[R-sig-Geo] World map in magnetic coordinates

[Clint Bowman]

Why not plot data and map in original coordinates and then overlay 
with grid lines showing magnetic coordinates?

-- 
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On Fri, 8 Oct 2010, Barry Rowlingson wrote:

> On Fri, Oct 8, 2010 at 7:21 PM, ogbos okike <ogbos.okike at gmail.com> wrote:
>
>> library(maps)
>>  data(worldMapEnv)
>>  map("world")
>> The three steps above in R gives you the world map I mean.
>
> if you do:
>
> w = map("world")
>
> then w will be a simple list with $x and $y components, as well as
> $range and $names. If you write the $x and $y to a file, convert, then
> read back into $x and $y (and then convert the $range, which is the
> bounding box) you should have something you can plot in transformed
> coordinates.
>
> Note that polygons are separated by an NA in $x and $y, so you will
> have to make sure you preserve those too.
>
> Barry
>
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