# Re: OT Re: Constructed maps

From: | Lars Finsen <lars.finsen@...> |

Date: | Tuesday, January 15, 2008, 14:28 |

ROGER MILLS wrote:
> quoting BP Jonsson:
>>
>> I get zilch of the math though! :-)
>
> Concur, unfortunately............

But wasn't you the one who asked for formulas?
If you do want to make hand-drawn wedges for your globe, it's not
hard to calculate from the formula if you have a hand calculator with
a cosinus function. Or you can use the one in MS Windows Utilities or
Mac OS X Utilities or whatever is applicable for you. Alternatively
you can try to dig up a book of trigonometrical tables and do the
calculations by pen and paper. We live in 2008, don't we? It means,
everything is possible. Yours is the choice.
You can use ordinary graph paper for plotting. Draw an x-axis
horizontally along the middle of the sheet lengthwise. Its length
should be 0.5 times pi times the radius of the globe. 3.14 for pi is
fully sufficient for these calculations I think. Some calculators
have a pi key giving you the number.
At reasonable intervals along the x axis, say half a centimeter or
thereabouts, calculate the y value by dividing first x by r, the
radius of the globe, take the cosine of this value (remember that the
calculator should calculate in radians - many have a switch to
exchange degrees to radians and vice versa), multiply this by r and
then by pi, and divide the result by n, the number of wedges. Stepwise:
1.divide x by r
2.cosine the result
3.multiply by r
4.multiply by pi
5.divide by n.
Then you should get a distance to plot above and below the x-axis,
and when you have made all the points from the start to the end of
the axis, you can draw a line connecting them, and then you will have
a fine template for your wedges, if I have done my maths right. I
haven't tried it myself.
Alternatively you could enter the formula into MS Excel or a similar
spreadsheet, ask it to make a graph out of it and print out the
graph. But the other method will work just as well. And be more fun,
at least in my opinion...
LEF