Sunday, June 29, 2014

1923 Manchester Ship Canal strip mapStrip Maps of the Manchester Ship Canal

I am a big fan of unusual modes of mapping. One cartographic design approach that has long fascinated me is the linear route chart, known as the 'strip map'. A few years ago for my PhD research I wrote a draft chapter considering how the process of data routing through the Internet could be represented using the strip map concept, and also thought of as a kind of 'Songline'. (Somewhat sadly, this work did not make into the finished thesis as it was not deemed worthy by my PhD examiners!)

Anyway, the cartographic scholar Alan MacEachren has also written some key articles describing the nature and utility of strip maps a couple of decades ago. In particular, he usefully delineated the essential characteristics of strip maps in his 1986 article, setting out a five-level schema of ‘stripness’:
  1.  linear form omitting geographic detail beyond a narrow route corridor,
  2. orientation with a direction other than north at the top, not orientated along a cardinal direction, 
  3. lack of concern with geographic orientation; no indication of cardinal directions given,
  4. relaxation of planimetric accuracy to allow variations in scale and orientation between different parts of the map so as to maintain the linear format of the route,
  5. strict linear representation of route way with complete disregard to consistent scale or direction.
    The strip map can be a very effective means of representing long complex routes in a clear fashion by eliminating a lot of extraneous detail. Despite its utility it is not a widely seen mode of mapping but examples can be found throughout cartographic history, including some ancient Roman examples and well known pilgrimage charts from the medieval period. The strip map came into its own with the development of better transportation from the eighteenth century onwards in terms of displaying turnpike roads, canals and railway lines. The different contexts in which the strip map has been deployed are well documented in another paper by MacEachren and his Johnson.

    Interestingly multiple versions of strip maps were also published through the twentieth century by the owners of the Manchester Ship Canal to promote its facilities. The linear nature of the 36 mile long canal made it well suited to being displayed in abstract form that eliminates much geographical reality for sake of clarity. The first example map, shown above, is from 1923 and represents the Ship Canal as a dead straight orange line from the Mersey down to Manchester Docks. All the locks and different bridge crossings are neatly delineated, along with small icons locating important canal side industrial facilities, such as Robertson's Steel Works at Thelwell. (The location of Lymm golf course is also shown for some reason.) Wider loops of the older Bridgewater Canal the River Mersey that accompany the MSC are also depicted.

    The second example, shown on the right, is a somewhat more simplified in informational content and also slightly less 'strip' straight, with the cartographer choosing to represent at least some of the sinuosity of the canal's real geography. The result is rather cartoon like, in keeping with its role as the key illustration in a tourist leaflet to guide people taking an 'educational cruise' down the Manchester Ship Canal in the mid 1960s. (This image is scanned from an original copy of the leaflet in the Brian Robinson Archive, courtesy of Lloyd Robinson.)

    Manchester Ship Canal strip map, 1970s?
    On the left is more contemporary version, described as a 'diagrammatic map', which is packed with textual description parallel to the artificially straightened blue Manchester Ship Canal channel. (Indeed, the map component seems rather constrained by the more verbose text, making it less aesthetically pleasing chart than earlier examples.) Again the multiple crossings and locks along the MSC's full length are carefully denoted from Eastham locks on the Mersey Estuary downwards. Compared to earlier examples, the Queen Elizabeth II oil dock at top of Canal, newly built in 1954, provides a somewhat odd looking addition. There is little coverage of the Bridgewater Canal on this strip map, reflecting its diminished status as a transport route by the post-war period.
    If you want to see these three example charts in more detail, I have put them together into single pdf: Manchester Ship Canal strip maps.

    Further reading:

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