[esp-r] defining general polygon obstructions

[Lomanowski, Bartosz]

A question about general polygon obstructions (type 'obsp'): 
 
>From reading the help info I understand that such a polygon must have flat surfaces. Are there any other constraints in defining such an obstruction? Is there a particular order for defining the vertices such as the anti-clockwise rule? Does it matter whether vertices 1-2-3-4 make up the bottom or the top surface?  
 
I ran a quick comparison of two different definitions of the same obstruction ( see attached jpeg ). There were differences on the order of 0.05 in the insolation and shading factors. Which of these is deemed correct?
 
Thanks,
Bart
 
NRCan, Canada
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