Postby Chris Jeggo » 20 Feb 2012, 4:25pm
The bottom line IS at the bottom, if you want to skip the following discursions of a map "anorak".
There are three issues here - scale, accuracy and the representation of relief.
Possibly the most important aspect of accuracy is the representation of roads (I am not considering off-road cycling here) and in particular whether they are metalled. The OS 1:50000 maps (and their predecessors, 1:63360 or 1"=1 mile) show all tarmac roads in yellow, while their "white" roads could be anything from a tarmac private drive to an atrocious, rutted and overgrown tractor track. The OS 1:250000 maps show all tarmac roads - if it's on the map it's tarmac, and if it's not it's not. Both of those systems are acceptable. However, Bartholomew's "white" roads might be tarmac or might not, and you never knew until you got there, so this was not satisfactory.
Bart's maps may originally have been based on OS mapping, but when I became keen on cycle touring and joined the CTC in 1974, W Surrey DA had a Map Officer whose job it was to collate members' corrections to Bart's maps and submit them to the publishers for incorporation in later revisions. OS revisions did not automatically appear on Bart's maps, which as a result gradually became more and more inaccurate. So although I was very pleased, as a schoolboy in the early 1960's, with the first map I ever bought, a Barts "half-inch" of my local area "Vale of Trent", by 1974 the Bart's 1:100000 sheet "Surrey" was simply not accurate enough, and ever since then I have used OS maps. I use 1:50000 maps most of the time. On the other hand, 1:250000 is very good for planning and for long tours - they were great for LEJOG - and layer tinting is a great way to represent relief. I was very sorry to discover recently that they are no longer published.
The mid-1970's were also when UK mapping went metric. The OS went from "one inch to one mile" to 1:50000, and Barts brought out their 1:100000 National Map Series using the same sheet lines as their former "half inch to one mile" maps. Both organisations chose this time to make their maps "clearer", which would have been achieved anyway simply by the change of scale, but they both reduced the amount of information provided, by too much in my opinion. For example, OS stopped distinguishing between different types of woodland. Barts, previously, had shown inns, but not all watering holes appeared and some that did were long closed. Bart's solution to this problem was simply to stop showing inns, instantly making their maps less useful. Since then, OS has restored some detail in response to user feedback, while Barts simply died.
For the representation of relief, contour lines are most precise while layer tinting is very good for rapid visualisation of the lie of the land. Contour lines must not merge (but they are allowed to disappear at cliffs and quarries) so they are further apart vertically on smaller scale maps. The contours that are the boundaries between tint layers need to have an even greater vertical interval. However, the two systems can be, and often are, combined. Bart's layer tinting used to be superb, and OS's was too back in the 70's, but they have since reduced the number of layers and reduced the saturation of the colours, making it difficult, except in good light, to distinguish between some layers.
In my opinion a scale of around 1:100000 is ideal for road cycling. You need too many maps at 1:50000, and there is not enough detail at 1:250000. If Barts had solved their accuracy and "clarity" problems they would still be the maps of choice. It should be feasible to include off-road sections of official cycle routes (e.g. Sustrans NCN), but it is not realistic to expect much more at this scale. The OS "Tour" series at around the same scale is dying because OS aimed them at motorists (who buy atlases rather than maps) and missed the chance to optimise a product for the users who are most interested in that scale. I bought the "Tour" map of Surrey when it came out, and realised as soon as I studied it in detail at home that I had wasted my money. The representation of roads and relief is exactly the same as on the 1:250000 maps - it's just printed bigger. What's the point of that?
Interestingly, I have an OS Half-inch Tourist Map of Snowdonia published in 1979. It is brilliant! The representation of roads is good, and the more important walking routes are shown too. Contours are at 100ft vertical interval and are combined with superb layer tinting. OS can do it! So why don't they?
It is interesting to compare UK mapping with French. The French equivalent of OS, IGN, publishes topographical maps at 1:25000, which are excellent for walking, and 1:100000, which are excellent for cycling, so they don't bother with 1:50000. Both series show relief by contours. The best maps for the next smaller scale are the Michelin 1:200000 ones. They are distinctly poor at showing relief but are very good otherwise; I certainly like the green side-lining of scenic/picturesque roads. So when touring in France I carry either Michelin maps or pages torn from Michelin road atlases in addition to the IGN maps.
As for which maps to buy, I cannot do without the 1:50000 Landranger series. For smaller scales many turn to road maps or road atlases, which mostly do not portray relief. The main exception is the Philips atlases, which are based on OS mapping. One is at 1:200000 based on 1:250000 OS mapping while their "Navigator" is mainly at 1:100000 and based on larger scale OS mapping. I have just checked the preceding information on the internet and was surprised to find that Philips also sell "Navigator" regional and county maps at 1:100000, £3.99 per sheet at Stanfords. I had never heard of them, so I shall investigate them as soon as I can.