I reflected recently on how technology has changed map making. In ancient times map makers had to face innumerable dangers, disease and shipwreck, in their efforts to make an accurate survey of a coastline. And mapping the interior of a country involved battling deserts, mountains and impassable rivers.

Even after the field data was collected, accurately defining the latitude, longitude and height above sea level was difficult. Small errors in the huge number of necessary hand calculations often led to inconsistent results.

Today, map makers sit in comfortable offices processing data from satellites which send a continuous stream of images. These reveal details smaller than my house. The position of any place on Earth can be found absolutely and within a few meters using a satellite system called a global positioning system (GPS). This system uses radar to look through thick clouds at the ground below and provide us with detailed images. This information can be cross-referenced by identifying common features on adjoining and overlapping pictures. Computer processing does huge calculations quickly, giving an accurate map of any place on Earth.

So next time you’re lost, be thankful that nobody was ship wrecked while producing the map that shows just where you are.