OpenUCT :: Browsing by Department "Division of Geomatics"

Browsing by Department "Division of Geomatics"

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Open Access
3D visualisation of the laetoli footprints on the internet
(2000) Taylor, Simon
Bibliography: p. 84-86.
Open Access
Afrikaner Nationalism and the Production of a White Cultural Heritage: An analysis of selected works undertaken by Dirk Visser and Gabriel Fagan from 1967-1993
(2012) Darke, Nicola Susan; Townsend, Stephen S
This dissertation entitled The Afrikaner Nationalism and the Production of a White Cultural Heritage: An analysis of selected works undertaken by Dirk Visser and Gabriel Fagan from 1967-1993 examines the construct of a white settler heritage as promoted and implemented through various restorations and reconstructions of DutchNOC buildings. The primary rationale of this study is to critically assess the actions of the main protagonists in the creation of this heritage, that is, the Department of Public Works, the National Monuments Council, Anton Rupert (and his Historic Homes of South Africa), the Simon van der Stel Foundation, the Institute of South African Architects and the provincial institutes. Directly related to this issue is the assessment as to whether the isolationist nature of the South Africa contributed to the plethora of stylistic restoration and reconstructions undertaken during the apartheid era. This study comprises two sections: first, the examination of the intellectual theoretical texts of Foucault, Nora and others pertaining to power, ideology, history and memory, as well as the seminal texts of Jokilehto and Choay which discuss the stylistic and historicist conservation theories of Viollet-le-Duc; and second, the analysis of selected case studies undertaken by Fagan on behalf of the state (The Castle of Good Hope and De Tuynhuys) and Visser on behalf of Rupert and Historic Homes of South Africa (Drostdy of Graaff-Reinet).
Open Access
Algorithms and design aspects of an automated vision based 3-D surface measurement system
(1995) Van der Vlugt, Graeme; Rüther, Heinz
This thesis reports on the investigation, development and implementation of digital/photogrammetric algorithms into a compatible system for measuring surfaces. Each of the important stages of such a measurement are dealt with in the text. Specifically, these include camera calibration, free network adjustment, location and centering of circular targets, orientation determination, the matching and measuring process and handling of results. The chosen algorithms (existing, modified and/or developed in this work) were all incorporated/designed to form an efficient and usable surface measurement system. Of particular importance was the investigation of determining conjugate (matching) surface points in the multiple images. In this respect a novel multi-image correlation search procedure was designed, implemented and tested. This algorithm provides high accuracy matching methods with suitably close provisional matching positions. A series of tests was carried out to study the performance of the algorithm and the results are presented in this work. Most notable was the method's high reliability when using more than two images, even in image areas with highly repetitive patterns. Multi-image correlation is considerably more robust than "traditional" stereo-correlation procedures. Other system tests performed included: tests on the stability of projected light from two off-the shelf projection devices; a test on the effect of PLL synchronisation of the camera-framegrabber combination of the images; tests on the accuracy performance of different centering techniques and surface measurements themselves. It was found that the off-the-shelf slide projector tested did not provide a stable projection, however an overhead projector which was warmed up for over an hour provided a suitably stable projection. The PLL synchronisation of the camera-framegrabber system produced a noticeable line-jitter (between sequential images) reaching over 0.1 pixels in the most badly affected lines. In a simulated test with artificial targets, template matching obtained the most accurate centre coordinates, however the much faster weighted centre of gravity with grey value as weight technique also provides highly accurate results. These two centering techniques agreed to 1/100th of a pixel when centering with real targets. The much faster centroiding technique is thus highly recommended for any application which requires high processing speeds (such as with on-line systems). Surface measurement precisions of 5/100th mm in the plane of the surface and 15/100th mm in depth were achieved in the measurements of the test objects. These objects all had similar dimensions with a diagonal of about 250mm in length. These accuracies could be substantially improved with higher resolution cameras and more images. Together, the algorithms presented in this work formed a surface measurement software program. The success of many of these algorithms, such as the target location method, and the semi-automatic point identification and exterior orientation determination procedure, could not be gauged with results as such, but by their successful incorporation into the system as properly functioning units.
