The main aim of this paper is to demonstrate the mapping outputs of the historic core of Gonabad city based on both physical and nonphysical elements. Despite the fact that the architectural elements have been the main sources of data for the conservation of the historic part of cities, seemingly, the cognitive map based on the perceptions of the inhabitants could enhance the level of the reliability of the outputs. The methods of the research were designed based on the survey and interview to collect both physical and nonphysical data. The physical was included the current historical elements such as mosque, school, and water storage, and the nonphysical was included the destroyed elements such as the wall, gates, towers that have been part of the memories of the inhabitants. ArcGIS was applied for overlaying the data. The findings of the research identified that despite the architectural elements located in a specific location, perception of the people referred to the broader areas in terms of the historic area. As a conclusion, both historical areas of the city include a different pattern of the development. The physical and nonphysical elements played a significant role to highlight the historic core of the city. However, the cognitive map based on the perception of users is not fitted exactly with the geo-reference data, and it is more flexible in terms of conceptual forms. The result of the study represented the map of the historic cores of the city for conservation activity.
{"title":"Application of physical and nonphysical elements in the conservation of historic core of city","authors":"R. Tafahomi","doi":"10.4314/sajg.v10i1.6","DOIUrl":"https://doi.org/10.4314/sajg.v10i1.6","url":null,"abstract":"The main aim of this paper is to demonstrate the mapping outputs of the historic core of Gonabad city based on both physical and nonphysical elements. Despite the fact that the architectural elements have been the main sources of data for the conservation of the historic part of cities, seemingly, the cognitive map based on the perceptions of the inhabitants could enhance the level of the reliability of the outputs. The methods of the research were designed based on the survey and interview to collect both physical and nonphysical data. The physical was included the current historical elements such as mosque, school, and water storage, and the nonphysical was included the destroyed elements such as the wall, gates, towers that have been part of the memories of the inhabitants. ArcGIS was applied for overlaying the data. The findings of the research identified that despite the architectural elements located in a specific location, perception of the people referred to the broader areas in terms of the historic area. As a conclusion, both historical areas of the city include a different pattern of the development. The physical and nonphysical elements played a significant role to highlight the historic core of the city. However, the cognitive map based on the perception of users is not fitted exactly with the geo-reference data, and it is more flexible in terms of conceptual forms. The result of the study represented the map of the historic cores of the city for conservation activity.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2022-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47987649","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}
Heindrich du Plessis, H. Grobler, Curtis Mashimbye
The purpose of this paper is to investigate the geographical information science (GISc) competencies, knowledge, and skills required by practitioners working in the mining and exploration industries. The paper promotes the appropriate design of education programs including short learning programs (SLP) as well as emerging delivery mechanisms such as distance learning opportunities. Programs are submitted for quality control through certification and accreditation at quality control councils such as the Council for Higher Education (CHE), South African Qualifications Authority (SAQA) and the South African Geomatics Council (SAGC). The paper concludes with a proposed module composition that is still subject to further consultation and input from the mining industry.
{"title":"A review of GISc education, its value and use in the mining and exploration industries","authors":"Heindrich du Plessis, H. Grobler, Curtis Mashimbye","doi":"10.4314/sajg.v11i1.9","DOIUrl":"https://doi.org/10.4314/sajg.v11i1.9","url":null,"abstract":"The purpose of this paper is to investigate the geographical information science (GISc) competencies, knowledge, and skills required by practitioners working in the mining and exploration industries. The paper promotes the appropriate design of education programs including short learning programs (SLP) as well as emerging delivery mechanisms such as distance learning opportunities. Programs are submitted for quality control through certification and accreditation at quality control councils such as the Council for Higher Education (CHE), South African Qualifications Authority (SAQA) and the South African Geomatics Council (SAGC). The paper concludes with a proposed module composition that is still subject to further consultation and input from the mining industry.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2022-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41825370","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 paper estimates bare area gain detected using cloud free Landsat 7 (ETM+) and Landsat 8 (OLI) in Botswana. From 2002 to 2020, agricultural fields shrunk by 76.4%, while built-up increased by 49.2%, and bare areas increased from 3.32% to 7.03% (or 111.7%). There is a significant seasonal change in bare area detected reaching maximum during the dry season when there is little or no ground cover. In this study, the seasonality of bare area gain was overcome by only considering a bare area pixel to contribute to bare area gain if it exists during both the winter and summer months. The probability of bare area detection was 75.0% and probability of false detection 13.3% respectively. The 13% false detection tended to be built-up areas which had similar spectral characteristics as bare areas since most built-up areas have no ground cover. The bare area gain is driven by the high population growth rate of 3.4%. From 2001 to 2017, the population of the study area has increased by 34% and now accounts for 47% of the population of Botswana.
