This study examined the spatiotemporal pattern of urban growth and magnitude of changes in selected Local Government Areas (LGAs) in the suburban area of Ibadan using remote sensing cum spatial metrics. Data for the study were obtained from administrative maps of the study area, population data and satellite imageries. All of these were complemented with ground validations using Global Positioning System (GPS) receiver. Periods of change analysis were divided into two epochs; 1986 to 2002 and 2002 to 2017. The imageries were classified into four landuse/cover classes based on Anderson’s modified version of supervised classification scheme. Accuracy assessment of the imageries was carried out using 100 randomly sampled ground truth points. Ten spatial metrics were selected for analysis using Fragstats program. Results show a significant loss in vegetation due to conversion (Land Consumption Rate, LCR = 0.025, 0.019 and 0.027; Land Absorption Coefficient, LAC = 0.012 and 0.048). Moreover, there was a persistent increase in Number of Patches (NP) indicating a scattered and fragmented but continuous development. However, dwindling values of Patch Density (PD = 90.94, 27.07 and 30.30) indicate expansion through conversion of other landuses at varying rates. Results also indicate an incidence of fragmented low density development in the fringe areas (Area Weighted Mean Patch Fractal Dimension, AWMPFD = 1.37 and 1.39). The study highlights the chaotic land development and unrestrained urban expansion in the study area.
{"title":"Landscape metrics analysis of land use patterns and changes in suburban local government areas of Ibadan, Nigeria","authors":"A. Olayiwola, O. Fakayode","doi":"10.4314/sajg.v8i2.7","DOIUrl":"https://doi.org/10.4314/sajg.v8i2.7","url":null,"abstract":"This study examined the spatiotemporal pattern of urban growth and magnitude of changes in selected Local Government Areas (LGAs) in the suburban area of Ibadan using remote sensing cum spatial metrics. Data for the study were obtained from administrative maps of the study area, population data and satellite imageries. All of these were complemented with ground validations using Global Positioning System (GPS) receiver. Periods of change analysis were divided into two epochs; 1986 to 2002 and 2002 to 2017. The imageries were classified into four landuse/cover classes based on Anderson’s modified version of supervised classification scheme. Accuracy assessment of the imageries was carried out using 100 randomly sampled ground truth points. Ten spatial metrics were selected for analysis using Fragstats program. Results show a significant loss in vegetation due to conversion (Land Consumption Rate, LCR = 0.025, 0.019 and 0.027; Land Absorption Coefficient, LAC = 0.012 and 0.048). Moreover, there was a persistent increase in Number of Patches (NP) indicating a scattered and fragmented but continuous development. However, dwindling values of Patch Density (PD = 90.94, 27.07 and 30.30) indicate expansion through conversion of other landuses at varying rates. Results also indicate an incidence of fragmented low density development in the fringe areas (Area Weighted Mean Patch Fractal Dimension, AWMPFD = 1.37 and 1.39). The study highlights the chaotic land development and unrestrained urban expansion in the study area.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2019-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49420118","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}
Several ecosystems have been significantly altered by anthropogenic nitrogen inputs. The timely estimation of nitrogen concentration is essential for ensuring environmental sustainability. Academic publications between 1966 and 2016 were reviewed to assess the potential of remotely sensed information to estimate nitrogen concentrations for various applications. A discriminatory keyword search and a set of inclusion criteria was used to develop a representative sample (n = 100). Results revealed that the global distribution of academic publications is skewed towards the Northern Hemisphere with the largest research gap occurring within Africa. Moreover, prior to 2006, research into the remote estimation of nitrogen had a minor presence in literature, with the agricultural sector being the most extensively researched (56%). Freely available, high spatial and temporal resolution imagery has afforded research into the remote estimation of nitrogen in the African continent, particularly in the subject area of policy and management, the capacity to grow.