Open Access
Analysis of photogrammetrically-derived digital surface and terrain models for building recognition
(1997) Mtshatsha, Bandile; Mason, Scott
Buildings are one of the most frequently occurring man-made objects and in urban scenes their detection and reconstruction, e.g., in the form of three-dimensional CAD (computer aided design) models, is very important to many users such as architects, town planners and telecommunications and environmental engineers. This thesis examines the role of digital terrain and surface models in supporting this reconstruction process. The thesis is structured into four main parts, namely, image matching to derive the data sets, building detection to delineate buildings from other man-made objects in DSM (digital surface model), DSM quality analysis to determine the reliability of the data, hydrological analysis to determine flood zones as an additional example of DTM application and finally conclusions and possible future outlook. Image matching was performed using an in-house image matching software in the Geomatics department. Off-the-shelf GIS functionality was used to tackle building detection, DSM quality analysis and hydrological analysis. A key feature of GIS functionality is the ability to exploit standard functions for the input/output, management, spatial analysis, editing and visualisation. It also aims at enhancing the accessibility of developed tools to end users.
Open Access
Assessing customary land administration systems for peri-urban land in Ghana
(2013) Akrofi, Emmanuel Offei; Augustinus, Clarissa
Customary tenure is the predominant land tenure system in Ghana. It has been practiced for many years. Customary land tenure is built on the foundations of an African concept of land, distinguished by centrality of community, spirituality, and mutual dependence of the individual and the community. Colonization, increased population, rapid urbanisation has placed enormous pressure on customary tenure, especially in peri-urban areas. This study investigates customary administration in peri-urban Ghana. Using critical realism and multimethodology, peri-urban customary tenure in Accra and Kumasi, the fastest growing cities in Ghana, are assessed. A model for assessing functionality for peri-urban customary systems has been developed. The results indicate that functional customary systems adhere to the principles of good governance in customary land administration, although a lot needs to be done to improve accountability, transparency and land rights of women. It was also observed that whether the system has patrilineal or matrilineal inheritance does not have any significant influence on functionality. Further research is recommended to investigate best practices from other tenure systems to improve peri-urban customary tenure without compromising good aspects of customary systems.
Open Access
A camcorder-based rapid mapping system
(1997) Motala, Siddique
This thesis reports on investigations into the potential of off-the-shelf camcorder imagery for rapid mapping. Video technology was chosen as it has the advantage of continuous image capture, enabling quick acquisition times in environments where access may be limited. Video imagery is also very low cost compared to metric photography, and has the advantage of on-line control of the photography, which, for applications with low to medium mapping accuracies, make it an attractive and cheap alternative, well suited for application in developing countries and dynamic environments. Two case studies are presented. In the first, Hi-8 camcorder imagery was acquired for informal settlement mapping under the UrbanModeler project being run by the Department of Geomatics at the University of Cape Town. The informal settlement of Marconi Beam in Milnerton, Cape Town serves as an application for the UrbanModeler project, whose objective is the development of image exploitation tools for automating the geo-spatial modeling of urban settlements, primarily informal (or "squatter") settlements. Rapid production of georeferenced mosaics from the video imagery is reported on, and these mosaics were used in conjunction with a GIS database of Marconi Beam. This GIS database, containing an inventory of shacks and occupants of the settlement, would ultimately help in relocating the occupants of Marconi Beam to Joe Slovo Park, a low cost formal housing settlement nearby. An analysis of the mapping potential of this data source is made with respect to image interpretability, and three-dimensional point positioning accuracy. The second case study lies in the terrestrial photogrammetry domain, in a joint project between the Department of Geomatics and the Department of Archaeology at the University of Cape Town. In June 1996, the fieldwork for the photogrammetric mapping of a newly discovered shipwreck was carried out. A Sony Hi-8 camcorder was used for video image capture, and control for the imagery was obtained by a combination of GPS and theodolite survey. Retroreflective targets were placed along the surface of the wreck to tie the imagery together. This thesis reports on the mapping of one of the sections of the shipwreck, and discusses the use of video imagery for the production of surface maps.
Open Access
Conceptual design of a GIS-based land inventory model for urban informal settlement land management
(2000) Yirenkyi, Samuel Yaw; Barry, Michael
Bibliography: leaves 77-82.
