Hi list.
If I understand the theoretical background for r.sun, then, horizon maps are an option to speed up calculations. If this is true, this is not necessary when working in smaller regions (where memory and processing speed are simply enough).
In this case, r.sun's optional parameter "horizon_step" is only bound to an optionally defined horizon map. Wouldn't it make sense, then, to add another rule for this option, to warn a user that "horizon_step" serves for the "horizon_basename" option? Something similar like the error message in r.sun's main.c:
--%<---
607 }
608 else if (useHorizonData()) {
609 G_fatal_error(_("If you use the horizon option you must also set the 'horizonstep' parameter."));
610 }
-->%---
Thanks for any explanations/comments in advance, Nikos