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South African Journal of Geomatics
Journal Prestige (SJR): 0.113

Number of Followers: 2

This is an Open Access Journal

Open Access journal
ISSN (Print) 2225-8531
Published by African Journals Online

[261 journals]

GIS time series mapping of the Ciskei homeland
- Authors: Salih Ali, Siddique Motala
  Pages: 216 - 221
  Abstract: This study reports on the creation and evaluation of a spatio-temporal mapping of the Ciskei, one of the so-called ‘Bantustans’ or ‘homelands’ located in South Africa. The Ciskei was created as a result of race-based legislation during the colonial and apartheid periods. Its geographical extent changed over time, and the spatial changes coincided with the promulgation of different legislation. Geographic Information Systems (GIS) technology was used to create a time series animation and a static map to display the spatial change of the Ciskei boundaries. Questionnaires and interviews were used to investigate two main aspects. The questionnaire’s purpose was to investigate and compare map-readers’ cognition at detecting change between static and animated maps. Interviews allowed the researchers to qualitatively assess the value of such an exercise. Both the animated and static maps have advantages over each other but neither one of them has an overall clear advantage, confirming previous research. There is value of such mapping to decision-makers in government, as such an exercise can contribute to a more nuanced understanding of legislative, cadastral, planning and historical effects.
  PubDate: 2019-02-26
  DOI: 10.4314/sajg.v7i3.1
  Issue No: Vol. 7, No. 3 (2019)
Review of the use of remote sensing for monitoring wildfire risk
conditions to support fire risk assessment in protected areas
- Authors: Olga Dipuo Molaudzi, Samuel Adewale Adelabu
  Pages: 222 - 242
  Abstract: Fire risk assessment is one of the most important components in the management of fire that offers the framework for monitoring fire risk conditions. Whilst monitoring fire risk conditions commonly revolved around field data, Remote Sensing (RS) plays key role in quantifying and monitoring fire risk indicators. This study presents a review of remote sensing data and techniques for fire risk monitoring and assessment with a particular emphasis on its implications for wildfire risk mapping in protected areas. Firstly, we concentrate on RS derived variables employed to monitor fire risk conditions for fire risk assessment. Thereafter, an evaluation of the prominent RS platforms such as Broadband, Hyperspectral and Active sensors that have been utilized for wildfire risk assessment. Furthermore, we demonstrate the effectiveness in obtaining information that has operational use or immediate potentials for operational application in protected areas (PAs). RS techniques that involve extraction of landscape information from imagery were summarised. The review concludes that in practice, fire risk assessment that consider all variables/indicators that influence fire risk is impossible to establish, however it is imperative to incorporate indicators or variables of very high heterogeneous and “multi-sensoral or multivariate fire risk index approach for fire risk assessment in PA.Keywords: Protected Areas, Fire Risk conditions; Remote Sensing, Wildfire risk assessment
  PubDate: 2019-02-26
  DOI: 10.4314/sajg.v7i3.2
  Issue No: Vol. 7, No. 3 (2019)
Validation of satellite soil moisture in the absence of in situ soil
moisture: the case of the Tropical Yankin Basin
- Authors: Djigbo F. Badou, Bernd Diekkrüger, Carsten Montzka
  Pages: 243 - 256
  Abstract: Soil moisture is known to be important in hydrology, agronomy, flood and drought forecasting. Acquisition of in situ soil moisture data is time consuming, costly, and does not cover the scale required for basin analysis. The consideration of remotely-sensed soil moisture is therefore promising. However, considering the limitations of satellite data, there is a need to check their validity prior to their utilization for impact studies. This, in turn, poses a problem in the absence of in situ soil moisture. The present study suggests a methodology for testing the validity of remotely-sensed soil moisture without in situ soil moisture. Hydrological models with a detailed soil moisture routine are calibrated and validated with measured stream flows. The most behavioural solutions of modelled soil moistures are averaged, and used as proxy measurements. This methodology was applied to the Yankin Basin (8,171 km2), a tributary of the Niger River Basin. The soil moistures of three hydrological models (UHP-HRU, SWAT and WaSiM) used as proxy were compared with the daily ESA-CCI soil moisture for a four year period (2005-2008). The coefficient of determination (R2), bias and visual inspection were used as quality criteria. A rather small bias ranging from -0.01cm3/cm3 (SWAT & UHP-HRU) to -0.04cm3/cm3 (WaSiM &UHP-HRU) was determined as well as good R2 varying between 0.71 (SWAT & UHP-HRU) and 0.81 (WaSiM & SWAT & UHP-HRU). The ESA-CCI soil moisture was therefore judged as reliable for the study area. More important, this research shows that averaging soil moistures from different hydrological models provides valuable proxy measurements for testing the reliability of satellite soil moistures.
