Vistors to the Anvil Point area of Durlston County Park may be surprised to see two tall, metal posts high on the hill facing out to sea. These mark the eastern limit of a ‘Measured Mile’ and an identical set of markers can be seen exactly one nautical mile to the west. The mile starts when the two posts are exactly lined up one behind the other when viewed from the sea and finishes when same hapepns at the other end.
© Copyright Nigel Mykura and licensed for reuse under this Creative Commons Licence
Despite advances in technology, ships still use the markers for timed sea trials. To offset the effects of tide and weather, several journeys are made between posts to obtain an average reading.
A similar system exists on the Thames where pleasure craft can check their speed by passing two sets of markers. Under a minute to pass and they are breaking the 8 km/h river speed limit whereas a minute or over is OK. For the mathematically minded, 8 km per hour is the same as 133.3 metres per minute, so the markers are set 133m apart.
Although we use the Swanage mile markers as reference points when we need to, we don't get so many jobs on the Thames.
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