5. A method according to claim 4 further comprising the step of: if a b 0-cell in a dot-file belongs to two different chains, forming a record of a grid file having the following format: EQU &lt;amended group2&gt;&lt;A/B&gt;&lt;chain1 chain2&gt; . . . &lt;index1 index2&gt;&lt;cell id&gt;.
6. A method according to claim 5, further comprising the steps of: a. if there are records in a grid file, one from map A and one from map B with the same pair of groups, forming a track-file by combining pairs of records of grid-files wherein records in the grid files of each of the maps has the following format: EQU &lt;group1 group2&gt;&lt;A&gt;&lt;chainA1 chainA2&gt; . . . &lt;indexA1 indexA2&gt;&lt;cell A&gt; EQU &lt;group1 group2&gt;&lt;B&gt;&lt;chainB1 chainB2&gt; . . . &lt;indexB1 indexB2&gt;&lt;cell B&gt;; the two track-records corresponding to the same intersection have the following format: EQU &lt;chainA1 chainB1&gt;&lt;indexA1 index B1&gt;&lt;cell A cell B&gt; EQU &lt;chainA2 chainB2&gt;&lt;indexA2 index B2&gt;&lt;cell A cell B&gt;; b. labeling those chains which belong to more than one group in order to prevent formation of numerous false potential matches; and c. sorting the resulting track-file lexicographically.