Open Access
Contemporary interventions in historic fabric: context and authenticity in the work of Gabriel Fagan
(2011) Scurr, Michael John; Townsend, Stephen S
This study focuses on three projects by Gabriel Fagan, one of South Africa’s most respected and awarded architects, namely The Dias Museum in Mossel Bay, the SA Breweries Visitor’s Centre in Newlands and the University of Cape Town’s Institute of Infectious Disease and Molecular Medicine. These projects are all essentially contemporary interventions in historic fabric and each contains easily identifiable and iconic new portions – the sail-like roof of the Dias Museum, the glass lift shaft at SAB and the circular glazed pavilion at UCT’s Medical School.
Open Access
Context based detection of urban land use zones
(2011) Louw, Johan; Sithole, George
This dissertation proposes an automated land-use zoning system based on the context of an urban scene. Automated zoning is an important step toward improving object extraction in an urban scene.
Open Access
Creating 3D models of cultural heritage sites with terrestrial laser scanning and 3D imaging
(2012) Held, Christoph; Rüther, Heinz; Smit, Julian
The advent of terrestrial laser-scanners made the digital preservation of cultural heritage sites an affordable technique to produce accurate and detailed 3D-computermodel representations for any kind of 3D-objects, such as buildings, infrastructure, and even entire landscapes. However, one of the key issues with this technique is the large amount of recorded points; a problem which was even more intensified by the recent advances in laser-scanning technology, which increased the data acquisition rate from 25 thousand to 1 million points per second. The following research presents a workflow for the processing of large-volume laser-scanning data, with a special focus on the needs of the Zamani initiative. The research project, based at the University of Cape Town, spatially documents African Cultural Heritage sites and Landscapes and produces meshed 3D models, of various, historically important objects, such as fortresses, mosques, churches, castles, palaces, rock art shelters, statues, stelae and even landscapes.
Open Access
Design of a communal land tenure information system for Namibia
(1999) Danso, Antwi Adjei; Barry, Michael B
This thesis describes some of the communal land tenure systems pertaining to Namibia. Understandably, lands held under communal land tenure have tended to be neither fully documented nor legally and explicitly formalised; communal land tenure systems have been through the mercy of arbitrary action by the state, private individuals or other institutions (S.A Government, 1996: 43). The study attempts to examine the issues involved in the design of a communal land tenure information system for Namibia. It therefore seeks to examine the possibility of using information technology to plan and manage customarily held land, the requirement for an effective design and implementation of such a system and the method of designing such an information system to make room for continual improvement and the addition of finer detail. The research begins with an in-depth literature review of the communal land tenure systems in Namibia and a description of similar information systems. This is followed by the research methodology, which describes the technique used for collecting, analysing and presenting the results of the study. The needs analysis and the data structure contained in the atlas are outlined. The fundamental concepts of database design and the various steps taken by the author to design and construct the land tenure database model for the dissertation are also discussed. The pilot project is analysed, taking into account the capability of the system, its success in terms of a needs analysis, and the adequacy of the data. It specifically analyses the design in the light of social relationships, person or group interests and the spatial component of communal land tenure systems with respect to each area. In addition, it seeks to answer the question whether the tool fits the communal land tenure system, discusses the strengths and weaknesses of the overall system design and the implementation strategies. It is envisaged that, with the provision of the information system in union with its database, this will help to identify and document a communal land tenure system. For the rural dweller or farmer, this system will provide a pictorial image of what is really happening on the ground. The information system could later be upgraded and fully implemented, enabling individuals to effectively plan activities around the existing circumstances and conditions. The recommendation that came out from the study was that given the limited information available on communal land tenure systems, more effort should be spent to study and gather data on the system. It is strongly recommended, therefore, that research into conditions in the communal areas be regarded as a top pri01ity by the Government of Namibia. This could lead to a richer information base in the communal areas to be utilised to improve the lifestyle of the rural communities. Thus, the prototype project designed in this thesis should be implemented fully and later developed and incorporated into an information system which, in the past, has lacked communal land tenure input. The research could not touch on all the communal land tenure areas in Namibia. It is therefore advised that the rest should be investigated in more detail. The inheritance and conflict resolution mechanism which were not modelled effectively should also be reinvestigated.