{"title":"Non-seasonal Landsat based bare area gain detection in Botswana during 2002 to 2020 Period using Maximum Likelihood Classifier (MLC).","authors":"R. Tsheko","doi":"10.4314/sajg.v11i1.7","DOIUrl":"https://doi.org/10.4314/sajg.v11i1.7","url":null,"abstract":"This paper estimates bare area gain detected using cloud free Landsat 7 (ETM+) and Landsat 8 (OLI) in Botswana. From 2002 to 2020, agricultural fields shrunk by 76.4%, while built-up increased by 49.2%, and bare areas increased from 3.32% to 7.03% (or 111.7%). There is a significant seasonal change in bare area detected reaching maximum during the dry season when there is little or no ground cover. In this study, the seasonality of bare area gain was overcome by only considering a bare area pixel to contribute to bare area gain if it exists during both the winter and summer months. The probability of bare area detection was 75.0% and probability of false detection 13.3% respectively. The 13% false detection tended to be built-up areas which had similar spectral characteristics as bare areas since most built-up areas have no ground cover. The bare area gain is driven by the high population growth rate of 3.4%. From 2001 to 2017, the population of the study area has increased by 34% and now accounts for 47% of the population of Botswana.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2022-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43873341","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}
Flood prediction is very important in land and water resources management. Many flood disasters could be mitigated with adequate preparedness especially in urban watershed. This study assessed the runoff potential of Opa watershed in Southwest Nigeria using remote sensing and the Soil Conservation Service or SCS curve number (CN) techniques. The 2007 NigSat image of the year 2007 was classified into different land cover classes and combined with its hydrological soil groups to determine the curve number of each sub-watershed. The sub-watershed with low curve number is considered to have lower runoff potential while the one with higher curve number is considered to have higher runoff potential. The CN was also used to estimate the potential maximum retention, (S) and potential runoff, (Q) for each sub-watershed using a rainfall event of 2-year return period in the watershed. The weighted runoff was used to determine sub-watersheds with highest and lowest runoff potential. The study showed that urban sub-watershed 9 with average CN value of 85.93 has highest weighted runoff potential (5.53 mm) while the vegetated sub-watershed 10 with average CN value of 69.46 has the lowest weighted runoff potential (0.34 mm). The study concluded that using available geospatial technology and appropriate hydrologic assessment techniques constitute an effective flood prediction method for disaster risk reduction and sustainable urban watershed management.
{"title":"Assessment of runoff potential for disaster risk reduction using geospatial technology in Opa watershed, Southwestern Nigeria","authors":"Orewole Maruf Oladotun","doi":"10.4314/sajg.v10i2.8","DOIUrl":"https://doi.org/10.4314/sajg.v10i2.8","url":null,"abstract":"Flood prediction is very important in land and water resources management. Many flood disasters could be mitigated with adequate preparedness especially in urban watershed. This study assessed the runoff potential of Opa watershed in Southwest Nigeria using remote sensing and the Soil Conservation Service or SCS curve number (CN) techniques. The 2007 NigSat image of the year 2007 was classified into different land cover classes and combined with its hydrological soil groups to determine the curve number of each sub-watershed. The sub-watershed with low curve number is considered to have lower runoff potential while the one with higher curve number is considered to have higher runoff potential. The CN was also used to estimate the potential maximum retention, (S) and potential runoff, (Q) for each sub-watershed using a rainfall event of 2-year return period in the watershed. The weighted runoff was used to determine sub-watersheds with highest and lowest runoff potential. The study showed that urban sub-watershed 9 with average CN value of 85.93 has highest weighted runoff potential (5.53 mm) while the vegetated sub-watershed 10 with average CN value of 69.46 has the lowest weighted runoff potential (0.34 mm). The study concluded that using available geospatial technology and appropriate hydrologic assessment techniques constitute an effective flood prediction method for disaster risk reduction and sustainable urban watershed management.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2022-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46058529","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}
