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.

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In Australia, in recent years there has been increasing demand for more streamlined lodgement of cadastral plans and for their later dissemination. There are a number of approaches to meeting this demand, one of which is developed in detail in this dissertation. The current status of digital lodgement and Digital Cadastral Databases (DCDB) throughout Australia and New Zealand is reviewed. Each of the states and territories in Australia and also New Zealand are examined, looking at the process involved in the lodgement of survey plans and the state of the DCDB in each jurisdiction. From this examination the key issues in digital lodgement and dissemination are extracted and a needs analysis for an Australia-wide generic system is carried out. This needs analysis is directed at technological change allied with sound cadastral principles. Extensible Markup Language (XML) is considered for the storage and transport of all the required data and to facilitate the dissemination of information over the Internet. The benefits of using XML are comprehensive, leading to its selection and the use of related technologies LandXML, Extensible Structured Query Language (XSQL) and Extensible Stylesheet Language (XSL). Vector graphics are introduced as the means to display plans and maps on the Internet. A number of vector standards and Web mapping solutions are compared to determine the most suitable for this project. A new standard developed by the World Wide Web Consortium (W3C), Scalable Vector Graphics (SVG), is chosen. A prototype Web interface and the underlying database and Web server were developed using Oracle as the database and Apache as the Web server. Each aspect of the development is described, starting with the installation and configuration of the database, the Web server and the XSQL servlet. Testing was undertaken using LandXML cadastral data and displaying plans using SVG. Both Internet Explorer and Mozilla were trialled as the Web browser, with Mozilla being chosen because of incompatibilities between Internet Explorer, LandXML and SVG. An operational pilot was created. At this stage it requires manual intervention to centre and maximise a plan in the display area. The result indicates that an automated system is feasible and this dissertation provides a basis for further development by Australian land administration organisations.