r.sun: wrong sign in equation of time

[tomhuld]

Bug report ticket #2876 by fabriziosossan reported a problem with the equation of time in r.sun, whereby the calculation of the solar time from the clock (civil) time is wrong. The problem was fixed with a patch for GRASS 6, but as far as I know there the fix was not applied to GRASS 7.

I would like to suggest the following patch for r.sun/main.c. Since this is my first patch for GRASS, apologies if I'm doing it worng.

--- main.c (revision 67790) +++ main.c (working copy) @@ -1766,7 +1766,7 @@

• "local clock time". */

dayRad = 2. * M_PI * day / 365.25; locTimeOffset =

• -0.128 * sin(dayRad - 0.04887) - 0.165 * sin(2 * dayRad +

+ +0.128 * sin(dayRad - 0.04887) + 0.165 * sin(2 * dayRad +

0.34383);

/* Time offset due to timezone as input by user */