Football pitches, Olympic swimming pools, Nelson's Column and Wales are common visitors to news pages for reasons of comparison - as though we all go round with their dimensions clear in our minds. SubScribe suspects that most readers could visualise 100m more accurately than they could a football pitch - and certainly a quarter of a mile more easily than four football pitches. We can create our own comparison: the distance to the pub, the bus stop, the corner shop or whatever.
Bigger areas pose a bigger problem. The hunt for the missing Malaysian airliner was at one point focused on "an area the size of Alaska". How big is that? How many Waleses, for example? And, for that matter, how big is Wales? SubScribe would love to hear suggestions for more sensible yardsticks.
In the meantime, a football pitch is between 90 and 120m long; an Olympic swimming pool is 50m long and contains about 2.5m litres of water; Nelson's Column is 52m high (so roughtly an Olympic pool or half a football pitch turned on its end).
Wales is just over 8,000 sq miles; Alaska is 663,000 sq miles, so about 83 Waleses or - just to add to the confusion - two Texases, or about 10% of Russia.