Interactive graphics: analytical tool for geoprocessing Page: 8 of 17
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polygon around his area of interest. On command, PTOLEMY compares the search
polygon with each of the entities displayed on the screen to produce a new map
file. The new map file contains only geographic entities from the original map
which overlapped the search polygon. The new map is displayed on the screen
. ata scale that fills the screen. In effect; PTOLEMY zooms in on the map
data within the search polygon while maintaining all linkages to the data in
the application files. This new map file is retained in the cartographic
data base until specifically discarded by the researcher. If desired, the
researcher may use this new map to zoom in again or he may choose to continue
with another map in the data base.. The researcher may zoom as many times as
desired (within the limits of disk file storage space), or to any level of
detail (within the limits of the data resolution).
The zooming process is also used to construct a new map from pieces of
existing maps. Zooming is performed once for each piece of an old map that is
desired. Instead of building a new map file for each zoom, the pieces are
collected into one composite map.
When the new map meets the researcher's satisfaction, PTOLEMY will produce,
on command, a data listing from the application files. The data linkages,
which were maintained in the zooming process, are followed to retrieve the
application data which corresponds to the new map.
PTOLEMY is also designed to produce maps as a result of content retrieval
from the application data files. The researcher specifies the item (data field)
of the application file and the desired value.- PTOLEMY searches the appli-
cation file for items with the specified value. When one is found, the linkage
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Hill, E.R. Interactive graphics: analytical tool for geoprocessing, article, January 1, 1973; Richland, Washington. (https://digital.library.unt.edu/ark:/67531/metadc1058972/m1/8/: accessed May 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.