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surface or in the form of a contour plot for example. Whilst 
all these data processing steps are currently only semi- 
able to provide sufficient processing power for complete 
automation and data processing during the experiment if 
automated, existing PC based computing facilities are 
required. 
y 
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triangulation 
   
N 
X 
X 
    
                             
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Figure 4. Soil surface computed after collapse. 
regular grid can be 
Delaunay 
interpolated on both the reference and comparison data 
       
identical 
   
NTS 
      
an 
             
> 
Figure 5. Difference between the original soil surface and that computed after collapse. 
AXP 
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set. A simple co-ordinate subtraction process can then be 
used to compute a new grid representing the difference 
A first step is to triangulate the data; this is carried out by 
between the two data sets. This grid may then be 
represented to the engineer as a computer generated 
the established method of 
(Preparata & Shamos, 1985). Once a triangle mesh has 
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(Unu) deg