Open Access
The development of a method for semi-automatic classification of built-up areas from aerial imagery
(2013) Duncan, Patricia; Smit, Julian
It is essential for geospatial and mapping organisations that changes to the landscapeare regularly detected and captured, so that map databases can be updated. The Chief Directorate of National Geospatial Information (CD: NGI), South Africa’s national mapping agency, currently relies on manual methods for digitizing features and detecting changes. These methods are time consuming and labour intensive, and rely on the skills and interpretation of the operator. It is therefore necessary to move towards more automated methods in the production process at CD: NGI. The objective of this research is to develop a process for semi-automatic classification of built-up areas from aerial imagery in South Africa. Built-up areas are important as they can grow and change rapidly. Since the South African landscape is varied and climatological conditions differ from one area to another, a general and robust method that can be applied across the country is needed. This project aims to find the best approach for classifying urban built-up areas from high-resolution aerial imagery by comparing various image classification methods, so that a method that is transferable and applicable in diverse South African scenes may be developed. Image classification methods were compared and it was found that pixel-based classifiers were unsatisfactory in classifying built-up areas, whereas object-based classifiers had better results. Image segmentation, the first step in an object-based classification, can considerably influence the results of the classification task. It is therefore essential that suitable image segments be generated before the segments are classified. The proposed The proposed methodology involves the use of cadastral data in the image segmentation process and texture measures in the classification of built-up areas within an object-based process. The method can be applied to diverse scenes across South Africa to find built-up areas. This is a generalised approach and can assist the CD: NGI in the process of updating their topographic database by reducing the time that operators spend on identifying and manually digitizing built-up areas.
Open Access
Development of an integrated information system for archaeological heritage documentation
(2000) Rivett, Ulrike Karin; Rüther, Heinz
The traditional methods for the documentation of archaeological heritage sites are challenged today by developments in geomatics, information technology and the computer industry. Non-contact spatial measurement methods, as well as new spatial information systems technologies and computer visualisation tools have introduced a new age for conservation and site research. This thesis uses the instance of the documentation of the 3.6 million-year-old hominid footprint trackway in Laetoli, Tanzania, to address the need for an adequate scientific method to acquire, manage and visualise spatial data for the re-creation of archaeological heritage sites in a three-dimensional virtual world. The Laetoli site presents the first physical evidence of human bipedalism. Its consequent significance to human evolutionary science justifies the need for highly detailed and accurate documentation of its characteristics. The thesis explores digital photogrammetric techniques as data acquisition tools for this kind of close range archaeological environment. Specifically, it examines issues such as non-contact measurements, cost-effectiveness, and functionality in harsh conditions.The data collected at Laetoli had to be organised, managed and presented to allow future research on the footprints and to allow the general public to "visit" the site. This thesis shows how a spatial information system is used to manage spatial and meta data, while an integrated visualisation tool offers a virtual 3D reconstruction ofthe heritage site.
Open Access
Digital photogrammetry for visualisation in architecture and archaeology
(2000) Hull, Simon Antony; Rüther, Heinz
The task of recording our physical heritage is of significant importance: our past cannot be divorced from the present and it plays an integral part in the shaping of our future. This applies not only to structures that are hundreds of years old, but relatively more recent architectural structures also require adequate documentation if they are to be preserved for future generations. In recording such structures, the traditional 2D methods are proving inadequate. It will be beneficial to conservationists, archaeologists, researchers, historians and students alike if accurate and extensive digital 3D models of archaeological structures can be generated. This thesis investigates a method of creating such models, using digital photogrammetry. Three different types of model were generated: 1. the simple CAD (Computer Aided Design) model; 2. an amalgamation of 3D line drawings; and 3. an accurate surface model of the building using DSMs (Digital Surface Models) and orthophotos.
Open Access
Effectiveness measures for geographical information systems (GIS)
(1998) Tanner, Christopher Barrat; Barry, Michael B
Geographical Information Systems (GIS) often do not meet the expectations of users and management, raising questions and doubts as to their overall success and effectiveness. To date the majority of GIS research has focused on technical issues, and management research has approached GIS effectiveness from a purely cost benefit perspective. This study adopts a holistic, multi-perspective approach to the issue of GIS effectiveness, identifying measures of effectiveness related to the fields of Information Systems (IS), Management Information Systems (MIS) and GIS. It applies these measures using the case study methodology in a small South African local authority, the Ceres Municipality.
