It should be noted that if several rollback files were created as a result of several sewing operations, for correct restoring of map features using these files rollbacks should be performed in the order reverse to creating these files. Rollbacks in arbitrary order will not lead to disastrous effects but most probably not all the map features will be restored to initial state. Forming rollback files when two sewing operations are performed one after another and results of correct and incorrect rollback operations in such a situation are shown at figure 75-8, 75-9 and 75-10.
Figure 75-8. Creating rollback files in successive sewing
Figure 75-9. Correct sequence of rollbacks
Figure 75-10. Incorrect sequence of rollbacks.
Judging from the above said one should treat the possibility of appending data to one and the same rollback file very carefully when performing several sewing operations. To provide correct sequence of performing rollbacks it will be safer to create a separate rollback file for every sewing operation.
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