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The geometry of the array is what is called "hexagonal lattice": vertices of 
equilateral triangles that tile the plane.
I suppose this has to do with minimizing of the shading of turbines by each 
other with various directions of
the winds. The orientation of the lattice is probably related to the 
prevailing wind directions in the area.

When sailing in the Baltic sea, I passed through several of these huge farms. They are very common there
near the Danish shores.

Alex.  
 
________________________________________
From: NavList@fer3.com [NavList@fer3.com] on behalf of Russell D. Sampson [NoReply_Sampson@fer3.com]
Sent: Saturday, January 7, 2023 1:00 PM
To: eremenko@math.purdue.edu
Subject: [NavList] Re: Wind turbines beyond the horizon

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Frank:

Very interesting problem.  One thing to consider is the geometry of the array. 
If the map is correct then the spacing is neither orthogonal (i.e., like 
ordinary graph paper) nor aligned with the cardinal points.  I am guessing 
this may have to do with meteorology (prevailing winds) and aerodynamics 
(downwind turbulence).

Russ

On Fri, Jan 6, 2023 at 3:32 PM Frank Reed 
> wrote:

I spotted this random photo (from a friend of a friend) today on Facebook, and 
I am borrowing it without credit mostly because I can't figure out where I 
found it originally! It's a beach shot looking east-southeast from Pagham, 
Bognor Regis on the southern coast of England. The photo captures long rows 
of giant wind turbines, miles away, in the Rampion offshore wind 
farm. This has relevance to navigation 
because there are various angular piloting problems that can be puzzled out 
here (*), and also because we have a textbook case of "masts" of fixed height 
dropping away in apparent height beyond the horizon. Does it make sense? That 
is, do the apparent angular heights beyond the horizon match our expectations 
from navigational formulae? I made a map based on one at the wind farm's 
website that may help. I haven't worked this out in detail. But it seems like 
an interesting puzzle, and, like I say, a textbook case of beyond the horizon 
angles.

Frank Reed
* There's a nice navigation trick here. If you look out there with your 
binoculars and see all the turbines in one of the farm's rows all stacked up 
on top of each other visually (like the left-hand group in the photo), then 
you've got a line of position running right along that row. Of course you 
have to make sure you count correctly and know just which row you're aligned 
with!

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