Browsing by Author "Hendriks, Lukas Anton"
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- ItemDie geskiedenis van die Nederduitse Gereformeerde Gemeente van Graaff-Reinet, 1792-1822(Stellenbosch : Stellenbosch University, 1987-12) Hendriks, Lukas Anton; Venter, C.; Stellenbosch University. Faculty of Arts and Social Sciences. Department of History.No abstract available
- ItemImage processing techniques for sector scan sonar(Stellenbosch : University of Stellenbosch, 2009-12) Hendriks, Lukas Anton; Treurnicht, J.; University of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.ENGLISH ABSTRACT: Sonars are used extensively for underwater sensing and recent advances in forward-looking imaging sonar have made this type of sonar an appropriate choice for use on Autonomous Underwater Vehicles. The images received from these sonar do however, tend to be noisy and when used in shallow water contain strong bottom reflections that obscure returns from actual targets. The focus of this work was the investigation and development of post-processing techniques to enable the successful use of the sonar images for automated navigation. The use of standard image processing techniques for noise reduction and background estimation, were evaluated on sonar images with varying amounts of noise, as well as on a set of images taken from an AUV in a harbour. The use of multiple background removal and noise reduction techniques on a single image was also investigated. To this end a performance measure was developed, based on the dynamic range found in the image and the uniformity of returned targets. This provided a means to quantitatively compare sets of post-processing techniques and identify the “optimal” processing. The resultant images showed great improvement in the visibility of target areas and the proposed techniques can significantly improve the chances of correct target extraction.