Open Access
Enhancing point cloud processing using audio cues
(2014) Ntsoko, Thabo; Sithole, George
Today many airborne and terrestrial acquisitions capture point clouds of scenes or objects to be modelled. But before modelling can be done point clouds need to be taken through processing steps such as registration, cleaning, simpli_cation, etc. These point clouds are usually manually processed before being processed automatically. Manual processing of point clouds depends on the visual interaction the user has with the point cloud provided by the visual cues. This research investigated enhancing the level of interaction the user has with the point cloud when processing it. The proposed method augments audio in point clouds to enhance its processing where visual cues are limited. This investigated _nding objects/points of interest in the point cloud while processing it by estimating the position (azimuth and elevation) and depth of audio objects associated with these point cloud objects. The occupancy of space of audio objects was also investigated to determine the unseen events around objects of interest in the point cloud. For example, in a scan registration problem, audio could be augmented to a misaligned scan. As this scan is manually rotated and translated into alignment, various audio cues can be used to inform the user of the state of this alignment. An outlier separated from a surface in a point cloud could be identi_ed and removed by augmenting audio to a volumetric brush that does the point cloud cleaning. Associating audio cues of the audio object with the depth of the outlier to the surface could help the user identify this outlier. Similar implementation could be adopted in point cloud simpli_cation tasks. Various audio cues exist which allow a listener to discern particular information about a sound source. This is done by the human auditory system, using cues such as intensity, pitch, reverberation and HRTFs to discern this information. However, limitations exist in retrieving this information. Literature supports the use of the auditory interface in applications commonly built for the visual interface. The addition of the auditory interface is seen as a way of increasing the interaction users have with applications and therefore improving the experience. An auditory interface was built to help undertake this research. The test subject was immersed in the auditory environment by wearing headphones. This meant that the subject and the virtual listener were merged, allowing the subject to receive emitted audio. The perception of the audio was with respect to the virtual listener.
Open Access
Establishment of Accuracy Testing Facilities for Terrestrial Laser Scanners
(2018) Davison, Wayne; Smit, Julian Lloyd
Measurement instruments that are required for high precision and reliable work need to have regular checks to ensure they are always performing at the required level of accuracy. A Terrestrial Laser Scanner is one such instrument and with the vast amount of information that this machine is able to capture, it is especially important to run regular accuracy checks. This research is building on the work that has been done by previous researchers on the assessment of instrument accuracy and the establishment of facilities specialized for this assessment. Theoretical principles are investigated in the form of Least Squares Adjustments, similarities to panorama photography and photogrammetric accuracy. Terrestrial Laser Scanners are reviewed with respect to their scanning principles and data acquisition. The methodology incorporated in this research encompasses the positioning of targets, their survey to establish high accuracy coordinates through various methods of adjustment and thereafter the scanning of those targets. Comparisons were done using derived angles and distances between the targets to discover the point accuracy of the Laser Scanner. This was done for two facilities; a short range facility (1 to 15 meters) and a medium range facility (1 to 75 meters). The medium range facility also included a range testing baseline for distance accuracy assessments. The outcomes from the comparisons between the surveyed control data and the laser scanner observed data indicated that the laser scanner is performing below the accuracy of the surveyed data. The laser scanner was further compared against the manufacturer quoted performance specifications and revealed the laser scanner to be performing below the quoted values. The laser scanner in question showed stronger results in the horizontal measurements over the vertical measurements. All results suggested the laser scanner was delivering weak results in the vertical observations due to a mis-alignment of individual scan halves. This research was able to establish two accuracy assessment facilities specialized for Terrestrial Laser Scanners under these same conditions. Both facilities were used in conjunction, to analyze the Z+F Imager 5010C laser scanner and determine the point accuracy in terms of the observed angles and distances from this machine. The results are also able to identify errors in the performance of the laser scanner and whether or not it is performing within the manufacturer specifications by noticing any large values such as in the case of the vertical observations for this instrument.
