ete ($5 
pet — Ma 
4 
  
  
  
  
  
the previous contour line map (Figure 1). In this 
image, there are steep slopes along the contour 
lines. And other area become flat. In this method, 
definition of weight and window size is difficult. 
And in case of complicated contour line, a detail 
can't be represented. 
Therefore, more reliable method of the 
interpolation should be developed when rough 
contour line map is used. 
3. DEVELOPED INTERPOLATION 
We attempted to develop a new method using 
buffering which is one of GIS techniques. In this 
paper, this method is called "buffering method”. 
The buffering method is not calculate pixel by 
pixel, which is based on an intermediate contour 
line derivation. The intermediate contour line can 
be drawn by using buffering image. Buffering can 
extracts distance from any points, vectors or 
polygons. In raster type data, distance is given to 
each pixel as an attribute. Figure 4 shows 
illustration of intermediate contour line 
derivation. If we have 100m and 200m contour line 
in the image, the distance from each contour line 
can be set to whole pixels. For example, gray level 
shows distance from contour line. Therefore, the 
intermediate contour line is located on same 
distance from each contour line. Same distance 
points from each contour line compose intermediate 
contour line. On the other hand, we have another 
easy process to draw intermediate contour line. It is 
based on making fat contour line. Every contour line 
is made fat by one pixel at a same time until whole 
pixels are fill with contour line value. That is one 
application of Morphology (Serra, 1988). Then, 
boundaries of the contour line becomes 
intermediate contour line. After that, newer 
intermediate contour line can be drawn from 
previous intermediate contour line and original 
contour line. By iteration of this process, 
intermediate contour line should be drawn until 
whole pixels are fill with contour line. 
The intermediate contour line derivation 
could be applied in case of enclosed area with 
different contour line. By the way, other area 
which enclosed with same contour line must be 
calculated by different method. Such area is 
corresponded to valley or ridge area. A buffering 
can also apply in such area. Figure 5 shows 
illustration of buffering result in enclosed area 
with 200m contour line. The buffering result can be 
seen like contour line itself. Therefore, same 
elevation can be given to same buffering pixels. In 
  
  
  
  
  
Figure 4 Illustration of intermediate contour line 
generation in case of enclosed area 
with different contour line 
  
  
  
  
  
Figure 5 Illustration of buffering results in case o 
enclosed area with same contour line 
  
Figure 6 Shaded DEM from Buffering method 
849 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996