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 */

[neteler]

Replying to 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,

So far the proposed patch has not been applied. Should it be? From the discussion in ticket #2876 it is not clear to me.

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.

Ideally please submit the diff as an attachment by (in this case) running

# from main source code directory
svn diff raster/r.sun/ > r_sun.diff

(For now, I have reformatted your comment here by protecting it with curly braces.) Should your change be submitted in addition to the patch proposed in ticket #2876 or exclusively your change?

[neteler]

Thanks for the patch, applied in r68254 (relbranch70) and r68255 (trunk).

Compare also the equivalent alternative GRASS GIS 7 fix suggested in #2876 (commented on in cited email in ​​https://lists.osgeo.org/pipermail/grass-dev/2016-April/079789.html).

Closing.