Remote sensing and GIS are often used to assess spatiotemporal variations for land use/land cover (LULC) monitoring and classification. While LULC monitoring and classification has been undertaken in Eswatini, little attention has been given to ascertaining covered thematic areas, methods of image classification, and approaches and techniques for improving classification accuracy. This paper summarises and synthesizes the progress made in the Kingdom of Eswatini regarding the application of remote sensing and GIS in LULC monitoring and classification. Eight thematic areas (water resources mapping; land degradation; forestry; wildfire detection; urban expansion; crop production; disease surveillance; general mapping) dominate evaluated LULC studies, employing three LULC classification methods (classic; manual; advanced). While some studies include strengths and weaknesses of LULC classification techniques applied, others do not. This review shows that only two advanced classifiers (random forest; object-based) were identified from the reviewed articles. In addition, reviewed studies applied only two approaches (use of multi temporal data; fine spatial resolution data) and three techniques (use of ancillary data; post-classification procedure; the use of multisource data) for improving classification accuracy. Furthermore, the review finds that limited LULC investigations have been covered in Eswatini with a specific focus on the Sustainable Development Goals (SDGs). As such, this review recommends 1) the inclusion of higher resolution imagery for mapping purposes, 2) the adaptation of strengths and weaknesses for any image classification technique employed in future publications, 3) the use of more varied approaches and techniques for improving classification accuracy and area estimates, 4) inclusion of standard errors or confidence intervals for error-adjusted area estimates as part of accuracy assessment reporting, 5) the application of advanced image classifiers, and 6) the application of Earth Observation (EO) Analysis Ready Data (ARD) in the production of information for the support of the SDGs.
{"title":"The use of remote sensing and GIS for land use and land cover mapping in Eswatini: A Review","authors":"Sabelo P. Simelane, C. Hansen, C. Munghemezulu","doi":"10.4314/sajg.v10i2.13","DOIUrl":"https://doi.org/10.4314/sajg.v10i2.13","url":null,"abstract":"Remote sensing and GIS are often used to assess spatiotemporal variations for land use/land cover (LULC) monitoring and classification. While LULC monitoring and classification has been undertaken in Eswatini, little attention has been given to ascertaining covered thematic areas, methods of image classification, and approaches and techniques for improving classification accuracy. This paper summarises and synthesizes the progress made in the Kingdom of Eswatini regarding the application of remote sensing and GIS in LULC monitoring and classification. Eight thematic areas (water resources mapping; land degradation; forestry; wildfire detection; urban expansion; crop production; disease surveillance; general mapping) dominate evaluated LULC studies, employing three LULC classification methods (classic; manual; advanced). While some studies include strengths and weaknesses of LULC classification techniques applied, others do not. This review shows that only two advanced classifiers (random forest; object-based) were identified from the reviewed articles. In addition, reviewed studies applied only two approaches (use of multi temporal data; fine spatial resolution data) and three techniques (use of ancillary data; post-classification procedure; the use of multisource data) for improving classification accuracy. Furthermore, the review finds that limited LULC investigations have been covered in Eswatini with a specific focus on the Sustainable Development Goals (SDGs). As such, this review recommends 1) the inclusion of higher resolution imagery for mapping purposes, 2) the adaptation of strengths and weaknesses for any image classification technique employed in future publications, 3) the use of more varied approaches and techniques for improving classification accuracy and area estimates, 4) inclusion of standard errors or confidence intervals for error-adjusted area estimates as part of accuracy assessment reporting, 5) the application of advanced image classifiers, and 6) the application of Earth Observation (EO) Analysis Ready Data (ARD) in the production of information for the support of the SDGs.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2022-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45735197","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}
Tropospheric delay prediction models have become increasingly important in Global Navigation Satellite System (GNSS) as they play a critical role in GNSS positioning applications. Due to the different atmospheric conditions over the earth regions, tropospheric effect on GNSS signals also differs, influencing the performance of these prediction models. Thus, the choice of a particular prediction model can significantly degrade the positioning accuracy especially when the model does not suit the user’s environs. Therefore, a performance assessment of existing prediction models in various regions for a suitable one is very imperative. This paper evaluates and analyses seven commonly used tropospheric delay models in Ghana in terms of performances in Zenith Tropospheric Delay (ZTD) estimation and baseline positional accuracies using data from six selected Continuously Operating Reference Stations (CORS). The 1˚x1˚ gridded Vienna Mapping Functions 3 (VMF3) ZTD product and coordinates solutions from the CSRS-PPP positioning service were respectively used as references. The results show that the Black model performed better in estimating the ZTD, followed by Askne and Nordius model. The Saastamoinen, Marini and Murray, Niell, Goads and Goodman and Hopfield models respectively performed poorly. However, the result of the baseline solutions did not show much variation in the coordinate difference provided by the use of the prediction models, nonetheless, the Black and Askne and Nordius models continue to dominate the other models. Of all the models evaluated, either Black or Askne and Nordius model is recommended for use to mitigate the ZTD in the study area, however, the choice of the Black model will be more desirable.
