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RE: Measuring the area of a valley from osmaps

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  • 05-08-2010 4:17pm
    #1
    ben2010
    Closed Accounts Posts: 1 ✭


    Hi All,

    Does anyone know how I would measure the area of a valley from an OS map or if there is a software programme or could recommend somewhere/one that could do so?
    I am doing a thesis and I do not have a geography or mathematical backround but I just need to know the area in order to move to the next stage, again I dont want to have to purchase anything expensive or anything at all preferably as I only need to know this.

    Thanks

    Ben


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    #2
    YoureATowel
    Closed Accounts Posts: 85 ✭✭YoureATowel


    ben2010 wrote: »
    Hi All,

    Does anyone know how I would measure the area of a valley from an OS map or if there is a software programme or could recommend somewhere/one that could do so?
    I am doing a thesis and I do not have a geography or mathematical backround but I just need to know the area in order to move to the next stage, again I dont want to have to purchase anything expensive or anything at all preferably as I only need to know this.

    Thanks

    Ben


    Are you trying to measure off a paper map? Once upon a time area was measured off paper maps using a device called a planimeter. Since the introduction of digital mapping these devices have become outdated so it would be fairly hard to get your hands on one today.

    These days, with digital maps and GIS software, a task such as this is as easy as they come. I'm assuming you have access to neither. If so try this method.

    Go to OSI Mapviewer and find the valley on question. Move your cursor around the boundary of the valley in a clockwise direction and at sufficient intervals take a note of the XY coordinates at each point.

    The first point will be X1,Y1 the second point will be X2,Y2 and so on until you close the loop with a last point Xn,Yn.

    Now the formula to compute the area is

    2 * Area = (X1Y2 + X2Y3 + ....... + XnY1) - (Y1X2 + YxX3 + ...... + YnX1)


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