The problematic interpretation of old planning maps as historical sources
This general difficulty becomes even more problematic in the field of spatial planning in which maps are used to propose spatial interventions. These kinds of maps are a complex mixture of ‘reality’, ‘knowledge’ and ‘imagination’. This can be illustrated with the help of one of the first maps made by the Dutch engineer B.P.G. van Diggelen in 1849 as part of his plan to dam and drain the Zuiderzee. As will become apparent, it is especially the dividing line between ‘fact’ and ‘fiction’ that becomes problematic from a historical perspective.
First of all, regarding the geographical situation, maps are a selection and thus simplification of reality. If this selection is based on a scientific method the map can be seen as the epistemological rendering of reality. Second, the interventions also represent a form of knowledge; whether technical, administrative, legal or social. Often, the visual representation of these interventions includes specific conventions and rules for depicting elements and in that way, informs the reader about their status. For instance, dotted lines are often used for proposed construction works. Third, a map is also the product of the creator’s own imagination.
Analytically, these dimensions can be separated. However, to operationalize them, in the sense that they can be used for the interpretation of planning maps as historical sources, is quite problematic. This is due to the fact that these dimensions blend when put together on one map. This can be illustrated by zooming in on specific elements of the map of Van Diggelen (figure 2).