1:50 000 scale maps are small-scale maps used in our OS Landranger map series. with less detail than the 1:25 000 scale maps. At this scale 2cm on the map equals 1km on the ground or 1 1/4 inches on the map equals one mile on the ground. 1:25 000 scale maps are sometimes called medium scale maps and are used in our OS Explorer map series. They show more detail than 1:50 000 scale maps. At this scale 1 centimetre equals 250 metres on the ground; four centimetres on the map therefore represents one kilometre on the ground. Two and a half inches on the map is equal to one mile on the ground.