Algorithm and visual realization of auto-retrieving the new and old sheet numbers of topographic maps

On the basis of comparing the difference between those two map numberings, This work presented a particular algorithm of auto-retrieving the new and old sheet numbers of a certain assigned region and of a certain assigned scale, that is, basing on scale of 1:1000000, we enumerated all the four kinds of distributions on its sheet partition in terms of the longitudes and latitudes at the top-left and bottom-right corners of the assigned rectangular region, and then refined the sheet partition mentioned above according to actually scale we used. Thus, a duplicate traversal throughout all map sheets of assigned scale covered by the assigned region had been accomplished; meanwhile, all desired sheet numbers were obtained. Furthermore, with VB (Visual Basic) and MO (MapObjects), a software with spatial query interface had been developed and put in use as a visual realization of this algorithm. With it, users can quickly get all sheet numbers of certain regions just by selecting them with the mouse. Results show that this application brings average users great convenience in topographic map researching.