{"title":"Estimation of foliar nitrogen using remotely sensed data: A quantitative review","authors":"Rowan Naicker, O. Mutanga, K. Peerbhay","doi":"10.4314/sajg.v8i2.6","DOIUrl":"https://doi.org/10.4314/sajg.v8i2.6","url":null,"abstract":"Several ecosystems have been significantly altered by anthropogenic nitrogen inputs. The timely estimation of nitrogen concentration is essential for ensuring environmental sustainability. Academic publications between 1966 and 2016 were reviewed to assess the potential of remotely sensed information to estimate nitrogen concentrations for various applications. A discriminatory keyword search and a set of inclusion criteria was used to develop a representative sample (n = 100). Results revealed that the global distribution of academic publications is skewed towards the Northern Hemisphere with the largest research gap occurring within Africa. Moreover, prior to 2006, research into the remote estimation of nitrogen had a minor presence in literature, with the agricultural sector being the most extensively researched (56%). Freely available, high spatial and temporal resolution imagery has afforded research into the remote estimation of nitrogen in the African continent, particularly in the subject area of policy and management, the capacity to grow.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2019-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42213554","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}
Formal land registration systems have failed to accommodate the wide range of land tenure claims found in developing countries, including land rights under customary and informal tenure systems, thereby leaving the rural people with insecure tenure. To reduce poverty, empower the poor, and ensure economic growth, security of tenure is beneficial. This paper investigates how the Social Tenure Domain Model (STDM) can be applied to record customary and informal land rights at Itaji-Ekiti, Nigeria. Primary data was collected by administering questionnaires on a house-to-house basis and conducting interviews with land rights holders. Spatial data was recorded using a handheld Global Positioning System (GPS) Garmin Oregon 300 and a mobile application (Topographic Mapper). Secondary data was collected from reports, journal articles, published books and the Google Earth image repository. The data collected through the administered questionnaires was used to analyse perceptions of tenure by the holders of land rights. This study provides additional knowledge for researchers in the field of Cadastral Surveying, as it tested the applicability of the STDM. The model will also help the government of Nigeria with the necessary data for the upgrading of informal settlements, which will provide integrity in land administration.
{"title":"Using a domain model of social tenure to record land rights: A Case Study of Itaji-Ekiti, Ekiti State, Nigeria","authors":"K. H. Babalola, Simon Hull","doi":"10.4314/sajg.v8i2.8","DOIUrl":"https://doi.org/10.4314/sajg.v8i2.8","url":null,"abstract":"Formal land registration systems have failed to accommodate the wide range of land tenure claims found in developing countries, including land rights under customary and informal tenure systems, thereby leaving the rural people with insecure tenure. To reduce poverty, empower the poor, and ensure economic growth, security of tenure is beneficial. This paper investigates how the Social Tenure Domain Model (STDM) can be applied to record customary and informal land rights at Itaji-Ekiti, Nigeria. Primary data was collected by administering questionnaires on a house-to-house basis and conducting interviews with land rights holders. Spatial data was recorded using a handheld Global Positioning System (GPS) Garmin Oregon 300 and a mobile application (Topographic Mapper). Secondary data was collected from reports, journal articles, published books and the Google Earth image repository. The data collected through the administered questionnaires was used to analyse perceptions of tenure by the holders of land rights. This study provides additional knowledge for researchers in the field of Cadastral Surveying, as it tested the applicability of the STDM. The model will also help the government of Nigeria with the necessary data for the upgrading of informal settlements, which will provide integrity in land administration.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2019-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41686195","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}
Lake Chad is located at the south of the Sahara Desert in an arid region. The lake’s water resources are under severe pressure due to the basic needs of the growing population around the lake, global warming, and increasing irrigation demands. Numerous land cover change studies have measured the rate of depletion of the lake’s surface water. However, the contribution of the increasing high temperatures in the region which is also a compounding factor has received little attention. In this study, an assessment of the changes in surface water extent of Lake Chad from 1973-2017 was carried out through a land cover analysis. The potential influence of the rising land surface temperatures on the water losses was also studied. The extraction of the land cover was done using maximum likelihood classification. The results show that between 1973 and 1987, the lake lost 12,796.81km2 of its surface water area. This period coincided with a season of drought and dry seasons reported to have occurred in the lake’s area during the 1970s. Between 1987 and 2003, average temperature rise and change in surface water area was +1.54˚C and +962.71km2 respectively. Between 2003 and 2017, average temperature rise and change in surface water area was +3.69˚C and -25.17km2 respectively. These results provide further evidence of the alarming rate of water loss in the lake’s environment, and suggest a link between rising land surface temperatures and diminution of the lake’s water. The findings inform efforts directed at addressing the ecological problem facing the lake.