  PubDate: 2019-02-26
  DOI: 10.4314/sajg.v7i3.3
  Issue No: Vol. 7, No. 3 (2019)
The application of an Urban Sprawl Index: comparing towns and cities in
the Western Cape Province, South Africa
- Authors: Anele Horn, Amanda Van Eeden
  Pages: 257 - 267
  Abstract: The incidence and effects of urban sprawl have been the subject of a great many academic research mainly as a result of the challenges posed by continued urbanisation, especially in developing countries (see inter alia Jenks, Kozak and Takkanon 2008; Mander, Brebbia and Tiezzi 2006; Jenks and Burgess 2000; and Soja 2000). South Africa witnessed a proliferation of legislation and spatial policies to limit urban sprawl and contain the physical expansion and development of urban areas during the last two decades in response to exponential post-apartheid urbanization. In 2005, the Provincial Spatial Development Framework of the Western Cape Province, South Africa stated that “an Urban Edge shall be drawn around all villages, towns and cities in the province with the primary function to contain outward growth of urban settlements” (City of Cape Town, 2009) and in parallel the Provincial Department of Environmental Affairs and Development Planning published the Western Cape Urban Edge Guideline document assisting all municipalities in the province to delineate urban edges to be included in municipal Spatial Development Frameworks (SDF) thereby illustrating intent on maintaining urban footprints that are compact and limit developments that could be considered urban sprawl. Subsequently municipal urban edges have been delineated and are presently reflected in most municipal Spatial Development Frameworks in the province. This paper presents an Urban Sprawl Index as a tool to comparatively analyse the extent of urban sprawl between cities and towns of different sizes, making use of cadastre, land use and population data over time. The Urban Sprawl Index (USI) for the Western Cape put forward by this research will enable the comparative measurement of the extent of urban sprawl proportionately between the Metropolitan and local municipalities in the province and thereby aid in understanding the impact of planning instruments such as urban edges in the context of development dynamics and pressures experienced by individual cities.
  PubDate: 2019-02-26
  DOI: 10.4314/sajg.v7i3.4
  Issue No: Vol. 7, No. 3 (2019)
Extraction of low cost houses from a high spatial resolution satellite
imagery using Canny edge detection filter
- Authors: Naledzani Mudau, Paidamoyo Mhangara
  Pages: 268 - 278
  Abstract: Since its democratic dispensation in 1994, the South African government enacted a number of legislative and policy interventions aimed at availing equal housing opportunities to the previously marginalized citizens. Mismanagement and unreliable reporting has been widely reported in publicly funded housing programmes which necessitated the government to audit and monitor housing development projects in municipalities using more robust and independent methodologies. The objective of this study was therefore to test and demonstrate the effectiveness of high spatial resolution satellite imagery in validating the presence of government funded houses using an object-oriented classification technique that applies a Canny edge detection filter. The results of this study demonstrate that object-orientated classification applied on pan-sharpened SPOT 6 satellite imagery can be used to conduct a reliable inventory and validate the number of houses. The application of the multi-resolution segmentation and Canny edge detection filtering technique proved to be an effective means of mapping individual houses as shown by the high detection accuracy of 99% and quality percentage of 96%.Keywords: Houses, Remote Sensing, SPOT 6, Canny edge detection, Multi-resolution Segmentation, Object-Oriented Classification
  PubDate: 2019-02-26
  DOI: 10.4314/sajg.v7i3.5
  Issue No: Vol. 7, No. 3 (2019)
Estimating potential future (2030 and 2040) land use in the Bonsa
catchment, Ghana, West Africa
- Authors: Michael S. Aduah, M.L. Toucher, G.P.W. Jewitt
  Pages: 279 - 291
  Abstract: This study combined logistic regression, Markov chain and the Dyna-CLUE models to simulate land use patterns in the Bonsa catchment of Ghana, West Africa. Historical model validation produced Relative Operating Characteristics (ROC) statistics above 0.69; indicating a significant relationship between the driving factors and the land cover types, and overall accuracy of 71% as well as a Kappa statistic of 55%, indicating a moderate agreement between observed and simulated land uses. The statistics of the historical model were used to simulate three plausible future land use scenarios. The historical simulation revealed that increases in population density, proximity to roads and expansion of mines were the major drivers that significantly increased the probability of settlement expansion and deforestation. Simulations of future land use showed that settlement expansion and deforestation may increase by similar margins for all scenarios, but the increase in secondary forests may be higher for the economic growth and reforestation (EGR) scenario, compared to the economic growth (EG) and the business-as-usual (BAU) scenarios. The mining areas may double in the future for all the scenarios, but shrubs/farms may increase in the BAU scenario, but reduce marginally in the EG and the EGR scenarios. The results of this study can be used to support land use planning and evaluation of the impacts of different future development pathways.Keywords: Bonsa catchment, deforestation, driving factors, Dyna-CLUE, land use, logistic regression, West Africa