{"title":"Comparative evaluation and analysis of different tropospheric delay models in Ghana","authors":"S. Osah, Akwasi Acheampong, I. Dadzie, C. Fosu","doi":"10.4314/sajg.v10i2.10","DOIUrl":"https://doi.org/10.4314/sajg.v10i2.10","url":null,"abstract":"Tropospheric delay prediction models have become increasingly important in Global Navigation Satellite System (GNSS) as they play a critical role in GNSS positioning applications. Due to the different atmospheric conditions over the earth regions, tropospheric effect on GNSS signals also differs, influencing the performance of these prediction models. Thus, the choice of a particular prediction model can significantly degrade the positioning accuracy especially when the model does not suit the user’s environs. Therefore, a performance assessment of existing prediction models in various regions for a suitable one is very imperative. This paper evaluates and analyses seven commonly used tropospheric delay models in Ghana in terms of performances in Zenith Tropospheric Delay (ZTD) estimation and baseline positional accuracies using data from six selected Continuously Operating Reference Stations (CORS). The 1˚x1˚ gridded Vienna Mapping Functions 3 (VMF3) ZTD product and coordinates solutions from the CSRS-PPP positioning service were respectively used as references. The results show that the Black model performed better in estimating the ZTD, followed by Askne and Nordius model. The Saastamoinen, Marini and Murray, Niell, Goads and Goodman and Hopfield models respectively performed poorly. However, the result of the baseline solutions did not show much variation in the coordinate difference provided by the use of the prediction models, nonetheless, the Black and Askne and Nordius models continue to dominate the other models. Of all the models evaluated, either Black or Askne and Nordius model is recommended for use to mitigate the ZTD in the study area, however, the choice of the Black model will be more desirable.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2022-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49177782","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}
The statistical qualities of census output areas are of great importance especially when the purpose of output areas is to understand the statistical properties of the population rather than mapping. If the purpose of creating census output areas is solely for displaying results in a map format, shape compactness of output areas is prioritised. In that case, other statistical characteristics such as population, population mean and social homogeneity are often ignored. This paper explored the statistical qualities of the Automated Zone-design Tool (AZTool) generated census output areas using the 2001 census Enumeration Areas (EAs) as building blocks in South Africa. The statistical qualities were mainly based on population target mean, minimum population threshold, social homogeneity as well as shape compactness. The homogeneity variables that were selected from the 2001 census data were dwelling type and geotype. The results showed that the AZTool generated output areas substantially outperformed the original EAs and Small Area Layers (SALs) in terms of the minimum population threshold and population distribution statistical qualities. It is worth noting though that the AZTool output areas were less compact and homogeneous than the original EAs in both urban and rural settings. The fact that a minimum population threshold of 500 was respected by the AZTool output areas in both rural and urban settings was a huge success from confidentiality point of view. It was concluded that the AZTool could be utilized to produce robust and high-quality optimised output areas for population census dissemination in South Africa.
