  Are nearby places (e.g. cities) described by related words? In this article
we transfer this research question in the field of lexical encoding of
geographic information onto the level of intertextuality. To this end, we
explore Volunteered Geographic Information (VGI) to model texts addressing
places at the level of cities or regions with the help of so-called topic
networks. This is done to examine how language encodes and networks geographic
information on the aboutness level of texts. Our hypothesis is that the
networked thematizations of places are similar - regardless of their distances
and the underlying communities of authors. To investigate this we introduce
Multiplex Topic Networks (MTN), which we automatically derive from Linguistic
Multilayer Networks (LMN) as a novel model, especially of thematic networking
in text corpora. Our study shows a Zipfian organization of the thematic
universe in which geographical places (especially cities) are located in online
communication. We interpret this finding in the context of cognitive maps, a
notion which we extend by so-called thematic maps. According to our
interpretation of this finding, the organization of thematic maps as part of
cognitive maps results from a tendency of authors to generate shareable content
that ensures the continued existence of the underlying media. We test our
hypothesis by example of special wikis and extracts of Wikipedia. In this way
we come to the conclusion: Places, whether close to each other or not, are
located in neighboring places that span similar subnetworks in the topic
universe.
