Airborne electromagnetic methods were developed in the early 1950's, mostly by Canadian mining exploration companies as a means of economically and successfully searching large areas for conductive massive sulfide mineralisations. As new technologies developed they have become more and more sophisticated. They can detect conductors at depths in excess of 200 m and are routinely used for overburden mapping. The data is digitally recorded and processed. One of the most successful methods is the time domain airborne INPUT$ sp1$ system, for numerous mineral deposits were found by this system in the Canadian Shield. / Present interpretation techniques are based on the use of nomograms (i.e. families of pre-computed characteristic responses) and the method is easily amenable to digital processing as it is easy to program and economic to use. For high accuracy interpretation however it is necessary to develop quantitative interpretation techniques that can make full use of all the data available. Inverse theory has been used with great success in all branches of geophysics, but to date in mining exploration it has been used for the interpretation of airborne E.M. data using only the one layer earth model. Use of inverse theory for the plate model has been limited by the high cost of numerically solving the forward problem. / In this thesis we show how to use inverse theory to interpret time domain E.M. data with the rectangular thin plate model by introducing some economies. It is then possible to estimate parameter errors, the correlation matrix and to assess the validity of the model. This is extended to the joint inversion of magnetic and aeromagnetic data a case that often arises in mining problems. It is finally shown that under some assumptions the late time channels can be used to interpret time domain E.M. data in the presence of conductive overburden. ftn$ sp1$Registered trademark of Barringer Research Ltd.

No description available.

The Geodetic network of Lesotho as established by the Directorate of Overseas Surveys in the 1950's, has been known to have distortions of several meters in some areas. This network is still very much in use today. Several altcmpts were made to strengthen the DOS network. but these attempts were not used for a complete readjustment. The South African Control net, which completely surrounds Lesotho, has recently been readjusted so as to bring it into sympathy with the WGS reference system used by GPS. It has become urgent to similarly update the Lesotho control system, to enable economical use of GPS surveying methods. This thesis addresses the problems of updating the Lesotho control system and also of bringing existing data onto the updated systcm. This thesis first reviews the historical background of Lcsotho and that of its geodetic net work. Different sets of data were collected and common points in the compared sets selected for the analysis. The South African readjustment was chosen as the standard, because it is the most recent, derived with the support of the new zero-order South African control net. The data sets were fitted to the reference system using conformal transformations from first up to fourth order. These comparisons were used to detect outliers. They revealed systematic distortions in the older data. which could be largely eliminated in the fourth-order transformation. The opportunity to update control point co-ordinates also gave an opportunity to revisit the existing choice of using two map panels of the Gauss Conform projection. The distortions involved in using a single Gauss Conform panel and also the UTM projection were investigated. A companson or all the methods and the recommendations concludes the section. Software was developed for transforming existing survey data onto the recommended updated reference system. The height system used in Lesotho is also reviewed because it forms part of the control net. The focus is on heights in relation to gravity. because that bears on the relation of published orthometric heights. with GPS-derived ellipsoidal heights. This section is mostly a literature review, starting with the theory of heights and gravity, proceeding onto the applied corrections and then showing what relations have been found. / Thesis (M.Sc.Sur.)-University of Natal, Durban, 2001.

There is no abstract available for this thesis.

Problems with the identification and interpretation of rockshelter and cave sites were recognized in the archaeological literature from Indiana. Often, when these sites are identified in archaeological research and survey reports, realistic views of the potential cultural significance they may actually have is lacking. Based on data obtained from recent rockshelter surveys in southern Indiana, a method for evaluating the archaeological potential of rockshelter sites is presented. This methodology systematically accounts for geomorphological and geological factors as well as environmental considerations. Geographic information system (GIS) software is used to assist in the analysis and visualization of the variables associated with these rockshelters. While stressing the importance of these sites as potentially providing conditions for the preservation of cultural material, this method can also be used as a model for further studies on this topic. / Department of Anthropology

In a roofing project, acquiring the underlying as-built 3D geometry and visualizing the roof structure is needed in different phases of the project life-cycle. Architectural drawings, building information model (BIM) files, or aerial photogrammetry are used to estimate the roofing area in the bidding process. However, as a roof structure is never built to the exact drawing dimensions, as-built dimensions of boundaries of every roof plane have to be obtained several times during the course of its build. There are a number of surveying methods that can be used for this purpose: tape measuring, total station surveying, aerial photogrammetry, and laser scanning. However, obtaining measurements using these methods could be costly in terms of equipment, labor, and/or worker exposure to safety hazards. Aiming to address this limitation and provide roofing practitioners with an alternative roof surveying and visualization method that is simple to use, automated, inexpensive, and safe, a close-range videogrammetric roof 3D reconstruction framework is presented in this research. When using this method, a roofing contractor will simply collect stereo video streams of a target roof. The captured data is processed to generate a 3D wire-diagram for every roof plane. In this process, distinctive visual features of the scene (e.g., 2D points and lines) are first automatically detected and matched between video frames. Matched features and the camera calibration information are used to compute an initial estimation of the 3D structure. Then, a hybrid bundle adjustment algorithm is used to refine the result and acquire the geometry that has the maximum likelihood. Afterwards, different roof planes are found and a measurable 3D wire-diagram is generated for each plane.

A method is presented for the determination of interface topography of multi-layered crustal models from gravity or magnetic data. The technique is developed within the framework of discrete linear inverse theory and exploits the quasi-linearity of the problem to derive a simple cost-effective algorithm suitable for use on large gridded data sets. / Variation of auxiliary parameters allows a suite of acceptable models to be produced rapidly and appraised in the light of available geological and geophysical evidence. When independent knowledge concerning the behaviour of specified interfaces is available, the incorporation of such data in the form of linear equality constraints is outlined. / The proposed method is applied to Curie isotherm and Moho mapping in the Abitibi greenstone belt.

Thesis (MAppSc in Building Environment) --University of South Australia, 1991

Thesis (MAppSc in Building Environment) --University of South Australia, 1991

Thesis (MAppSc in Building Environment) --University of South Australia, 1991