By: Blonde Two

I like a lot of the lines on maps but I think contour lines are my favourite. Their first recorded use was by Charles Hutton in 1774 who set out not to map an area but find out how much a mountain (and then the earth) weighed! You can read more about this fascinating (and very useful) invention here but before you do, have a look at these two very different sets of contour lines. From Epping Forest to Ben Nevis, the same skills apply but the consequences of getting things wrong are probably greater on the mountain! Both maps were used for Ordnance Survey’s brilliant Street2Peak project (we love paper maps), tune it to tonight’s BBC The One Show to find out more (and possibly spot a Blonde!)