Patent ID: 11900619
Assignee: nan
Field: Audio-visual technology (Electrical engineering)
Classification: CPC G  H | IPC G  H

Claim 4:
5. The method for intelligently measuring vehicle trajectory based on a binocular stereo vision system according to claim 1, wherein the feature-based matching algorithm is a SURF feature extracting and matching algorithm, the local features of the video frames are described by the SURF descriptors, wherein the homography matrix describes the relationship between two images of the same object taken in the different views, the relationship of the two images is perspective transformation, then the homography matrix H is:, H
    =
    
     [
     
      
       
        
         h
         
          1
          ⁢
          1
         
        
       
       
        
         h
         
          1
          ⁢
          2
         
        
       
       
        
         h
         
          1
          ⁢
          3
         
        
       
      
      
       
        
         h
         
          2
          ⁢
          1
         
        
       
       
        
         h
         
          2
          ⁢
          2
         
        
       
       
        
         h
         
          2
          ⁢
          3
         
        
       
      
      
       
        
         h
         31
        
       
       
        
         h
         
          3
          ⁢
          2
         
        
       
       
        1
       
      
     
     ]
    
   
   ;
  
  ⁢
  

  then
  ⁢
  

  
   
    
     [
     
      
       
        
         x
         ′
        
       
      
      
       
        
         y
         ′
        
       
      
      
       
        1
       
      
     
     ]
    
    =
    
     
      [
      
       
        
         
          h
          
           1
           ⁢
           1
          
         
        
        
         
          h
          
           1
           ⁢
           2
          
         
        
        
         
          h
          
           1
           ⁢
           3
          
         
        
       
       
        
         
          h
          
           2
           ⁢
           1
          
         
        
        
         
          h
          
           2
           ⁢
           2
          
         
        
        
         
          h
          
           2
           ⁢
           3
          
         
        
       
       
        
         
          h
          31
         
        
        
         
          h
          
           3
           ⁢
           2
          
         
        
        
         1
        
       
      
      ]
     
     [
     
      
       
        x
       
      
      
       
        y
       
      
      
       
        1
       
      
     
     ]
    
   
   ,
  
 

wherein x′, y′, 1 and x, y, 1 represent the coordinates of the two corresponding points before and after the perspective transformation respectively, and h11-32 are transformation parameters to be calculated to calculate the eight transformation parameters h11-32 in the homography matrix H, at least four pairs of matching points are needed, the process is as follows:, [
     
      
       
        
         
          x
          1
         
         ,
         
          y
          1
         
         ,
         1
         ,
         0
         ,
         0
         ,
         0
         ,
         
          
           -
           
            x
            1
            ′
           
          
          ⁢
          
           x
           1
          
         
         ,
         
          
           -
           
            x
            1
            ′
           
          
          ⁢
          
           y
           1
          
         
        
       
      
      
       
        
         0
         ,
         0
         ,
         0
         ,
         
          x
          1
         
         ,
         
          y
          1
         
         ,
         1
         ,
         
          
           -
           
            y
            1
            ′
           
          
          ⁢
          
           x
           1
          
         
         ,
         
          
           -
           
            y
            1
            ′
           
          
          ⁢
          
           y
           1
          
         
        
       
      
      
       
        
         
          x
          2
         
         ,
         
          y
          2
         
         ,
         1
         ,
         0
         ,
         0
         ,
         0
         ,
         
          
           -
           
            x
            2
            ′
           
          
          ⁢
          
           x
           2
          
         
         ,
         
          
           -
           
            x
            2
            ′
           
          
          ⁢
          
           y
           2
          
         
        
       
      
      
       
        
         0
         ,
         0
         ,
         0
         ,
         
          x
          2
         
         ,
         
          y
          2
         
         ,
         1
         ,
         
          
           -
           
            y
            2
            ′
           
          
          ⁢
          
           x
           2
          
         
         ,
         
          
           -
           
            y
            2
            ′
           
          
          ⁢
          
           y
           2
          
         
        
       
      
      
       
        
         
          x
          3
         
         ,
         
          y
          3
         
         ,
         1
         ,
         0
         ,
         0
         ,
         0
         ,
         
          
           -
           
            x
            3
            ′
           
          
          ⁢
          
           x
           3
          
         
         ,
         
          
           -
           
            x
            3
            ′
           
          
          ⁢
          
           y
           3
          
         
        
       
      
      
       
        
         0
         ,
         0
         ,
         0
         ,
         
          x
          3
         
         ,
         
          y
          3
         
         ,
         1
         ,
         
          
           -
           
            y
            3
            ′
           
          
          ⁢
          
           x
           3
          
         
         ,
         
          
           -
           
            y
            3
            ′
           
          
          ⁢
          
           y
           3
          
         
        
       
      
      
       
        
         
          x
          4
         
         ,
         
          y
          4
         
         ,
         1
         ,
         0
         ,
         0
         ,
         0
         ,
         
          
           -
           
            x
            4
            ′
           
          
          ⁢
          
           x
           4
          
         
         ,
         
          
           -
           
            x
            4
            ′
           
          
          ⁢
          
           y
           4
          
         
        
       
      
      
       
        
         0
         ,
         0
         ,
         0
         ,
         
          x
          4
         
         ,
         
          y
          4
         
         ,
         1
         ,
         
          
           -
           
            y
            4
            ′
           
          
          ⁢
          
           x
           4
          
         
         ,
         
          
           -
           
            y
            4
            ′
           
          
          ⁢
          
           y
           4
          
         
        
       
      
     
     ]
    
    [
    
     
      
       
        h
        11
       
      
     
     
      
       
        h
        12
       
      
     
     
      
       
        h
        13
       
      
     
     
      
       
        h
        21
       
      
     
     
      
       
        h
        22
       
      
     
     
      
       
        h
        23
       
      
     
     
      
       
        h
        31
       
      
     
     
      
       
        h
        32
       
      
     
    
    ]
   
   =
   
    [
    
     
      
       
        x
        1
        ′
       
      
     
     
      
       
        y
        1
        ′
       
      
     
     
      
       
        x
        2
        ′
       
      
     
     
      
       
        y
        2
        ′
       
      
     
     
      
       
        x
        3
        ′
       
      
     
     
      
       
        y
        3
        ′
       
      
     
     
      
       
        x
        4
        ′
       
      
     
     
      
       
        y
        4
        ′
       
      
     
    
    ]
   
  
  ;
 

each time, four pairs of matching points are selected from all the matching points to calculate the homography matrix H; then the homography matrix with the maximum number of accurate matching points is selected as the most accurate homography matrix H to check the accuracy of the matrix H, the Euclidean distance between the corresponding matching points is calculated:, 
   
    
     [
     
      
       
        
         x
         
          i
          ⁢
          1
         
         ′
        
       
      
      
       
        
         y
         
          i
          ⁢
          1
         
         ′
        
       
      
      
       
        1
       
      
     
     ]
    
    -
    
     H
     [
     
      
       
        
         x
         
          i
          ⁢
          1
         
        
       
      
      
       
        
         y
         
          i
          ⁢
          1
         
        
       
      
      
       
        1
       
      
     
     ]
    
   
   
  
  ≤
  t
 

wherein xi1′, yi1′, 1 and xi1, yi1, 1 are the coordinates of the matching points before and after the perspective transformation, t is the Euclidean distance threshold, and i1=1,2,3,4 wherein the smaller the Euclidean distance, the higher the matching accuracy of the two corresponding matching points.