Changes between Version 9 and Version 10 of Tutorial/AdvancedParticleImagingVelocimetry2


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Timestamp:
Aug 27, 2013, 9:26:12 AM (8 years ago)
Author:
sommeria
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  • Tutorial/AdvancedParticleImagingVelocimetry2

    v9 v10  
    33
    44= calibration =
    5 mark corners
     5mark the four box corners with the mouse. We find ....
     6The corresponding physical coordinates are known to be (0,0),(58.8,0),(58.8,55.1),(0,55.1), with an origin (0,0) taken at the lower left. Introduce those in the table ![ListCoord]. This can be conveniently done by copy paste of the Matlab vector x=[0 58.8 58.8 0] in the upper line of the x column, and y=[0 0 55.1 55.1] in the y column (use carriage return to validate the input).
     7Then apply rescale. we observe that the figre is slightly rotated.
     8We then apply linear which allows for rotation. The precison is improved.
    69
    710= mask =
     11Open the original image with uvmat, selecting the transform option 'phys'.  withCreate a mask polygon by the menu bar command Projection object/mask_polygon. Set the option 'mask_outside' and introduce the coordinates of the four corners in Coord (like for geometry calib). Plot the polygon. Then create the corresponding mask by '''Tools/make mask'''.
    812
    913= sub_background =
     14We observe parasitic light rays on the images which correspond to fixed features, leading possibly to spurious velocity vectors equal to 0. To eliminate those we use sub_bacground.
     15Open the image with 'series' and select the program 'sub_background'. This function is not provided in the default menu, so you need to use the last menu option 'more...', and select the function in the sub-folder 'series/' of the package uvmat. This option is then preserved in the menu for later use.
     16Then run sub_background over the whole index range in i and j, using the default parameters. Answer Yes to the quaestion 'apply levels', which will conveniently rescale the image brightness after background removal.
    1017
    1118= first PIV =