Changes between Version 139 and Version 140 of UvmatHelp


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Timestamp:
Jan 14, 2015, 2:28:52 PM (6 years ago)
Author:
vaillant1p
Comment:

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  • UvmatHelp

    v139 v140  
    822822
    823823=== 11.3 FIX ===
    824 The FIX operation is used after civ to remove false vectors, using different criteria: -''' {warning flags:} ''' these are flags (vec_F) indicating problems with the image correlation process: -*vec_F(i)=0 or 1 : default , the processing is fine
    825 -*vec_F(i)=-2: the maximum of the correlation function is close to the border of the search box (at a distance of two pixels or less), so that its maximum cannot be reliably obtained: the search domain is too small
    826 -*vec_F(i)=2: (only in civ1) we keep the less accurate Hart result (resulting from combining correlation functions  from neighborhing points) and  vec_C(i)=-1 is chosen by convention. Reference: Hart D. P. (2000) 'PIV error correction',{ Exp. Fluids} '''29''', 13-22.
    827 -*vec_F(i)=3: the optimisation of the correlation function is unstable  or  local Intensity rms of the image =0
    828 -*vec_F(i)=4:only in civ2: the difference between the estimator and the result is more than 1 pixel. The two criteria, vec_F(i)=-2, and 3, should be selected (default options). The criterium vec_F=2 (Hart) should not be selected, while vec_F=4 (for civ2) could be selected only for excellent data (otherwise it may be too strict).   -''' {Threshold on the image correlation}  ''' (vec_C) can be introduced by the edit box [thresh_vecC] (value between 0 and 1). It removes vectors with poor correlation.  -''' {Threshold on the velocity modulus } ''' (expressed in pixels): it can remove either too small values  (menu '''[inf_sup1]''' set to '<'), or excessive values (menu '''[inf_sup1]''' set to '>'). Erratic zero velocity vectors, produced by a fixed image background, can be eliminated by this criterium. These criteria can be as well applied to the difference with a reference field, defined by a file series (edit box '''[ref_fix1]''') and a field inside the file (menu '''[field_ref1]'''). -''' {Mask fix:} '''  It has the same effect as the one used in civ1, but the removed vectors are kept in memory, labelled as false. -''' {Manual fix:} ''' Interactive fixing with the mouse is also possible, see [section 4.2->#4.2].
    829 
    830 -''' {Code for FixFlag:} ''' -*FixFlag(i)=0 :default, everything is fine -*FixFlag(i)=1. : value 1 for the second digit: vector removed by criteria on vec_F or/and low correlation value -*FixFlag(i)=1..: value 1 for the third digit: vector selected by a criterium of difference with another field, for instance filter, or a field with differnt time interval. -*FixFlag(i)=...1, 2, 3  different criteria for elimination set by the program Fix of CIVx (not yet documented).
     824The FIX operation is used after civ to remove false vectors, using different criteria: -''' {warning flags:} ''' these are flags (vec_F) indicating problems with the image correlation process: *vec_F(i)=0 or 1 : default , the processing is fine
     825*vec_F(i)=-2: the maximum of the correlation function is close to the border of the search box (at a distance of two pixels or less), so that its maximum cannot be reliably obtained: the search domain is too small
     826*vec_F(i)=2: (only in civ1) we keep the less accurate Hart result (resulting from combining correlation functions  from neighborhing points) and  vec_C(i)=-1 is chosen by convention. Reference: Hart D. P. (2000) 'PIV error correction',{ Exp. Fluids} '''29''', 13-22.
     827*vec_F(i)=3: the optimisation of the correlation function is unstable  or  local Intensity rms of the image =0
     828*vec_F(i)=4:only in civ2: the difference between the estimator and the result is more than 1 pixel. The two criteria, vec_F(i)=-2, and 3, should be selected (default options). The criterium vec_F=2 (Hart) should not be selected, while vec_F=4 (for civ2) could be selected only for excellent data (otherwise it may be too strict).   -''' {Threshold on the image correlation}  ''' (vec_C) can be introduced by the edit box [thresh_vecC] (value between 0 and 1). It removes vectors with poor correlation.  -''' {Threshold on the velocity modulus } ''' (expressed in pixels): it can remove either too small values  (menu '''[inf_sup1]''' set to '<'), or excessive values (menu '''[inf_sup1]''' set to '>'). Erratic zero velocity vectors, produced by a fixed image background, can be eliminated by this criterium. These criteria can be as well applied to the difference with a reference field, defined by a file series (edit box '''[ref_fix1]''') and a field inside the file (menu '''[field_ref1]'''). -''' {Mask fix:} '''  It has the same effect as the one used in civ1, but the removed vectors are kept in memory, labelled as false. -''' {Manual fix:} ''' Interactive fixing with the mouse is also possible, see [section 4.2->#4.2].
     829
     830''' {Code for FixFlag:} '''
     831*FixFlag(i)=0 :default, everything is fine
     832*FixFlag(i)=1. : value 1 for the second digit: vector removed by criteria on vec_F or/and low correlation value
     833*FixFlag(i)=1..: value 1 for the third digit: vector selected by a criterium of difference with another field, for instance filter, or a field with differnt time interval.
     834*FixFlag(i)=...1, 2, 3  different criteria for elimination set by the program Fix of CIVx (not yet documented).
    831835
    832836=== 11.4 PATCH ===