Visual content analysis of historic functional images: Exploring colour representation on historical hand-coloured urban maps

Old maps as visual documents are significant historical records that explain
the changes within cities. However, much information has disappeared
with the lack of a professor system for collections of urban maps before the
18th century. This is true of especially coloured urban maps. This information, and the associated knowledge, could be rediscovered by analysis of
these maps. Thus, it needs methods, under the umbrella of visual analysis,
which focus on exploring graphic elements in visual resources. Thus, this
paper will discuss one of the methods for analysing the graphic elements
in historical urban maps, focusing on colour language. Using in historic
maps many elements have little contextual information due to lack records
and development of cities, resulting in alterations in maps. One example,
is the difficulty in finding the functions, materials and owners of common
buildings (e.g. houses) when compared with famous building (e.g. cathedral) in a city map. Understanding the meaning of graphic elements on
historical urban maps explores symbols, without reference to text records.
Thus, how to code and classify these graphic elements depends on visual
analysing from primary materials. Therefore, it requires the understanding
and discussion of visual content analysis to research the meanings and the
hidden information of graphic elements in historical functional images,
which have little other context. As there is a large amount of repeating
information in an urban map, it is useful to compare and summarise the
similarity, and differences, of data as systemic samples. This highlights the
function of visual content analysis again.