人口普查产出地区的统计质量非常重要，特别是当产出地区的目的是了解人口的统计特性而不是绘图时。如果创建普查输出区域的目的仅仅是为了以地图格式显示结果，则优先考虑输出区域的形状紧凑性。在这种情况下，其他统计特征，如人口、人口均值和社会同质性往往被忽略。本文探讨了使用2001年南非人口普查枚举区(EAs)作为构建块的自动区域设计工具(AZTool)生成的人口普查输出区域的统计质量。统计质量主要基于人口目标均值、最小人口阈值、社会同质性和形状紧密性。从2001年人口普查数据中选取的同质性变量为居住类型和地理类型。结果表明，AZTool生成的输出区域在最小种群阈值和种群分布统计质量方面明显优于原始ea和Small Area Layers (SALs)。值得注意的是，AZTool的输出区域在城市和农村环境中都不如原来的ea紧凑和均匀。从保密性的角度来看，AZTool输出地区在农村和城市环境中都遵守了500人的最低人口门槛，这是一个巨大的成功。最后得出的结论是，可以利用人口普查工具为南非的人口普查传播提供可靠和高质量的最佳产出领域。
{"title":"The statistical qualities of the zone design census output areas","authors":"T. Mokhele, O. Mutanga, F. Ahmed","doi":"10.4314/sajg.v11i1.1","DOIUrl":"https://doi.org/10.4314/sajg.v11i1.1","url":null,"abstract":"The statistical qualities of census output areas are of great importance especially when the purpose of output areas is to understand the statistical properties of the population rather than mapping. If the purpose of creating census output areas is solely for displaying results in a map format, shape compactness of output areas is prioritised. In that case, other statistical characteristics such as population, population mean and social homogeneity are often ignored. This paper explored the statistical qualities of the Automated Zone-design Tool (AZTool) generated census output areas using the 2001 census Enumeration Areas (EAs) as building blocks in South Africa. The statistical qualities were mainly based on population target mean, minimum population threshold, social homogeneity as well as shape compactness. The homogeneity variables that were selected from the 2001 census data were dwelling type and geotype. The results showed that the AZTool generated output areas substantially outperformed the original EAs and Small Area Layers (SALs) in terms of the minimum population threshold and population distribution statistical qualities. It is worth noting though that the AZTool output areas were less compact and homogeneous than the original EAs in both urban and rural settings. The fact that a minimum population threshold of 500 was respected by the AZTool output areas in both rural and urban settings was a huge success from confidentiality point of view. It was concluded that the AZTool could be utilized to produce robust and high-quality optimised output areas for population census dissemination in South Africa.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2022-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42956130","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}
The implementation of Unmanned Aerial Vehicles (UAVs) and Structure-from-Motion (SfM) photogrammetry in assessing forest structures for forest inventory and biomass estimations has shown great promise in reducing costs and labour intensity while providing relative accuracy. Tree Height (TH) and Diameter at Breast Height (DBH) are two major variables in biomass assessment. UAV-based TH estimations depend on reliable Digital Terrain Models (DTMs), while UAV-based DBH estimations depend on reliable dense photogrammetric point cloud. The main aim of this study was to evaluate the performance of multi-rotor UAV photogrammetric point cloud in estimating homogeneous and heterogeneous forest structures, and their comparison to more accurate LiDAR data obtained from Aerial Laser Scanners (ALS), Terrestrial Laser Scanners (TLS), and more conventional means like manual field measurements. TH was assessed using UAVSfM and LiDAR point cloud derived DTMs, while DBH was assessed by comparing UAVSfM photogrammetric point cloud to LiDAR point cloud, as well as to manual measurements. The results obtained in the study indicated that there was a high correlation between UAVSfM TH and ALSLiDAR TH (R2 = 0.9258) for homogeneous forest structures, while a lower correlation between UAVSfM TH and TLSLiDAR TH (R2 = 0.8614) and UAVSfM TH and ALSLiDAR TH (R2 = 0.8850) was achieved for heterogeneous forest structures. A moderate correlation was obtained between UAVSfM DBH and field measurements (R2 = 0.5955) for homogenous forest structures, as well as between UAVSfM DBH and TLSLiDAR DBH (R2 = 0.5237), but a low correlation between UAVSfM DBH and UAVLiDAR DBH (R2 = 0.1114). The study demonstrated that UAV acquired imagery can be used to accurately estimate TH in both forest types, but has challenges estimating DBH. The research does not suggest that UAVSfM serves as a replacement for more high-cost and accurate LiDAR data, but rather as a cheaper adequate alternative in forestry management depending on accuracy requirements.
