* Torsten Dreyer -- Monday 11 February 2008: > You might also take weather phenomena into account. When there is > something like FG (fog) [...] There might be something like blown > sand [...]
True, but I'm mostly interested in reconstructing visibilities >10km, so I want to try to estimate values based on known visibilities in that range. Values below are only interesting for curve fitting, and there the few sand storms will only be noise. * LeeE -- Monday 11 February 2008: > I think I'd suspect the 110 miles figure (if that's a ground level > value) as well, not only because that's a lot of atmosphere to see > through but also because of curvature. According to google searches the 110 are realistic for the East coast (as a maximum), while visibilities in the West coast of the USA are much lower. But that should already be contained in the humidity. (Kind of, as we should really look at size and concentration of any particles. But humidity is all we have.) > I tried a quick Google to see if I could find any rules/formulae for > visibility due to atmospheric conditions but didn't hit anything. There are several hits that confirm the correlation of rel. humidity and visibility. There's even a paper for the airport in Tokyo that explores the relation and makes predictions based on that. But only for up to 4000 m, which can probably not be extrapolated. > It'll be interesting if you can come up with rules or a formulae > from your analysis of a large set of METAR data. The data set is ~100.000 entries, but while the method should be appropriate, my first graph didn't look promising. The rel. humidity calculation is relative simple in fgfs (and my test), and I might have to re-think that. That's why it took longer than my promised "later today". :-) (Also I've had other stuff on my list. But I'll revisit that topic.) m. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