{"title":"Spatio-temporal assessment of changing land surface temperature and depleting water in the Lake Chad area","authors":"P. Nwilo, A. A. Umar, M. Adepoju, C. Okolie","doi":"10.4314/sajg.v8i2.3","DOIUrl":"https://doi.org/10.4314/sajg.v8i2.3","url":null,"abstract":"Lake Chad is located at the south of the Sahara Desert in an arid region. The lake’s water resources are under severe pressure due to the basic needs of the growing population around the lake, global warming, and increasing irrigation demands. Numerous land cover change studies have measured the rate of depletion of the lake’s surface water. However, the contribution of the increasing high temperatures in the region which is also a compounding factor has received little attention. In this study, an assessment of the changes in surface water extent of Lake Chad from 1973-2017 was carried out through a land cover analysis. The potential influence of the rising land surface temperatures on the water losses was also studied. The extraction of the land cover was done using maximum likelihood classification. The results show that between 1973 and 1987, the lake lost 12,796.81km2 of its surface water area. This period coincided with a season of drought and dry seasons reported to have occurred in the lake’s area during the 1970s. Between 1987 and 2003, average temperature rise and change in surface water area was +1.54˚C and +962.71km2 respectively. Between 2003 and 2017, average temperature rise and change in surface water area was +3.69˚C and -25.17km2 respectively. These results provide further evidence of the alarming rate of water loss in the lake’s environment, and suggest a link between rising land surface temperatures and diminution of the lake’s water. The findings inform efforts directed at addressing the ecological problem facing the lake.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2019-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48432604","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}
O. I. Apeh, O. C. Nwaka, R. Ndukwu, Ikechukwu Maduako, Olatomiwa O. Arilewola
The interplay between Geographical Information System (GIS) and Computer Science has continued to yield improved methods of carrying out many surveying-related activities. In the past, survey control points were stored in file systems and at the best in Database Management applications thereby leading to the limited usage of the survey control points since they are difficult to locate in the field. This study however, suggests another approach for the storage of these survey control points which makes them to be easily accessible and gives room for faster update and geo-visualization of the survey control points. This was achieved by means of web programming applications such as Node-JS, Leaflet Javascript Mapping API, MONGODB, HTML and CSS, integrating GIS into web technologies. The end product is an interactive web application that can be accessed using any smart device with the control points rendered on the user interface. The Survey Control Finder application (E-Beacon) is a WebGIS platform for the geovisualisation of survey control stations in the University of Nigeria, Enugu campus (UNEC), Nigeria. This study gives insight into what the latest trend in technology has in store for surveying and the need to arouse the interest of learners in web application programming in order to develop more surveying-related applications.
地理信息系统（GIS）和计算机科学之间的相互作用继续改进了开展许多测量相关活动的方法。过去，测量控制点存储在文件系统中，最好存储在数据库管理应用程序中，因此导致测量控制点的使用有限，因为它们很难在现场定位。然而，这项研究提出了另一种存储这些测量控制点的方法，使其易于访问，并为更快地更新和地理可视化测量控制点提供了空间。这是通过网络编程应用程序实现的，如Node-JS、传单Javascript映射API、MONGODB、HTML和CSS，将GIS集成到网络技术中。最终产品是一个交互式网络应用程序，可以使用任何智能设备访问，并在用户界面上呈现控制点。Survey Control Finder应用程序（E-Beacon）是一个WebGIS平台，用于尼日利亚大学埃努古校区（UNEC）的测量控制站的地理可视化。本研究深入了解了测量技术的最新趋势，以及激发学习者对网络应用程序编程的兴趣以开发更多与测量相关的应用程序的必要性。
{"title":"E-beacon: a web-based survey control finder application","authors":"O. I. Apeh, O. C. Nwaka, R. Ndukwu, Ikechukwu Maduako, Olatomiwa O. Arilewola","doi":"10.4314/sajg.v8i2.5","DOIUrl":"https://doi.org/10.4314/sajg.v8i2.5","url":null,"abstract":"The interplay between Geographical Information System (GIS) and Computer Science has continued to yield improved methods of carrying out many surveying-related activities. In the past, survey control points were stored in file systems and at the best in Database Management applications thereby leading to the limited usage of the survey control points since they are difficult to locate in the field. This study however, suggests another approach for the storage of these survey control points which makes them to be easily accessible and gives room for faster update and geo-visualization of the survey control points. This was achieved by means of web programming applications such as Node-JS, Leaflet Javascript Mapping API, MONGODB, HTML and CSS, integrating GIS into web technologies. The end product is an interactive web application that can be accessed using any smart device with the control points rendered on the user interface. The Survey Control Finder application (E-Beacon) is a WebGIS platform for the geovisualisation of survey control stations in the University of Nigeria, Enugu campus (UNEC), Nigeria. This study gives insight into what the latest trend in technology has in store for surveying and the need to arouse the interest of learners in web application programming in order to develop more surveying-related applications.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2019-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44131890","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}
Toko Mouhamadou Inoussa, Oladejo Sunday Olukayode, Obayelu Igbekele Stephen
