The edit sequence is composed of the following steps: 
481 
Segmentation. The area of interest is specified and a bilevel 
image is created revealing the true resolution of the data (Figure 2b). 
This figure also presents the labeled connected components (1-3). 
Line Gap Edit. Component 3 is joined to component 2 by connecting 
the external contour maxima (pixel A) to the nearest external contour 
pixel of component 2 (pixel B). The width of the line which joins 
these two components is computed from the average width of component 
3. 
Overshoot Edit. After the operator indicates the area of interest 
by pointing^ the maxima and minima of the "holes" surrounding the area 
are specified by pixels C,D and E,F. A divide function logically 
separates and relabels connected components using the lines specified 
by C,D and E,F. Finally all relabeled pixels of the component 
representing the overshoot are removed by a delete function. The 
resulting image is shown in Figure 2c. 
Divide and Delete. To remove the extraneous line in Figure 2c, 
again the hole maxima pixels (A,D) and hole minima pixels (B,C) are 
computed. A logical divide and delete function removes the inter 
vening pixels resulting in display 2d. 
Output■ Finally, the image is returned to scale with all 
corrections made. 
SUMMARY 
This paper has defined some of the topological properties of raster 
data, presented an encoding scheme to represent the property of 
connectivity, examined the characteristics which can be derived from 
this encoding and illustrated a simple cartographic operation which 
can be enhanced by knowing these characteristics. The material 
presented in this paper has drawn from research from other disciplines 
and applied it to the domain of interactive cartographic manipulations. 
It is our sincere belief this initial concept will be further applied 
to enhance operations in automated cartography. 
ACKNOWLEDGEMENTS 
The authors acknowledge the support of the Rome Air Development 
Center under Contract F30602-81-C-0279. We have benefited from our 
discussions with John R. Baumann. Additionally, the assistance from 
Synectics staff and RADC Technical Library personnel is gratefully 
acknowledged. 
REFERENCES 
Cederberg, R. 1980, On the Coding, Processing, and Display of Binary 
Images, LTAB, Linköping, Sweden.