  PubDate: 2019-02-26
  DOI: 10.4314/sajg.v7i3.6
  Issue No: Vol. 7, No. 3 (2019)
A method for connecting traverses to GNSS controls eliminating troublesome
short GNSS orientation lines
- Authors: Akajiaku C. Chukwuocha
  Pages: 292 - 303
  Abstract: Global Navigation Satellite System (GNSS) surveys are used to establish long baseline control networks. Further breaking down of the controls are accomplished using total station traversing connected to the GNSS networks. Auxiliary stations are established at relatively short distances to each GNSS main station for traverse azimuth orientation. If the GNSS azimuth reference lines are short, the allowable uncertainties in the GNSS determined coordinates heavily encumber the accuracies of the azimuths derived from them. This is the problem with connecting traverses to GNSS controls via azimuth reference lines that are short. Reorientation traversing can solve the short GNSS azimuth reference line problem by running control traverses linked to GNSS controls without referencing the short GNSS azimuth lines. Four reorientation traverses of total traverse lengths of 1.4Km to 5.1Km were run between GNSS network stations to demonstrate the validity of the new method. A corresponding traditional traverse was run to compare with each of the reorientation traverse cases. Some t-distribution tests established that there were no statistical differences between the coordinates determined by the reorientation traverses and the corresponding traditional traverses coordinates at the 99% confidence level. P-value tests revealed that there were no significant probabilities of an extreme occurrence in which the coordinates from the two methods of traversing may be statistically different at the P < 0.01 confidence level. The research results thus show that reorientation traversing is a valid procedure that may be used to avoid the use of short GNSS reference lines.Keywords: Global Navigation Satellite Systems (GNSS), Reorientation Traversing, Azimuth, Controls
  PubDate: 2019-02-26
  DOI: 10.4314/sajg.v7i3.7
  Issue No: Vol. 7, No. 3 (2019)
Network database design for conflict and post-conflict Land Tenure
Information Systems (LTIS)
- Authors: Alaa Dabboor, Michael Barry
  Pages: 304 - 318
  Abstract: The paper presents the Talking Titler Network (TTN) database design for land records in complex situations. In conflict and post-conflict situations, conventional land record database models are limited in how they can handle the complex constellations of interests in particular land units. One solution is a network database model that can capture multiple, overlapping and layered tenure relationships in a changing environment which can be augmented by data mining and social network analysis to overcome the limitations of the relational data model in handling complex, competing evidence. The Triple Store graph database development system and its ontology languages were used to design and develop the TTN prototype. The authors’ observations from the Gaza Strip, an ongoing conflict situation, and Somaliland, a post-conflict situation, were used as illustrative contexts. The test results show that graph database flexibly captured, described, and automatically revealed tenure patterns. TTN simplified the complexity of tenure relationships among objects by organizing them into sets of connected triples, revealing tenure relationships, and visualizing tenure information as a graph network, and as a table. The initial design shows promise in capturing and revealing relationships in complex, contested tenure scenarios.
  PubDate: 2019-02-26
  DOI: 10.4314/sajg.v7i3.8
  Issue No: Vol. 7, No. 3 (2019)
Evaluating the effects of leaf characteristics on spectral signatures of
savannah woody species on remotely sensed imagery
- Authors: Chris Munyati, Lebo Eneth Malomane, Oupa Ermos Malahlela
  Pages: 319 - 330
  Abstract: Woody species on savannahs provide nutrition to wildlife and livestock ungulates. Understanding of woody leaf reflectance would benefit the application of remote sensing in analysis of these rangelands. This study sought to establish the influence of the leaf characteristics of size (leaf form) and chlorophyll content on the spectral reflectance characteristics of savannah woody species. The ability of optical remotely-sensed imagery to identify these two leaf characteristics and use them to determine the woody content of savannahs was then assessed. Two species that represented narrow leaf and broad leaf savannah woody species were studied: Acacia tortilis (renamed Vachellia tortilis) and Ziziphus mucronata, respectively. Forty seven woody individuals representing these species were sampled in north-western South Africa. Chlorophyll content, leaf area index (LAI) and spectral reflectance were determined in-situ using a chlorophyll meter, a canopy analyser and spectroradiometer, respectively. A SPOT 6 NAOMI image acquired at a time of year when grass reflectance was excluded from the spectral signature of non-senescent vegetation was used. The image data were converted to reflectance (%), and the green and near infrared (NIR) reflectance of the field-sampled trees on the image were correlated with the in-situ data. The results showed that the woody species differed significantly in their chlorophyll content and green reflectance, but only the NIR reflectance of the broad leaf species correlated strongly with a leaf characteristic, LAI. From the results it is concluded that LAI is the more reliable leaf characteristic for analysing the characteristics of savannahs in terms of woody content.
