Back on the Essex prairies, I take photos now specially for the Ordnance Survey map of Britain, so people click on a place and all our pictures come up. Contributors collect points for them all, and the map has 100km squares with two letter codes (I live in TQ), and each gets a point as well. The most efficient way to do it is to go to an intersection where four squares meet, assuming the sea isn't in the way as it is on the south side. That happens to be on the Essex marshes to the east, which was why I went there for only the second time in my life, but as no commonly used maps have the roads there (they are dead ends and then become private land) I printed something out and drew the route on it from the only very dodgy source I could find online. I went to the node point and when I turned right at the crossroads to reach both new squares went from a farm to a grass track where the road I expected was over a mile long.
It was obvious it wasn't going south to the next square, but as the crossroads on the map was in square one I drove a couple of miles south and entered square two from the west, and when I got home and compared my results with the map discovered two crossroads where my printout had one. The first had a tiny dead end on the left and the farm entrance on the right, the real road was half a mile further along. But both didn't have a straight ahead as the major road I was on already turned left only on both, which is extremely unusual once, and almost unheard of for two junctions in a row.
So after a demanding trip (you have to drive almost 20 miles through all the suburbs with nothing but traffic lights before you reach the open road) I simply had to do it again as the sea makes both these squares much further away from anywhere else- I'd already tried to get one using the route NE and turned back due to the worst traffic jam I've ever seen on a major road so although I only needed the northern of the two there wasn't anywhere for some miles northeast besides the exact darn place I'd aimed for already. Six days later I had a free day, and for the third time (the first was to the seaside last month further south) took the only road east (the other is much further south and only a basic A road) and actually had no traffic, continued to the crossroads I needed, did the exact route planned first time, and then a small run north and back west to cover more new ground for my map. It did mean I took the little route south into the first new square I'd never have bothered to otherwise, and a few to the north I wouldn't have done had I done it in one, so did get a small bunch of roads rather than a single line which has at least beefed up a corner of my map which wouldn't be otherwise.
I posted in their forums for the biggest cockup on a photo trip, and easily trumped by someone who drove from Yorkshire to Heathrow to take someone to the airport, and planned to photograph most of the road back, only to find he'd left his camera at home. I would always buy one if that happened to me as long as the shops were open, as for £30 or so you can cover yourself easily and always need a spare, but he didn't. Anyway, for a change you have the story behind one of my trips, and nowadays most are to work my way round the compass points and almost done them all now as there are only so many.