A New Approach to Automatic Scanning of Contour Maps
The problem of automatic digitizing of contour
maps is discussed.  The structure of a general 
contour map is analyzed, and its topological properties
are utilized in developing a new scanning algorithm. 
 The problem of detection and recognition of contour
lines is solved by a two color labeling method. 
 It is shown that for maps containing normal contour lines
only, it suffices to distinguish between so-called 
"even" and "odd" lines.  The "tangency problem" involved
in practical scanning is discussed, and a solution 
based on minimizing computer memory space and
simplifying control program is suggested.
CACM September, 1972
Mor, M.
Lamdan, T.