{"title":"Estimating the performance of multi-rotor unmanned aerial vehicle structure-from-motion (UAVsfm) imagery in assessing homogeneous and heterogeneous forest structures: a comparison to airborne and terrestrial laser scanning","authors":"Kenechukwu C. Onwudinjo, J. Smit","doi":"10.4314/sajg.v11i1.6","DOIUrl":"https://doi.org/10.4314/sajg.v11i1.6","url":null,"abstract":"The implementation of Unmanned Aerial Vehicles (UAVs) and Structure-from-Motion (SfM) photogrammetry in assessing forest structures for forest inventory and biomass estimations has shown great promise in reducing costs and labour intensity while providing relative accuracy. Tree Height (TH) and Diameter at Breast Height (DBH) are two major variables in biomass assessment. UAV-based TH estimations depend on reliable Digital Terrain Models (DTMs), while UAV-based DBH estimations depend on reliable dense photogrammetric point cloud. The main aim of this study was to evaluate the performance of multi-rotor UAV photogrammetric point cloud in estimating homogeneous and heterogeneous forest structures, and their comparison to more accurate LiDAR data obtained from Aerial Laser Scanners (ALS), Terrestrial Laser Scanners (TLS), and more conventional means like manual field measurements. TH was assessed using UAVSfM and LiDAR point cloud derived DTMs, while DBH was assessed by comparing UAVSfM photogrammetric point cloud to LiDAR point cloud, as well as to manual measurements. The results obtained in the study indicated that there was a high correlation between UAVSfM TH and ALSLiDAR TH (R2 = 0.9258) for homogeneous forest structures, while a lower correlation between UAVSfM TH and TLSLiDAR TH (R2 = 0.8614) and UAVSfM TH and ALSLiDAR TH (R2 = 0.8850) was achieved for heterogeneous forest structures. A moderate correlation was obtained between UAVSfM DBH and field measurements (R2 = 0.5955) for homogenous forest structures, as well as between UAVSfM DBH and TLSLiDAR DBH (R2 = 0.5237), but a low correlation between UAVSfM DBH and UAVLiDAR DBH (R2 = 0.1114). The study demonstrated that UAV acquired imagery can be used to accurately estimate TH in both forest types, but has challenges estimating DBH. The research does not suggest that UAVSfM serves as a replacement for more high-cost and accurate LiDAR data, but rather as a cheaper adequate alternative in forestry management depending on accuracy requirements.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2022-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47690129","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}
Aarifah Williams, J. Berkland, Bongeka Maphumulo, Gaathier Mahed, Keegan Stokes
We present the measurement of fractures near the town of Beaufort West, South Africa. A field visit was conducted to examine the dip and azimuth of rock outcrops in and around the town. The locations of these various fractures were mapped and their orientation, which included the dip and strike of the rock surface, was measured using a geological compass (i.e., Brunton Truarc 15 Compass). The geological compass measurements were then compared to three mobile devices. These mobile devices, namely an iPad 2 and two smartphones (Samsung S8 and Huawei P10 Lite), all had the same application for standardization and the mobile device results were individually compared to the geological compass. The data stemming from the various mobile devices and the geological compass were then compared in terms of their variance. This statistical analysis was performed using the Correlated T-test method, as well as the Pearson Correlation Coefficient formula. To visually examine the main fracture orientations, the data obtained using the geological compass was plotted on a rose diagram. Results show that the relationship between the geological compass and the mobile device readings had little to no correlation, when using both the correlation and t-tests as combined determinants. This highlights the importance of ensuring measurement accuracy in the field as well as instrument calibration in situ.
