/sajg.v12i.2.3","url":null,"abstract":"The Government of Kenya, under its Vision 2030 Agenda, highlighted the need for decent and high-quality livelihoods for its citizens, by ensuring that sustainable provision be made for the necessary infrastructure required to meet their socio-economic needs. Thus, the government invested in an Electronic Development Application Management System (e-DAMS). It allows the Built Environment professionals to register and apply for planning certificates, construction permits, building inspection permits, and occupation permits. However, this system can only regulate and monitor the existing infrastructure projects in the database and has to exclude unauthorised developments. This GIS approach, which was built upon the recording and tracking of several types of electricity applications made by customers, could also be used to monitor new and existing infrastructure developments. Data were sourced from multiple government agencies in Mombasa County. A comparative analysis approach was subsequently employed to investigate the relationship between the trends in electricity supply applications, the respective types of urban land-use development, and the permits issued in approving the respective types of construction in Mombasa County. A direct relationship was found between the permits used to approve the respective types of construction and the Urban Development Master Plan. Also, a direct relationship was found between the applications for the respective types of electricity that were being made and the issuing of construction approval permits. The conclusion was reached that the applications for the prevailing types of electricity supply could be used as a proxy for identifying and assessing infrastructural development in Mombasa County. This GIS approach could provide the authorities with insights into unauthorised construction initiatives.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135998924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geospatial Analysis of Informal Settlement Development in Cape Town","authors":"T Fisher, K Singh","doi":"10.4314/sajg.v12i.2.7","DOIUrl":"https://doi.org/10.4314/sajg.v12i.2.7","url":null,"abstract":"Informal settlements are a major influence in the urban growth of developing countries such as South Africa. There are also associated with negative socio-economic factors such as unemployment and are lacking in terms of secure land tenure arrangements. This research focuses on developing a geospatial understanding of the internal dynamics of informal settlement development within the City of Cape Town. To investigate how informal settlements are established and developed in a local context, the informal settlements of Imizamo Yethu, Langa, and Siqalo were monitored for the period 2011-2019 using image classification to determine the development, complexity, and compactness of the dwellings. The overall accuracy of the classified maps thus developed ranged between 88 and 96%. Change detection analysis was subsequently used to identify the geospatial trends for each informal settlement across all three. The combination of linear regression and ordinary least squares analysis determined that the major spatial trend driving growth was densification, which was correlated with the availability of open space, unemployment, poverty, and GDP. Furthermore, densification was identified along the major formal external transport routes and informal internal transport networks. It was found that individual settlements present unique internal geospatial development dynamics in the macroeconomic context of Cape Town, but that these tend to differ in the microeconomic context of the city. Among the explanatory variables for this situation were sloped lands, employment opportunities, and neighbouring areas where the incomes of the residents were higher. Across all the informal settlements, open space proved to be the most significant factor, while GDP played the most influential role in explaining shack compactness over time. This study could be used to contribute to policy and decision-making in the formalisation process in these informal settlements.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136000226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}