Calculating area of latitude-longitude quadrangle?

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Is there any way to calculate the area of a latitude-longitude
quadrangle in IDL, or some formula I could use?
MATLAB can (using areaquad from the Mapping Toolbox, which can return
surface area in km^2 of a lat/lon box covering a part of Earth) but I
do not have access to MATLAB.
0
Reply ashley.berg (12) 8/23/2011 6:52:06 PM

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Ashley Berg writes: 

> Is there any way to calculate the area of a latitude-longitude
> quadrangle in IDL, or some formula I could use?
> MATLAB can (using areaquad from the Mapping Toolbox, which can return
> surface area in km^2 of a lat/lon box covering a part of Earth) but I
> do not have access to MATLAB.

Wow! Really!? 

I'm not sure I'd put a whole lot of trust in a 
number like that! :-)

Cheers,

David 



-- 
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
0
Reply news8567 (866) 8/23/2011 7:13:46 PM

Yes, I'm not sure exactly how MATLAB does it!  But for my purposes I
only need a rough estimate.
0
Reply ashley.berg (12) 8/23/2011 8:06:32 PM

>
>
> "Ashley Berg"  wrote in message 
> news:7e751dd7-f940-4246-bb73-a68fad00140d@bl1g2000vbb.googlegroups.com...
>
> Is there any way to calculate the area of a latitude-longitude
> quadrangle in IDL, or some formula I could use?
> MATLAB can (using areaquad from the Mapping Toolbox, which can return
> surface area in km^2 of a lat/lon box covering a part of Earth) but I
> do not have access to MATLAB.

actual surface area would be impossible, but just integrate the surface of a 
sphere and that could get you close enough.

cheers,
bob 

0
Reply noemail8476 (227) 8/23/2011 8:37:29 PM

On Aug 24, 4:52=A0am, Ashley Berg <ashley.b...@gmail.com> wrote:
> Is there any way to calculate the area of a latitude-longitude
> quadrangle in IDL, or some formula I could use?
> MATLAB can (using areaquad from the Mapping Toolbox, which can return
> surface area in km^2 of a lat/lon box covering a part of Earth) but I
> do not have access to MATLAB.

When I had to do something similar in Excel (don't ask!) I broke it up
into two triangles, found the internal angles (google Aviation
Formulas) and used Girard's theorem to find the area of each triangle
and added them together.

Max
0
Reply maxjpeck (28) 8/24/2011 7:54:59 AM
comp.lang.idl-pvwave 11030 articles. 11 followers. Post

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