I loved your homage to the original mapmakers of the Ordnance Survey, giving credit to those who hauled their theodolites around the country to take their measurements (Editorial, 8 November).
Credit also should be given to the mathematicians, and especially the computers (people who did the arithmetic for hour after hour) who took the field measurements and converted them to coordinates to plot on a paper map.
I could just about cope with the sine rule and the books of log tables needed for a simple triangulation, but the computational effort needed to deal with even a simple map projection such as the Cassini-Soldner one used by the OS until the 1940s would fill me with dread. They require the use of sines, cosines and tangents in multiple calculations to get a single x, y coordinate pair.
It’s easy to praise the people who did the glamorous cartography such as displacement, simplification, drawing etc, but miss out on the hard work the surveyors and mathematicians do.
John Elgy
Redditch, Worcestershire
An Ordnance Survey map does indeed provide cultural enrichment and pleasure, as do various products of the OS shop such as puzzle books and personalised maps. However, for a deeper experience, try orienteering. It is a sport that can be enjoyed competitively, or by simply walking in a scenic setting. Events have courses suitable for all ages.
Many clubs across the UK stage orienteering events. These may take place in forests, on moorland, in interesting historic urban areas, and even indoors in an Ikea store. Many clubs offer come-and-try-it events in local parks for beginners.
Doug Edwards
Withington, Manchester
For hikers and off-roaders, Ordnance Survey maps are indeed still a genuinely useful – as well as nostalgic – way to navigate, especially using the OS’s GPS-enabled app. But their usefulness is significantly degraded by something that I only discovered (the hard way) relatively recently: that they do not reliably show public rights of way.
Only local authorities hold the so-called “definitive” public right of way route maps, more often than not in paper form only, which you can inspect only by visiting the local town hall.
More to the point, with a lack of coordination typical of the British public sector, they are under no obligation to tell Ordnance Survey if the public right of way routes change or are extinguished (which is a regular occurrence). Some authorities do, some don’t. So: caveat navigator.
Stephen Psallidas
Newcastle
Folding OS maps have a distinct role that will preserve their relevance: on the phone app, the little red arrow shows you exactly where you are – the paper map spread on the pub table later settles the argument over the mistake that got you there.
Jonathan Hauxwell
Crosshills, North Yorkshire
