[Proj] The area of a rhumb line polygon

[Joaquim Luis]

Hi,

I just want to call your attention that GMT has the CM4 magnetic model,  
which the only one that provides an estimate of the magnetic daily  
variation, making it the best (IMO) model to use.

Joaquim


> Only the toolbox version requires R2014b.  The Matlab release I used was
> R2013a and it works with Octave too.  Just click on "Download Zip".
>
> GeographicLib already works with the World Magnetic Model 2015.  You can
> download the model from
>
>    https://sf.net/projects/geographiclib/files/magnetic-distrib/
>
> and you are good to go.  Just specify "-n wmm2015" to the MagneticField
> utility.  (This will be the default for GeographicLib 1.40 which I will
> be releasing later this week.)
>
> While on the subject of great ellipses, I provide a critique of some
> papers which advocate great ellipses for the purposes of navigation at
>
>    http://geographiclib.sf.net/html/greatellipse.html#gevsgeodesic
>
>    --Charles
>
> On 2014-12-16 09:01, Noel Zinn (cc) wrote:
>> Thanks for the Matlab versions, Charles.  Why R2014b?  (I'm still  
>> running
>> R2014a, but planning an upgrade to R2015a, which will include the new  
>> World
>> Magnetic Model.)
>> Noel
>>
>> Noel Zinn, Principal, Hydrometronics LLC
>> +1-832-539-1472 (office), +1-281-221-0051 (cell)
>> noel.zinn at hydrometronics.com (email)
>> http://www.hydrometronics.com (website)
>>
>> -----Original Message-----
>> From: Charles Karney
>> Sent: Tuesday, December 16, 2014 7:14 AM
>> To: PROJ.4 and general Projections Discussions
>> Subject: [Proj] The area of a rhumb line polygon
>>
>> The calculation of the area of a geodesic polygon has been included in
>> GeographicLib since v1.4 (2010-09).
>>
>> In the latest version v1.39, I've also included the equivalent
>> calculation when the edges of the polygon are rhumb lines.  The
>> formulation is given in
>>
>>     http://geographiclib.sf.net/html/rhumb.html#rhumbarea
>>
>> and the online planimeter
>>
>>     http://geographiclib.sf.net/cgi-bin/Planimeter
>>
>> implements this area calculation.  I've also worked out the area when
>> the edges are great ellipses.  For the formulation, see
>>
>>     http://geographiclib.sf.net/html/greatellipse.html#gearea
>>
>> An implementation is included in the Matlab package
>>
>>     http://www.mathworks.com/matlabcentral/fileexchange/47898
>>
>> Comments are welcome.
>>
>>     --Charles
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