The repair cost for deteriorating sewers had led to the growing use of closed circuit television surveys to assess their condition. A more objective assessment of these sewers was required since information from these surveys was being used to allocate scarce resources. The useful information produced by TV surveys was increased by the adoption of the principle of an optical section. A special light-head was placed in front of a TV camera such that a ring of light was projected onto the pipe, perpendicular to the pipe's axis. The camera viewed this ring of light and any deformation in the pipe was reproduced by the light-ring. Using a microcomputer as the controller, a framestore digitised the video signal from the survey camera, and the picture information was downloaded into the computer memory. The initial research period was spent developing a reliable algorithm which could accurately identify the light-ring with the minimum number of errors. This was achieved by examining the digital map of the picture for specified gradients of light which generally only occurred at the light-ring. A mathematical representation of the profile coordinates was created using Fourier Desciptors. This model allowed diameter measurements to be extracted to an accuracy of 0.2% when using a solid state camera, and each profile could be stored in 100 bytes. This system was proved in field trials. It was shown by Cluster Analysis that the deformed shape of a pipe could be classified by the use of its Fourier Desciptors. It is expected that when a large enough database has been gathered the structural stability of a sewer may be automatically assessed from this mathematical representation of its profile.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:637264 |
| Date | January 1986 |
| Creators | Henry, R. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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