[OpenLayers-Users] Square miles from Square degrees?

[cmose]

Hmnn after giving this a go I seem to be getting wildly inaccurate results,
at least I believe I am. For instance, I used a polygon over an area I know
to be roughly 400k square kilometers. Using the getArea on the polygon
(after converting points to sphericalmercator) I'm getting a result of
748,912,714 sq. km...

Anyone have any pointers or ideas of where I might be going wrong here?
Thanks!

Josh Livni-4 wrote:
> 
> 
> I've not played with the getArea function, but since area calculations 
> in the base coordinate system (geographic/dec. degrees, or however it's 
> best described) make no sense, I think the only way you can do this with 
> the current codebase would be to use the forwardMercator equations found 
> in OpenLayers.Layer.SphericalMercator.
> 
> After reprojecting your geometry to spherical-mercator, an area 
> calculation would make more sense, and be in meters (though still be off 
> by I'm guessing a few percent, depending on the size of your geometry 
> and it's location).
> 
> I think the trunk and next version of OL may include additional methods 
> of getting to use SphericalMercator, and perhaps even other projections, 
> but I'm not too clued in on the details.
> 
> -Josh
> 
> 
> cmose wrote:
>> Hopefully I'm not making a fool of myself but my assumption is that the
>> getArea function on Geometry/subclasses returns square degrees (that
>> seems
>> to be the case to my eye). How exactly would I go about calculating
>> square
>> miles from this or is that even possible? If not, how do I go about
>> calculating the square miles contained in a shape drawn on the map?
>>
>> Thanks!
>>   
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