Maps and Schematics
If a cartographer or GIS analyst were asked to create a map of an urban metro system, their instinct might be to create something like this representation of the London Underground:
This map is pleasing to the eye and geographically relevant, but not completely useful for its presumed primary use-case, that being using the London Underground for travel. In the GIS world we think of data as thematic layers of geospatial information fixed to points on the earth, and this is how we build maps "up". In that sense, this is indeed a faithful representation of the Tube network.
And while this map is useful for understanding where Underground stations and lines can be found, it is much less useful for knowing how to use the system to get around London, unless you don't happen to need to change lines on your journey. At the end of the day, most maps are meant to be used for something, even if nice ones do also fulfill a secondary role for map-lovers as being works of art!
If this map was meant to be a travel guide, it actually presents one particular level of detail that is almost surely irrelevant to its primary use-case: it shows exactly where on - or under? - the earth the metro lines can be found. Almost all maps are meant for communication, and showing unnecessary or distracting information can be counterproductive to that communication.
Most people interested in seeing a "map" of a metro system are actually interested in seeing a schematic of the metro - specifically a geoschematic - even though they may not know the word. To use the metro network they need to understand the relationships between stations just as much as knowing where they are. A schematic might only show those relationships and a schematic per se can show any kinds of relationships. A geoschematic is a compromise and attemps to show these relationships in a vaguely geographical context; but leaves it to a "map" (i.e. cartographic representation) to show exactly where those stations can be found.
Knowing where the stations are in relation to surface features is also necessary, but here a second traditional cartographic map showing stations, but without the clutter of showing the underground lines, is more useful. The mock-up below shows the respective role of each type of visualisation.
The classic metro network map is a geoschematic and I personally I find it interesting that all people intuitively find this kind of geoschematic representation of a transportation network to feel "natural". In other words, our innate need for spatial orientation craves a visualisation and representation that is use-case appropriate; in this case that of the relationships between the key access points of the network: the stations. This could harken back to pre-historic people drawing simple geoschematics in the sand to show others where food or enemies could be found and the paths to those things as straight lines.
Bees may also be communicating a kind of map or schematic when they do their "waggle dance", suggesting that it is not only humans who use maps --- but that's a topic for another day!
In those geoschematics only relevant features would be shown and the basic landmarks to get there, and those features only shown with in their relative geographic positions.
In addition to transport network visualisations like the famous London Underground* "map", other types of networks are also suited to schematic representations of various types - geoschematics, hierarchical schematics, etc. I have spent many years working with telecoms and utilities networks and here the schematic representations of these media networks are by far the most important to many teams in those organisations. The geographic or "map" view is of course important for physical planning, engineering, build and maintenance of the network; but the visualisation offered by schemtics of the topological and hierarchical relationships within the network - the relationship between supply and consumption points of whatever it is - a broadband signal, water, electricity - as well as the places where that "flow" can be controlled (e.g. valves, switches, splices, etc), is what is more relevant to other teams, in provisioning, marketing, outage management and others.
*Sidebar: there is a fantastic display of many different kinds of maps of - and attempts to communicate - the London Underground at the London Transport Museum.
It's about communication and the visualization that suits that use case. We'll cover more on this specific area in an upcoming blog, soon!
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