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LINEAMENT ANALYSIS

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Letís discuss the main, fundamental recommendations that help to use LESSA properly. How to analyze LESSA results - extreme regions, high gradient zones, elongation lines, long lineaments - is described in the South-West Africa image analysis example. Particular methods for certain investigations one can find in the automatic lineament analysis applications

Information provided by LESSA, and first of all rose-diagrams and fields, is objective image (texture) description. Only a specialist can decide if the image reflects those structures that he is looking for or not. But to obtain suitable characteristics of the area itís necessary to choose proper input data.

First of all the image must be clean, not covered with clouds, artificial objects, noise etc. Notice that accurate processing of Ukrainian and Hungarian images where land is covered with agricultural fields gave appropriate structural information.

The second important decision that user must make is the input image scale (pixel size) choosing. We must notice that this choice is quite different from the traditional scale choice for the visual image analysis. We can be guided by the size of the basic structures, those that "born" stripes - the basis of the LESSA processing. According to their size one can choose the image scale (digitization step or pixel size). Itís necessary to take into account that different scale can give us not the same image description with more details or less, but we can get description of the OTHER image, that is formed by the structures of the other size, and can be rather different. Itís obvious that if too coarse resolution is used we can miss the basic structures and if the resolution is too high we can detect small details of those structures with different orientation.

Rose-diagrams sliding window size determines size of the structures that could be detected by the stripes statistical analysis. We must notice that the window canít be of arbitrary size. Statistical reasons give the working size range. The optimal size is about 64 pixels. In the much larger windows rose-diagrams appear to be almost round, without essential distinctions. In the smaller window there are too few stripes, so the roses shape is coarse and its descriptors are not stable.

Long lineaments detection also needs such accurate resolution choice - if the resolution is too high lineaments can turn out to be meandering, not straight and LESSA will miss them.

There is also specific scale choice for schemes and DTM.

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