In a previous blog post, The head of the cartographer, I discussed the role of the cartographer in the creation of the map. I pointed out that everything from the landscape was filtered through the cartographer’s interpretation. Thinking and embodied acts are key to the creation of maps, not only because the surveyor move around in the landscape but also because the cartographer at the drawing desk use his or her body and mind in the map creation process.
This month I will look into a slightly different process. Not the one from landscape to map but the one from texts and vector data to maps. The former process takes as a starting point a landscape which is not fully defined by humans, however modified it may be by humans, and makes a map based on it. It is a process from a real landscape to a media product. The landscape is categorically different from the map.
The process of creating maps based on texts or vector data is fundamentally different because the sources for the maps are already information objects created by humans, although often with the help of computers. They are media expressions, and thus, categorically similar to the map. Categorically similar, yet quite different.
A map image adheres to the semiotic language of the indexical grid. The relationships between signs are based on geometry. The geometry of the map expresses statements making claims about real world geometry. Texts and sets of vector data, on the other hand, both refer to the external world in a different way, using symbolic expressions of relationships.
As an example we will look at various ways of expressing a spatial relationship in the municipality of Tydal in middle Norway. Example 1 shows how it was expressed by a text taken from Peter Schnitler’s Border Protocols from 1741 (page 54 in the printed edition from 1962, Major Peter Schnitlers Grenseeksaminasjonsprotokoller 1742–1745).
(Example 1) The road to Jemteland the ordinary one goes from Østbye Farms to Øye mountain can be estimated 1 new mile
(Example 2) Østbye: (331584.234, 6995927.508).
Øye: (339750.547, 6996720.867)
In vector data the relationship will be expressed differently. There is no explicit from and to in the vector data in example 2 (expressed in UTM zone 33, EU89). The relationship is not expressed as an explicit relationship between two places. Each of the places will have a location in the coordinate system, expressed by co-ordinates—one for each place in this case, as the places are expressed as points; in the case of lines or polygons a series of co-ordinates is needed.
The spatial relationship between places is inherent in the geometry expressed in the vector data. The same can be said for a map. A modern map including the two places can be found in figure 1. Again, there is no explicit link between the places but a claim for the spatial relationship between them is expressed in the geometry of the map.
Based on the text alone, also Figure 2 is a true map (or rather network diagram) if we see the text as decontextualised, outside the context of representing a true historical landscape. If we include the contextual understanding of the landscape, Figure 1 is truer. Yet, it is not fully true. The map includes many features we know was not there in 1741, and features we suspect may have changed. Figure 2 represents a more limited view and in that sense it expresses nothing which is not stated in the text.
I pointed out the interpretative relationship between a landscape and a map above. A similar interpretative relationship is clearly present when a map is made based on a text, or when a pre-existing map is selected to represent a landscape described by a text. The choice between figure 1 and 2 as a representation of example 1 is based on an understanding of the meaning of the text, its context, and the use the figure is to be put to.
The same can be said for the vector data in example 2. The choice of those two coordinates to represent the textual information is based on human interpretation and an understanding of text and context. The same can be said for the choice of points and not polygons to represent the two places. These choices have consequences for future use of the vector data, but they are also in part steered by what is know and what can be known. While the area covered by the Østbye farms could in principle be known from historical property documents, the area of the mountain is unknowable. Farms may have legally defined borders, whereas no similar borders exists for mountains such as this one.
Creating a map based on vector data is different in principle from all the relationships described above. While a set of vector data can be used to create quite different looking maps, and through that, maps with different levels of usability for different purposes, there is no real geometrical leeway from vector data to map. So the location of the two places is fully defined and no human intervention is needed or even applicable in the process of drawing out the map. This is the reason why the drawing of a map based on vector data is a fully automatic process once the stylesheet and the scale is chosen.
|From landscape||From text||From vector data||From map|
|To text||interpretation needed||interpretation needed (except copying)||?||interpretation needed|
|To vector data||interpretation needed||interpretation needed||?||?|
|To map||interpretation needed||interpretation needed||interpretation not needed||interpretation needed (except copying)|
We see in table 1 that only when vector data is used to create a map can we do without geometrical interpretation in media transformations. Note also that when transforming between expressions in the same medium, we can do without interpretation when copying, as we saw for maps in an earlier blogpost. We may also see the same as in copying when we do systematic rule based changes to a text or a map in order to create a new expression in the same medium.
I also added to the table some transformation I have not discussed in the text above. I hope I will be able to get back to those in later blog posts.
2014-10-31 Øyvind Eide