Changes between Version 187 and Version 188 of UvmatHelp


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Timestamp:
Jan 28, 2015, 5:11:10 PM (6 years ago)
Author:
vaillant1p
Comment:

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  • UvmatHelp

    v187 v188  
    818818('''[num_!CorrBoxSize_1,_2,_3])''' set the size (in pixels) of the 'correlation box', the sliding window used to get image correlations. '''[num_!SearchBoxSize_1,_2,_3]''' set the size of the 'search box' in which image correlation is calculated, see figure.  This search box can be shifted with respect to the correlation box by parameters  ('''[num_!SearchBoxShift_1,_2,_3]'''). This is useful in the presence of a known mean flow. The default value '''[!SearchBoxSize]'''=(25,25) is generally good, use a larger size for images with few particles, use an elongated box , e.g. (11,41), to optimise the resolution in one direction (for instance in a boundary layer).
    819819
    820 A parameter '''[num_CorrSmooth]''' controls the smoothing of the image corelation curves used in civ, the default value 1 is generally used.
     820A parameter '''[num_CorrSmooth]''' controls the smoothing of the image corelation curves used in civ, the default value 1 is generally used. Its value is set according to [https://servforge.legi.grenoble-inp.fr/projects/soft-uvmat/attachment/wiki/UvmatHelp/Nobach%26Honkanen%282005%29.pdf Nobach & Honkanen work (2005)], '''[num_CorrSmooth]'''=1 means it will be a 2x3-point regression (3 points on the ''x'' axis and 3 points on the ''y'' axis) whereas '''[num_CorrSmooth]'''=2 means it will be a 9-point regression.
    821821
    822822The search parameters ('''[!SearchBoxSize]''', '''[!SearchBoxShift]''') can be estimated using the press button '''[search range]'''. First introduce the estimated minimum and maximum values of each velocity component u and v (expressed in pixel displacement). The result depends on the time interval of the image pair.
    823823
    824 [[Image(11-2 CV1.png)]]
     824  [[Image(11-2 CV1.png)]]
    825825
    826826The button '''[TEST]''' allows the user to witness the correlation as a live plot. It first opens the source image in a new figure '''view_field'''. By moving the mouse in the figure, the local correlation box and the corresponding search box are drawn in the image, and the 2D correlation result then appears in a new figure 'Figure1 Image Correlation' which automatically pops up. It is possible to freeze the current correlation plot by left mouse selection. The figure belows shows the correlation process and the '''[!SearchBox]''' and '''[!CorrBox]''' explained before.
    827827
    828 [[Image(civ1_test.jpg)]]
     828  [[Image(civ1_test.jpg)]]
    829829[[Image(Correlation for PIV.png)]]
    830830