Open Access
The estimation of precipitable water vapour from GPS measurements in South Africa
(2005) Wonnacott, R T; Merry, Charles
The propagation of the Global Positioning System (GPS) signal from the satellite to the receiver is affected by, among other factors, the atmosphere through which it passes and, whereas the affects of the ionosphere can be eliminated by the differencing of two transmitted frequencies, the affects of the troposphere remain one of the major sources of noise in traditional geodetic and positioning applications of GPS. This noise can, however, be turned into a signal for the meteorologist and, by applying suitable constraints and processing strategies, it is possible to estimate the amount of precipitable water vapour (PWV) in the atmosphere. The application of the GPS data for the estimation of PWV in the atmosphere is not a new concept and has been described in numerous publications and reports since the early 1990's (Bevis et al., 1992, Rocken et al., 1993). This project is, however, an attempt to test the technique using the South African network of permanent GPS base stations. This thesis sets out to answer four fundamental questions: i. In theory, can GPS observations be used to estimate the amount of precipitable water vapour (PWV) in the atmosphere? ii. What permanent GPS networks are being used in other countries around the world for similar applications and how successful are these applications? iii. Can data derived from the South African network of permanent GPS base stations, TrigNet, be used to estimate PWV with sufficient accuracy to be able to supplement the radiosonde upper air measurements of the South African Weather Service (SAWS)? iv. Is the estimation of PWV as derived from the GPS observations a true reflection of reality using the radiosonde ascent measurements and numerical weather model (NWM) data as a method of independent verification? The primary data sets used to estimate atmospheric PWV at hourly intervals for March 2004 were; i. GPS data derived from the South African network of permanent GPS base stations provided by the Chief Directorate of Surveys and Mapping (CDSM); and ii. Surface meteorological measurements supplied by the South African Weather Service (SAWS). The two independent data sets used to verify and test the technique were; i. Upper air measurements derived from radiosonde ascents provided by the SAWS. These measurements were used to compute Integrated Water Vapour (IWV) and then converted to PWV; and ii. PWV estimates derived from a Numerical Weather Model provided by the Department of Environmental and Geographical Sciences of UCT. By the comparing the estimates of PWV from the three techniques, viz. GPS, radiosonde and NWM, it was found that GPS will meet the accuracy requirements of the meteorologist and could be used to supplement radiosonde measurements for use in numerical weather models.
Open Access
Field computers for spatially referenced social surveys
(2001) Barodien, Glynnis Erica; Barry, Michael
This study explores the use of a palm computer, linked to a hand held global positioning system receiver, by members of an informal settlement and a rural community to collect socio-economic (SE) data. The theoretical foundation is taken from such disciplines as Semiotics, Human Computer Interaction (HCI) and Survey Research Methods. This theory was used to develop a methodology, which enabled the researcher to investigate whether it is feasible to use icons to represent SE variables, whether HCI theory is useful for assessing the field observations of the volunteers using the palm computer, and whether the data collected is useful in terms of informal settlements and Communal Property Associations (CPA's). The research approach involved developing a set of icons, which were then pretested using feedback from volunteers in Mitchell’s Plain (Cape Town) before doing field-testing in Algeria and Imizamo Yethu. Next, two field studies were conducted. In Algeria and Imizamo Yethu, the volunteers were asked to identify a set of SE icons, they were taught how to use the palm computer and the CyberTracker software, and each volunteer was asked to conduct a mini-survey. The volunteer responses to the SE icons were analysed using semiotic criteria to determine how well they identified the icons. Next, the field observations were assessed with usability criteria from HCI. Finally, the two data sets were evaluated to determine its usefulness. The recommendations of this research are that if a set of SE icons is to be developed, the researcher suggests that symbols, which are well known by the community be used. That these symbols be tested in a 32x32 pixel format to determine if there is enough detail for recognition. Also, avoid detail in a picture that could cause confusion. Also, detailed investigations into the effect of culture, gender and background, as well as human perception is needed with the focus on communities. The main motivation for this is that informal settlements are a mix between rural, urban, educated and not, and also having different cultures. Next, it is further recommended that tests in homogeneous communities also be done to determine whether they do have the same mental concept. Further field studies are required to sort out various technical problems and to test a larger set of icons. Finally, other applications for this system should be investigated, e.g. land allocation distribution.
Open Access
Flood modelling using data available on the Internet
(2011) Pretorius, M J; Smit, Julian
The aim of this study was to determine if sufficient data at no charge is available on the Internet to use as input to a free and open source hydrological model for use in a flood monitoring system. As such, the monitoring system would be SensorWeb enabled. The study area is the C83A quaternary catchment (746 km2) in the Northern Free State, part of the Vaal primary catchment in South Africa.