Most natural forests throughout the world have been destroyed and converted to human land uses to meet the ever growing demands for resources while the remaining forest landscapes consequently have a mosaic of human-modified land areas such as urban, agricultural, and plantation lands. Forest and forest products provide myriad of economic, financial and health importance. The threat to the rainforest compelled the establishment of forest reserves with the introduction of exotic tree species. The Oluwa forest is located between latitudes 6º37’ and 7 º20’ north and longitudes 4 º27’ and 5º05’ east in Ondo state, Nigeria. Species richness and abundance data are crucial for conservation priority setting, and long-term vegetation monitoring. Few studies have been carried out on the composition of Terminalia spp, diversity and richness in the institutional-based landuse. The aim of this work is to analyze the influence of topography on Terminalia species diversity for conservation purpose. Complete enumeration of the Natural forest was carried out to determine the varieties of Terminalia species in the study site. In all, two variety, Terminalia, superba and Terminalia ivorensis were identified. GPS coordinate their locations was overlaid on Elevation, Slope, Aspect and Hillshad. The area with low elevation, and low slope, high hillshade, and the west aspect showed maximum species abundance. The Shannon diversity index of Terminalia species was calculated and the result implies that the diversity/abundance is low in the study site. It was observed that the spatial distribution and relative abundance of these species was influenced by topographic factors. Despite the limited range of altitudinal variation (399 m), species richness increases with elevation. This work has provided evidence of variability in Terminalia species composition, richness and diversity across the topographic gradient. The information could be crucial for monitoring and providing conservative measure for management of species sustainability. A future study would be required to isolate proximate factors of tree species distribution.
{"title":"Topographic influence on Terminalia species diversity in Oluwa forest reserve, Ondo State (Nigeria)","authors":"Toko Mouhamadou Inoussa, Oladejo Sunday Olukayode, Obayelu Igbekele Stephen","doi":"10.4314/sajg.v8i2.9","DOIUrl":"https://doi.org/10.4314/sajg.v8i2.9","url":null,"abstract":"Most natural forests throughout the world have been destroyed and converted to human land uses to meet the ever growing demands for resources while the remaining forest landscapes consequently have a mosaic of human-modified land areas such as urban, agricultural, and plantation lands. Forest and forest products provide myriad of economic, financial and health importance. The threat to the rainforest compelled the establishment of forest reserves with the introduction of exotic tree species. The Oluwa forest is located between latitudes 6º37’ and 7 º20’ north and longitudes 4 º27’ and 5º05’ east in Ondo state, Nigeria. Species richness and abundance data are crucial for conservation priority setting, and long-term vegetation monitoring. Few studies have been carried out on the composition of Terminalia spp, diversity and richness in the institutional-based landuse. The aim of this work is to analyze the influence of topography on Terminalia species diversity for conservation purpose. Complete enumeration of the Natural forest was carried out to determine the varieties of Terminalia species in the study site. In all, two variety, Terminalia, superba and Terminalia ivorensis were identified. GPS coordinate their locations was overlaid on Elevation, Slope, Aspect and Hillshad. The area with low elevation, and low slope, high hillshade, and the west aspect showed maximum species abundance. The Shannon diversity index of Terminalia species was calculated and the result implies that the diversity/abundance is low in the study site. It was observed that the spatial distribution and relative abundance of these species was influenced by topographic factors. Despite the limited range of altitudinal variation (399 m), species richness increases with elevation. This work has provided evidence of variability in Terminalia species composition, richness and diversity across the topographic gradient. The information could be crucial for monitoring and providing conservative measure for management of species sustainability. A future study would be required to isolate proximate factors of tree species distribution.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2019-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42885263","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}
This study highlights the usage of deep learning artificial neural networks in the assessment of groundwater vulnerability of a coalfield. The network uses the DRIST model with parameters (depth to water level, recharge, impact of the vadose zone, soils and topographic slope) as training inputs and borehole sulphate concentration as training output. This technique was applied to Witbank coalfield, where acid mine drainage emanating from coal mining operations is a huge concern for surrounding environment and groundwater resources. The generated groundwater vulnerability model was validated with another sulphate dataset not used during model training. The deep neural network model with dropout and decaying learning rate regularisers correlated very well with sulphate data from another source as compared to the index and overlay DRIST model. The approach, differentiated areas in terms of vulnerability to acid mine drainage, which can aid policy, and decision makers to make scientifically informed decisions on land use planning. The approach developed in this research can be applied to other coalfields in order to evaluate its robustness to different hydrogeological and geological conditions.