  PubDate: 2019-02-26
  DOI: 10.4314/sajg.v7i3.9
  Issue No: Vol. 7, No. 3 (2019)
Conformity assessment to development plan implementation as a tool for
development control in Kisii Town, Kenya
- Authors: Wilfred Ochieng Omollo
  Pages: 331 - 344
  Abstract: The objective of this study was to determine if the current land use development patterns in Kisii Town conformed to development zones in approved 1972 Kisii Town Physical Development Plan. Spatio-temporal analysis guided by Object Based Image Analysis (OBIA) was undertaken using QGIS software, integrating satellite image epochs of 2005, 2010 and 2017. Results showed that all approved development zones were not conformed to by ensuing land use development patterns, thus denoting nonconformity. The study also tested the hypothesis that there was no statistically significant difference between approved land use development patterns in the 1972 Kisii Town Physical Development Plan and ensuing land use development patterns in 2017. The test however found a significant difference between the two paired samples (M = 43.555, SD = 34.661) and (M = 36.344, SD = 34.047), t (9) = 4.03, p = 0.003. The null hypothesis was as a result rejected at 95% confidence level. The study concluded that because conformity to the development plan declined by a mean of 7.206, its objective as a tool for development control in Kisii Town was not attained. Recommendation was made that since the plan is outdated, a comprehensive plan covering the entire town should be prepared to provide a framework for development control. Additionally, there is need to adopt a strict enforcement and monitoring regime that ensures compliance with the plan.Keywords: Conformity, physical development plan, development control, Kisii Town
  PubDate: 2019-02-26
  DOI: 10.4314/sajg.v7i3.10
  Issue No: Vol. 7, No. 3 (2019)
The mapping and investigation of radionuclide pollution in the processing
plant of a spent phosphate mine by using GIS techniques
- Authors: Jacques Bezuidenhout
  Pages: 345 - 359
  Abstract: The mining and refinement of phosphate is characterised by high levels of uranium. An in situ gamma ray survey was done at the processing plant of a spent phosphate mine near Vredenburg on the west coast of South Africa in order to assess radionuclide concentrations. The concentrations of potassium, thorium and radioactive progeny of uranium were measured and plotted with the help of QGIS software. The results demonstrated high concentrations in specific areas of the plant. The highest concentrations were found to be 898 Bq/kg for potassium, 162 Bq/kg for 232Th and 639 Bq/kg for 226Ra. It was demonstrated that the refinement process technologically enhanced the naturally occurring radioactive nuclides and contaminated sections of the processing plant. The causes of the contamination were also investigated. The effective dose for the various parts of the processing plant was also estimated and the highest level was found to be 0.45 mSv/y. The article finally draws conclusions as to the environmental impact of the radiation and possible future preventative measures that could be followed in order to minimize pollution.Keywords: Environmental pollution, GIS techniques, Gamma ray measurements, uranium, phosphate mining
  PubDate: 2019-02-26
  DOI: 10.4314/sajg.v7i3.11
  Issue No: Vol. 7, No. 3 (2019)
Application of remote sensing method for geological interpretation of
Sokoto Plain, Nigeria
- Authors: Aisabokhae Joseph, Oresajo Bamidele
  Pages: 360 - 371
  Abstract: Landsat-8 OLI imagery of Sokoto, Nigeria, was processed to emphasize the geology features and mineral potential of the area. Band ratios (4/2,5/6,6/7) were assigned to RGB. Band ratio 4/2 highlights ferric ion minerals, 5/6 emphasizes ferrous minerals, and 6/7 distinguishes iron oxide minerals from carbonate minerals. In a second technique, band ratio 6/7 was replaced with 7/5 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. This study shows the distribution of classified earth-surface materials in Sokoto plain with the aid of supervised classification of Landsat-8 multispectral bands interpreted to reflect in-situ features.Keywords: Landsat-8 imagery, Sokoto, mineral potential, supervised classification
  PubDate: 2019-02-27
  DOI: 10.4314/sajg.v7i3.12
  Issue No: Vol. 7, No. 3 (2019)
Improving traverse redundancy and precision by running on double lines
- Authors: Akajiaku Chukwunyere Chukwuocha, Franklin Enyinnaya Onyeagoro
  Pages: 372 - 383
  Abstract: Good redundancy is required in measured quantities 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 to two immediately preceding and two directly succeeding stations from the instrument station. 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.Keywords: traverse, redundancy, precision, total station, control surveys, traversing on double lines, gross errors
  PubDate: 2019-02-27
  DOI: 10.4314/sajg.v7i3.13
  Issue No: Vol. 7, No. 3 (2019)