Research and Advances

A hash code method for detecting and correcting spelling errors

The most common spelling errors are one extra letter, one missing letter, one wrong letter, or the transposition of two letters. Deletion, exchange, and rotation operators are defined which detect and “mend” such spelling errors and thus permit retrieval despite the errors. These three operators essentially delete a letter of a word, exchange two adjacent letters, and rotate a word cyclically. Moreover, the operators can be used in conjunction with hashing, thus permitting very fast retrieval. Results of experiments run on large databases in Hebrew and in English are briefly indicated.

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Research and Advances

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.

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