{"title":"Groundwater vulnerability mapping of Witbank coalfield in South Africa using deep learning artificial neural networks","authors":"E. Sakala, F. Fourie, M. Gomo, H. Coetzee","doi":"10.4314/sajg.v8i2.12","DOIUrl":"https://doi.org/10.4314/sajg.v8i2.12","url":null,"abstract":"This study highlights the usage of deep learning artificial neural networks in the assessment of groundwater vulnerability of a coalfield. The network uses the DRIST model with parameters (depth to water level, recharge, impact of the vadose zone, soils and topographic slope) as training inputs and borehole sulphate concentration as training output. This technique was applied to Witbank coalfield, where acid mine drainage emanating from coal mining operations is a huge concern for surrounding environment and groundwater resources. The generated groundwater vulnerability model was validated with another sulphate dataset not used during model training. The deep neural network model with dropout and decaying learning rate regularisers correlated very well with sulphate data from another source as compared to the index and overlay DRIST model. The approach, differentiated areas in terms of vulnerability to acid mine drainage, which can aid policy, and decision makers to make scientifically informed decisions on land use planning. The approach developed in this research can be applied to other coalfields in order to evaluate its robustness to different hydrogeological and geological conditions.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2019-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41961544","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}
John Richard Otukei, Prossy Atolere, A. Gidudu, F. Martini
Information on deformation of the land surface is vital for planning of infrastructure especially in areas such as the Albertine graben with substantial amounts of oil discoveries. Traditionally, global positioning systems, precise leveling and geotechnical techniques have been used for assessing and monitoring ground deformations. While these techniques provide accurate information, they are point based, expensive, time consuming and labour intensive over large area monitoring. This study explored an interferometric synthetic aperture radar (InSAR) approach for mapping deformation over Buliisa oil discovery area located in the Western arm of the East African rift valley. The method was implemented by measuring the phase differences of ALOS PALSAR data acquired between 2007 and 2011. Deformation estimates varied between -0.45m to +0.34m while the mean displacements varied from –0.10m to 0.089m. High ground deformation was detected in the Southern, North Eastern and North Western parts contributed by agricultural activity and drilling pad constructions. Generally, analysis of ALOS PALSAR data using InSAR approach provides a viable option for assessing land surface deformation in Buliisa oil exploration area.
