As a rule digitalization packages work with the source cartographic material represented in the form of separate pages. ObjectLand supports the model of a continuous map. Thus, after import it is necessary to perform sewing (combining) line and area features of the same type parts of which were located on neighboring pages.
Sewing operation allows sewing two area or two line features into one if their boundaries touch each other. However, when performing digitizing it is difficult to guarantee precise coincidence of coordinates of one and the same point. That is why not precise touching of boundaries is checked during sewing, but their neighborhood within some rectangular area called sewing region.
An example of performing sewing is shown at figure 75-1.
Figure 75-1. Example of sewing features
It may happen so that sewing can be performed incorrectly: the features which should not be sewed are sewed or on the contrary, the ones that should be sewed are not. Correctness of performing sewing operation mainly depends on two factors: quality of source data, that is, digitizing precision, and selected width of sewing region. In case of unsuccessful sewing the system provides the user with a possibility to perform rollback – return the map to its initial state using the rollback file.
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