Example of spatial aggregation-generalization mismatch where aggregated
data provide true data but unreadable map while generalized data produce
readable map but inexact data
06 B?©dard, Rivest, & Proulx
Copyright ?© 2007, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of
Idea Group Inc. is prohibited.
data never fit together or with reality! This creates major challenges for SOLAP as
explained later in this chapter.
In addition to the preceding issues, when one needs to have a more global cartographic
view of a phenomenon, it is not possible to simply aggregate spatial data
since the map or display becomes overcrowded and unreadable. One must rather
use map generalization processes. According to Weibel and Dutton (1999, p. 126),
???Map generalization is responsible for reducing complexity in a map in a scale
reduction process, emphasizing the essential while suppressing the unimportant,
maintaining logical and unambiguous relations between map objects, and preserving
aesthetic quality.??? Every map, including the map made from source data, uses
some level of generalization. By definition, a map is a model of only a subset of
the reality where unnecessary details are eliminated and useful data emphasized
while maintaining the map readability. Going from a large map scale to a smaller
map scale worsens the situation.
Pages:
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559