{"title":"Ground deformation assessment of the Albertine graben using inSAR","authors":"John Richard Otukei, Prossy Atolere, A. Gidudu, F. Martini","doi":"10.4314/sajg.v8i2.2","DOIUrl":"https://doi.org/10.4314/sajg.v8i2.2","url":null,"abstract":"Information on deformation of the land surface is vital for planning of infrastructure especially in areas such as the Albertine graben with substantial amounts of oil discoveries. Traditionally, global positioning systems, precise leveling and geotechnical techniques have been used for assessing and monitoring ground deformations. While these techniques provide accurate information, they are point based, expensive, time consuming and labour intensive over large area monitoring. This study explored an interferometric synthetic aperture radar (InSAR) approach for mapping deformation over Buliisa oil discovery area located in the Western arm of the East African rift valley. The method was implemented by measuring the phase differences of ALOS PALSAR data acquired between 2007 and 2011. Deformation estimates varied between -0.45m to +0.34m while the mean displacements varied from –0.10m to 0.089m. High ground deformation was detected in the Southern, North Eastern and North Western parts contributed by agricultural activity and drilling pad constructions. Generally, analysis of ALOS PALSAR data using InSAR approach provides a viable option for assessing land surface deformation in Buliisa oil exploration area.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2019-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48978561","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}
Landsat-8 OLI imagery of Sokoto, Nigeria, was processed to emphasize the geology features and mineral potential of the area. Band ratios were assigned to RGB. Band ratio highlights ferric ion minerals, emphasizes ferrous minerals, and distinguishes iron oxide minerals from carbonate minerals. In a second technique, band ratio was replaced with in order to accentuate clay minerals with high reflectance within band 7. The last technique evaluated in this study used spectral information from minimum noise fraction image to map surface geology. Supervised classification training sites were selected using five classes (clay, ironstone, alteration zone, water and vegetation). The band ratio classification using maximum likelihood classification was fairly accurate and matched the geologic map of the area, also showing an alteration zone that coincided with the migmatite-quartz/mica schist contact. The classified image was finally passed through a filtering effect for generalization of the data. This filtering effect was helpful in discriminating the pixels of ironstone and those of the alteration zone on the classified map.
{"title":"Application of remote sensing method for geological interpretation of Sokoto Plain, Nigeria","authors":"Aisabokhae Joseph, O. Bamidele","doi":"10.4314/SAJG.V7I3.12","DOIUrl":"https://doi.org/10.4314/SAJG.V7I3.12","url":null,"abstract":"Landsat-8 OLI imagery of Sokoto, Nigeria, was processed to emphasize the geology features and mineral potential of the area. Band ratios were assigned to RGB. Band ratio highlights ferric ion minerals, emphasizes ferrous minerals, and distinguishes iron oxide minerals from carbonate minerals. In a second technique, band ratio was replaced with in order to accentuate clay minerals with high reflectance within band 7. The last technique evaluated in this study used spectral information from minimum noise fraction image to map surface geology. Supervised classification training sites were selected using five classes (clay, ironstone, alteration zone, water and vegetation). The band ratio classification using maximum likelihood classification was fairly accurate and matched the geologic map of the area, also showing an alteration zone that coincided with the migmatite-quartz/mica schist contact. The classified image was finally passed through a filtering effect for generalization of the data. This filtering effect was helpful in discriminating the pixels of ironstone and those of the alteration zone on the classified map.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2019-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.4314/SAJG.V7I3.12","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44736908","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}
Good redundancy is required to isolate gross errors and improve the qualities of derived parameters. Improving the weak redundancies of traditional traverses by traversing on double lines is now possible with total stations which provide for less cumbersome measurements than previously possible and more so now that control traverses are computed by least squares adjustment using readily available computer software. Traversing on double lines requires some care in choosing traverse stations with inter-visibility from two immediately preceding and two directly succeeding stations. Traverses were run on double lines resulting in redundancy increase of seven per station. Local accuracy precision parameters improved also by as much as 25% and 52% with implementation at 30% and 100% of the traverse stations respectively. A chart that may be used to determine percentage number of traverse stations where traversing on double lines would be implemented to achieve set local accuracy improvements is presented.
{"title":"Improving traverse redundancy and precision by running on double lines","authors":"A. C. Chukwuocha, Franklin Enyinnaya Onyeagoro","doi":"10.4314/SAJG.V7I3.13","DOIUrl":"https://doi.org/10.4314/SAJG.V7I3.13","url":null,"abstract":"Good redundancy is required to isolate gross errors and improve the qualities of derived parameters. Improving the weak redundancies of traditional traverses by traversing on double lines is now possible with total stations which provide for less cumbersome measurements than previously possible and more so now that control traverses are computed by least squares adjustment using readily available computer software. Traversing on double lines requires some care in choosing traverse stations with inter-visibility from two immediately preceding and two directly succeeding stations. Traverses were run on double lines resulting in redundancy increase of seven per station. Local accuracy precision parameters improved also by as much as 25% and 52% with implementation at 30% and 100% of the traverse stations respectively. A chart that may be used to determine percentage number of traverse stations where traversing on double lines would be implemented to achieve set local accuracy improvements is presented.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2019-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.4314/SAJG.V7I3.13","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48226984","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}
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