{"title":"Accuracy assessment of smart devices for Geoscience field mapping","authors":"Aarifah Williams, J. Berkland, Bongeka Maphumulo, Gaathier Mahed, Keegan Stokes","doi":"10.4314/sajg.v11i1.4","DOIUrl":"https://doi.org/10.4314/sajg.v11i1.4","url":null,"abstract":"We present the measurement of fractures near the town of Beaufort West, South Africa. A field visit was conducted to examine the dip and azimuth of rock outcrops in and around the town. The locations of these various fractures were mapped and their orientation, which included the dip and strike of the rock surface, was measured using a geological compass (i.e., Brunton Truarc 15 Compass). The geological compass measurements were then compared to three mobile devices. These mobile devices, namely an iPad 2 and two smartphones (Samsung S8 and Huawei P10 Lite), all had the same application for standardization and the mobile device results were individually compared to the geological compass. The data stemming from the various mobile devices and the geological compass were then compared in terms of their variance. This statistical analysis was performed using the Correlated T-test method, as well as the Pearson Correlation Coefficient formula. To visually examine the main fracture orientations, the data obtained using the geological compass was plotted on a rose diagram. Results show that the relationship between the geological compass and the mobile device readings had little to no correlation, when using both the correlation and t-tests as combined determinants. This highlights the importance of ensuring measurement accuracy in the field as well as instrument calibration in situ.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2022-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46405950","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}
Processing of Global Navigational Satellite System (GNSS) data forms the basis for the usage of differential systems for obtaining spatial data. All open sources or commercial software packages developed for data processing give specific details to suit the intended purpose of the software. To obtain a uniform format for submitted survey data, Survey and Mapping Division (SMD) in various jurisdictions have specified formats for data submission for all kinds of surveys. In this regard, “GNSS Ghana” Software (GGS), a GNSS standalone Windows-based application with a modern user-friendly interface was developed for geodetic applications such as, projection and datum transformation worldwide, GNSS data post-processing of Receiver Independent Exchange Format (RINEX) files, and generating reports to meet Ghana SMD reporting standards including cadastral computations and reports for submission. To assess the developed software, GNSS data from two International GNSS Service (IGS) stations (BJCO and YKRO) were processed using GGS and three other commercial software such as GNSS Solution Software (GSS), Spectrum Survey Software (SSS), and Leica Geo Office (LGO), and the positional results compared against the existing coordinate. The results revealed that the GGS outperformed the remaining three commercial software packages with a sub-meter level of accuracy. Further assessment was conducted on datum transformation using the coordinates of 21 existing geodetic control points in Ghana. Utilizing the 7-transformation parameters of Ghana, the results gave uncertainties of [0.10ft. ± 0.99ft.] in the eastings and [0.02ft. ± 1.61ft.] in the northings with a 99% confidence level.
{"title":"Development of GNSS software for Ghana Survey and Mapping Division","authors":"Gameti Charles, Acheampong Akwasi Afrifa, J. Ayer","doi":"10.4314/sajg.v11i1.10","DOIUrl":"https://doi.org/10.4314/sajg.v11i1.10","url":null,"abstract":"Processing of Global Navigational Satellite System (GNSS) data forms the basis for the usage of differential systems for obtaining spatial data. All open sources or commercial software packages developed for data processing give specific details to suit the intended purpose of the software. To obtain a uniform format for submitted survey data, Survey and Mapping Division (SMD) in various jurisdictions have specified formats for data submission for all kinds of surveys. In this regard, “GNSS Ghana” Software (GGS), a GNSS standalone Windows-based application with a modern user-friendly interface was developed for geodetic applications such as, projection and datum transformation worldwide, GNSS data post-processing of Receiver Independent Exchange Format (RINEX) files, and generating reports to meet Ghana SMD reporting standards including cadastral computations and reports for submission. To assess the developed software, GNSS data from two International GNSS Service (IGS) stations (BJCO and YKRO) were processed using GGS and three other commercial software such as GNSS Solution Software (GSS), Spectrum Survey Software (SSS), and Leica Geo Office (LGO), and the positional results compared against the existing coordinate. The results revealed that the GGS outperformed the remaining three commercial software packages with a sub-meter level of accuracy. Further assessment was conducted on datum transformation using the coordinates of 21 existing geodetic control points in Ghana. Utilizing the 7-transformation parameters of Ghana, the results gave uncertainties of [0.10ft. ± 0.99ft.] in the eastings and [0.02ft. ± 1.61ft.] in the northings with a 99% confidence level.","PeriodicalId":43854,"journal":{"name":"South African Journal of Geomatics","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2022-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41888211","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：