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Help the innumerate: map scales

  • 05-07-2005 4:01pm
    #1
    Yoda
    Registered Users, Registered Users 2 Posts: 1,853 ✭✭✭


    I thought about posting this to the Mathematics forum, but figured that the Weather forum would enjoy it more.

    I have an 1842 map of Mayo with a scale legend of 1 inch = 10 Irish miles. What is its scale?

    1 inch = 25.4 mm.
    1 Irish mile = 2,240 yards = 2,048.256 m = 2,048,256 mm
    10 Irish miles = 20,482,560 mm

    20,482,560 mm ÷ 25.4 mm = 806,400.

    Is the scale 1:806,400?
    Or am I hopelessly innumerate?


Comments

  • #2
    Mothman
    Closed Accounts Posts: 6,498 ✭✭✭Mothman


    Yoda wrote:
    I thought about posting this to the Mathematics forum, but figured that the Weather forum would enjoy it more.

    I have an 1842 map of Mayo with a scale legend of 1 inch = 10 Irish miles. What is its scale?

    1 inch = 25.4 mm.
    1 Irish mile = 2,240 yards = 2,048.256 m = 2,048,256 mm
    10 Irish miles = 20,482,560 mm

    20,482,560 mm ÷ 25.4 mm = 806,400.

    Is the scale 1:806,400?
    Or am I hopelessly innumerate?

    Is an Irish mile the same as a Mayo mile :D

    FWIW, you are right, but you didn't have to go into mm to work it out ;)

    36 inches in a yard.
    2,240yards = 80,640 inches * 10 miles = 806,400 (as above)


  • #3
    Yoda
    Registered Users, Registered Users 2 Posts: 1,853 ✭✭✭Yoda


    Huh. Well, OK. Thanks. I've got some other maps here, an 1837 map of Wicklow which looks like it wants to be 1" = 4 Irish miles though the drawn scale rule is about a mm shy of a real inch. I'm calling the scale 1:322,560 anyway.

    Then there's the 1761 map of Portugal, which has the lovely scale of 18mm = 70 English miles = 25 French leagues. I'll calculate and see what I get, after I find out how many mm in a French league....


  • #4
    Yoda
    Registered Users, Registered Users 2 Posts: 1,853 ✭✭✭Yoda


    Well... there are several versions of French league, according to the French Wikipedia. There's a metric one (1 league = 4 km), a terrestrial one (1 league = 4.4448 km), and two others.

    So ignoring those, and assuming that an English mile in 1761 is the same as one today, the scale is 1:1:6,258,560


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