[GRASS-dev] [GRASS GIS] #3052: Watts to MegaJoules/Day conversion issue

[GRASS GIS]

#3052: Watts to MegaJoules/Day conversion issue
--------------------------+---------------------------------
  Reporter:  cholmes      |      Owner:  grass-dev@…
      Type:  defect       |     Status:  reopened
  Priority:  normal       |  Milestone:  7.0.5
 Component:  Imagery      |    Version:  svn-releasebranch70
Resolution:               |   Keywords:  i.evapo.mh
       CPU:  Unspecified  |   Platform:  All
--------------------------+---------------------------------
Changes (by neteler):

 * cc: ychemin (added)
 * status:  closed => reopened
 * version:  unspecified => svn-releasebranch70
 * resolution:  fixed =>


Old description:

> I think I may have found an error in a few files from the grass-ci repo.
>
> A few files:
>
> https://github.com/GRASS-GIS/grass-
> ci/blob/f1a15d967611006e920b8dc2f191391e44392019/imagery/i.evapo.mh/mh_eto.c#L15
> https://github.com/GRASS-GIS/grass-
> ci/blob/f1a15d967611006e920b8dc2f191391e44392019/imagery/i.evapo.mh/mh_original.c#L14
> https://github.com/GRASS-GIS/grass-
> ci/blob/f1a15d967611006e920b8dc2f191391e44392019/imagery/i.evapo.mh/mh_samani.c#L14
>
> contain a line like:
>

> {{{
> ra = ra * (84600.0 * 1000.0);   /*convert W -> MJ/d */
> }}}
>

> I'm guessing the magic constant 84600 is intended to be the number of
> seconds in a day, which is actually 86400. Also, Watts * Seconds gives
> Joules. If you intend to get MegaJoules, you must divide by 1000, not
> multiply (but maybe the comment is just wrong, and you wanted
> milliJoules?).

New description:

 I think I may have found an error in a few files from the grass-ci repo.

 A few files:

  * https://github.com/GRASS-GIS/grass-
 ci/blob/f1a15d967611006e920b8dc2f191391e44392019/imagery/i.evapo.mh/mh_eto.c#L15
  * https://github.com/GRASS-GIS/grass-
 ci/blob/f1a15d967611006e920b8dc2f191391e44392019/imagery/i.evapo.mh/mh_original.c#L14
 https://github.com/GRASS-GIS/grass-
 ci/blob/f1a15d967611006e920b8dc2f191391e44392019/imagery/i.evapo.mh/mh_samani.c#L14

 contain a line like:


 {{{
 ra = ra * (84600.0 * 1000.0);   /*convert W -> MJ/d */
 }}}


 I'm guessing the magic constant 84600 is intended to be the number of
 seconds in a day, which is actually 86400. Also, Watts * Seconds gives
 Joules. If you intend to get MegaJoules, you must divide by 1000, not
 multiply (but maybe the comment is just wrong, and you wanted
 milliJoules?).

--

Comment:

 Reopening for the issue: 84600 should be 86400 (?)

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Ticket URL: <https://trac.osgeo.org/grass/ticket/3052#comment:5>
GRASS GIS <https://grass.osgeo.org>