About this programme

9/9. Nicholas Crane explores the most treacherous terrain in Scotland as he attempts to retrace the steps of the makers of early Ordnance Survey maps, dating back to the 1930s. Using the same triangulation systems, he tries to find the heights of mountains, and enlists the help of an RAF fighter jet to show how accurate the pioneering surveying team was, even when its members had to make observations at night. Last in the series.