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[greybeard]

Hi guys!

Fiddling lately with maps environmental parameters, I wonder what exactly means DECLIN and how to compute it.

So far, I thought it was LATITUDE, but why calling it DECLIN? Then, I continue finding odd figures, like 5 for Nomonhan or 70 for winter map of Kurland. Both should be about 50, if latitudes! Summer map of Kurland bears a value of 54! Can't be all errors, I think.

Anyone knows?

[SAS~Malone]

DECLIN = declination angle of the sun.
changes with season/time of year.
nothing to do with latitudes.

[greybeard]

DECLIN = declination angle of the sun.

Thank you so much!

EDIT: as such (declination angle of the sun), shouldn't be more than 23°; so why all those 40-50-70° set in maps' load.ini? Are they wrong?

[greybeard]

I think I got it.

Must be the complement to 90° of elevation angle (altitude) of the sun, that's to say "Zenith" in following image:



this way, for instance, DECLIN figures for Kurland winter would be 80° and for summer 49°.

[Uzin]

DECLIN = declination angle of the sun.
changes with season/time of year.
nothing to do with latitudes.

As a mapmaker, I say thanks, greybeard.
So we have:

DECLIN = 90 - LATITUDE

[Whiskey_Sierra_972]

I used the latitude value in my MAPMODS and got good working maps daylight and sun zeniths....remember that originally the game don't allow to use negative value so the definidion LATITUDE isn't correct , I believe that the game DECLIN is the only positive value of the latitude....

[greybeard]

So we have:

DECLIN = 90 - LATITUDE

No. Exact formula is:

DECLIN = 90 - ELEVATION

where ELEVATION is maximum altitude in degree of the sun above the horizontal (please watch previous picture where Altitude = alpha; DECLIN is the angle phi=90-alpha, there named Zenith).

You may use following site to perform calculation:

Sun calculator

here follows an example:









as a consequence:

DECLIN = 90 - 65 = 25

No problem with negative values! Since they can't be!

------------------------------------------------
EDIT (27 February 2019):

Correction factor (see Reply #22) 0.75. As a consequence, ultimate formula in previous example is:

DECLIN = 90 - 65 = 25 * 0.75 ≈ 19

[Whiskey_Sierra_972]

Have you test value for near equator location and near north pole with your method in game?

Can you post some screens of the sun position at 06:00 , 12:00 and 18:00?

[Uzin]

I hope this thread will be done sticky. 

[Epervier]

I hope this thread will be done sticky.

Done ! 

[greybeard]

Have you test value for near equator location and near north pole with your method in game?

Nope. Testing is still in progress.

So far I notice only a delay in sunrise and an advance in sunset in respect of reality (I mean actual values taken from same site linked above). I guess this is due to IL2 world being flat, as sketched in following picture.

[SAS~Malone]

yes, i believe Oleg Maddox is a member of the Flat Earth Society... (jk)

editor note: please note, since we stickied this topic now, i've taken the liberty of editing the thread title to be a little more descriptive....