5.1 Rigid Transfer of Seed Points 
In the first stereo pair the seed points for matching have to be 
measured manually. Then the matching procedure is executed. 
This leads to a large number of conjugate points. Because of the 
small wave motion the conjugate points of this pair (called pair 
[i] in the following) can be utilized as seed points for the 
following time step [i+1] (see also Figure 3). In order to reduce 
the matching effort only a pre-specified amount of seed points is 
used. Well distributed points with a high correlation coefficient 
are selected. Then, the matching of the stereo images [i+1] is 
carried out, the results can then be used in the same way for the 
stereo images [i+2] and so on. 
  
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Figure 3. Principle of transfer of seed points 
The analysis of image sequences using the rigid transfer of seed 
points does not take the movement of the sea surface into 
consideration. Thus a number of seed points for matching the 
pair [i*n; n21] does not lead to successful results. However this 
loss is compensated by the large amount of available seed 
points. 
5.2 Motion Analysis 
It is also feasible regarding image sequence analysis to take the 
movement of the sea surface into account, for example based on 
a vector field modelling motion from one time epoch to the next 
(Jähne, 1991). The vector field provides information about the 
direction and velocity of the movement. 
5.2.1 Motion Models: Assuming a successful matching 
between an image [i] and its successor [i+1] of one image 
sequence taken by one camera, a large set of conjugate points in 
both images is available. Since these images represent one view 
at consecutive time steps, the position difference of any of the 
matched conjugate points in image space can be interpreted as a 
displacement or movement vector of that point. All 
displacement vectors of all conjugate points form the vector 
field, which represents a model of measured pixel movements. 
Since the time interval between image [i] and [i+1] is not only 
the same as between image [i+1] and [i+2] but also very small, 
the assumption of a linear approximation of the water mass 
movement during the period [i] to [i+2] is assumed to be valid 
for a significant number of points. Therefore the position of a 
point at time [i+2] can be predicted by extrapolation of the 
movement measured between [i] and [i+1] (see Figure 4). This 
results in a large variety of potentially corresponding points 
between the images [i+1] and [i*2]. Out of them a new set of 
seed points is chosen. Then, the matching [i+1] and [i42] is 
performed. This yield a new set of corresponding points in [i+1] 
and [1*2]. 
À pre [i+1] := 
j predicted * pos [i] * mov [i-1,i] 
{positions [i+1] 
  
   
  
     
  
| seedpoints | Vet 
mov [i] = 
  
pos [i*1] - pos [i] d 
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motion model [i] 
| [fir] | 
  
    
   
  
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i | predicted! — pos [i*1] * mov [ii 1] 
| (positions [ir2T) 
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[i+1] ~ [i+2] 
   
  
mov [i+1] := 
pos [i+2] - pos [i+1] 
    
  
  
  
i 
FE 
  
  
motion model [i1] | | 
   
: E pre [#3] := | 
Nt I | predicted] POs [i+2] + mov [i+1,i+2] 
à . : | | posit 3r | 
Gr magelix2l™- 1 i 
Figure 4. Principle of motion models 
  
  
  
  
It is possible to match any image [i+n] with its successor 
[i+n+1] as long as the matching with the predecessor [i+n-1] 
was successful as well. Combining this knowledge with the fact 
that the very first matching step [0] to [1] of this image 
sequence can be done with manually measured seed points, it 
becomes obvious that all images of this sequence can be linked 
together by matching. Therefore a set of conjugate points and 
motion models can be derived for that sequence. 
5.2.2 Stereo Models: If a matching between a stereo image 
pair of time [i] is carried out, a set of conjugate points is the 
result. There exists no functional context between this stereo 
point set and the sets of conjugate points of the temporal 
matching within the left and right image sequence, but both sets 
refer to the same image space. 
After every motion model calculation a connection between the 
corresponding stereo images must be established. One 
opportunity to solve this problem is provided by using the 
motion model [i, i+1] for a stereo sequence of two images [i] 
and [i+1] and the subsequent stereo matching. In both images of 
the stereo pair [i] seed points are available from earlier 
computations. For the calculation of the vector field of the 
motion model in the left and right image sequence the same 
seed points have to be determined in the image [left, i+1] and 
[right, i+1]. The matching procedures for the stereo pair [i] and 
the motion models [left i, i+1] and [right i, i+1] are carried out. 
Then, the conjugated points of the stereo pair [i] are transferred 
by the use of the motion models into the images [i+1]. A 
matching of the image sequence [i+1] is carried out. From the 
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