I’ve walked most of my life using OS maps and, like most others, considered them to be “the bible”. However, I’ve been using GPSs for many years (years before I discovered geocaching) and the thing that struck me immediately, was just how inaccurate OS maps are. There was no way of questioning their accuracy before, although you often had a feeling that they were wrong, but with a GPS you then knew they were wrong. I download all my tracks from my GPS onto Memory Map and am still surprised at the OS errors I find. Most notably is the completely inaccurate location of the crossing point of the Two Moors Ways with the B3212 and the positioning of the 2 car parks at Bennetts Cross – these are approx 200m wrong! Also the Cairn Circle and Cist at Skir Hill (near my cache) are nearly 200m out on the OS map, which completely threw me on my first walk there, prior to placing the cache. Also the crossing point of the Dartmoor Way and the bridleway running between Whiteworks and Sherberton is nearly 300m out! I don’t think these are due to “drift” but to really bad and lazy cartography. This is particularly noticeable with the newer green rights of way, which are often wildly wrong, whereas the original little, black, dotted lines are often totally accurate. However, I also really love OS maps and can spend hours pouring over them, so I can’t be too critical!