Data capture of geometric data for local authorities' geographic information systems

Master Thesis


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University of Cape Town

This thesis describes research and development work which led to algorithms, procedures and computer programs which facilitate the cost effective and accurate capture of geometric data. The geometric data for a Geographical Information System (GIS) at a local authority or municipality consist of a number of different data sets. These include inter alia: the cadastral information, zoning information, servitudes, building lines, the outlines of improvements and the reticulation networks and the house connection points of the engineering services. The initial capture of the geometric data appears to be deceptively simple and is often not given the required consideration. The initial data capture phase of GIS projects is usually a difficult and time consuming process. This is even more so in the case of GIS for local authorities. The reason for this difficulty is the large volume of data coupled with the high accuracies required for the cadastral base map and the engineering services. Input facilities of most commercial GIS software packages generally do not provide the most efficient means of data capture. This problem warrants the development of techniques and procedures specific to local authority GIS applications which ensure that data capture can be done effectively and efficiently. The major benefit of these procedures is that they can be implemented on personal computers with low random access memory capacity. This eliminates the need for investment in costly equipment at the initial stage of data capture in the development of a GIS. It allows the capture of data on low cost technology and the postponement of the purchase of an expensive system or workstation until the data capture phase has been completed. The lowest personnel skills required are copy typing in contrast to the traditional methods of using CAD operators who command higher salaries and require more expensive training. The system developed by the author is more productive, both in quality and volume of work produced, than the CAD approach. It also permits the delay of purchase and training on expensive GIS software and hardware, which may be obsolete by the time the graphic database is established.

Bibliography: leaves 64-65.