Re: ski slope lighting (fwd)

["Hoek" <hosek@skiareal...>]

Děkuji za Vaši snahu a za získané informace.
Bohužel naše názory na potřebu osvětlení sjezdovky se diametrálně odlišují
a pro nás jsou Vaše závěry naprosto nepřijatelné. Nevím kde se stala chyba a
zda oba mluvíme o jedné věci (osvětlená sjezdovka pro sjezdové lyžování,
norma platná pro osvětlení sportoviš v ČR, atd.), ale lyžovat na takto
osvětlené sjezdovce je nemožné.

Děkuji

Michal Hošek
hosek@skiareal...



----- Původní zpráva -----
Od: "Jan Hollan" <jhollan@amper....muni.cz>
Komu: <hosek@skiareal...>
Odesláno: 11. října 2002 17:42
Předmět: Re: ski slope lighting (fwd)


> Vazeny pane Hosku,
>
> asi nejvetsi expertka na osvetlovani sportovist, pani Nancy Clanton, mi
> konecne odpovedela. Osvetleni, ktere dle vyzkumu je dostatecne silne,
> samozrejme jen pri dokonale kvalite, tj. optimalnim smerovani, je jeste o
> rad slabsi nez limit, ktery jsem navrhl jako horni hranici ja. Tedy ne tri
> luxy nebo dokonce pet luxu, ale jen tri desetiny luxu.
>
> Stredni jas sjezdovky by tedy bylo mozne limitovat pozadavkem, ze nesmi
> prekrocit desetinu kandely na metr ctverecni. Aby nebylo nutne spekulovat
> o tom, jak ktery snih rozptyluje svetlo, jako zaver sve EIA bych doporucil
> stredni osvetlenost sjezdovky pul luxu, s minimy ne nizsimi nez je
> desetina luxu a maximy ne pres dva luxy.  To vse samozrejme pri vylouceni
> prime viditelnosti svitidel pri jizde dolu, diva-li se lyzar/ka pred sebe
> na cestu.
>
> Samozrejme trvam na pozadavku, ze stredni jas nesmi prekrocit onu 1 cd/m2
> -- bezpecnost lyzaru rozhodne nevyzaduje vice. Kdybyste chteli osvetlovat
> az na samu tuto hranici, pak stredni osvetlenost sjezdovky nesmi v zadnem
> pripade prekrocit 4.9 luxu.
>
> Doposud jste se mi neozval s fotometrickymi udaji o svitidlech, ktera byla
> v puvodnim projektu. Velmi pochybuji, ze jsou takova, jako doporucuje pani
> Clanton...
>
> Jeji stanovisko mohu prelozit do cestiny, pokud by bylo treba.
>
> Ozvete se mi prosim, staci telefonicky, na hvezdarnu mam 5 41 32 12 87,
>  dom 5 43 23 90 96, v utery a stredu budu ale prednaset na 21. kursu
> osvetlovaci techniky v Moravce.
>
> zdravi Jenik Hollan
>
> ---------- Forwarded message ----------
> Date: Thu, 10 Oct 2002 20:26:11 -0600
> From: Nancy Clanton <nancy@clantonassociates...>
> To: Jan Hollan <jhollan@amper....muni.cz>
> Subject: Re: ski slope lighting
>
> Sorry for the delay in my response. It has been an extremely busy month,
and I
> am just now getting to my "fun" emails.
>
> You are very correct in limiting the brightness to 1 cd/m2. We have run
> experiments on ski slope lighting and have produced lighting to about 3
times
> full moonlight, or around 0.3 lux. In Colorado, people readily ski under
full
> moonlight, and so we tried to duplicate these results. The key to great
ski
> slope lighting is not the amount of light, but how you light it. High
amounts
> of "flat" lighting similar to a cloudy day can result in disastrous skiing
> conditions. But, if the lighting highlights the terrain roughness with
> shadows, skiers can easily see even under low lighting conditions.
>
> Our experiment involved many expert skiers, skiing at high speeds. We
asked
> them when the lighting was too low for them to feel safe. It was below 0.3
> lux. We also employed a vision scientist, and he said that there was
plenty of
> light to ski and that we could even go lower.
>
> So, the important thing, is to install uni-directional lighting. Do not
aim
> the lights uphill at all. With lighting that is "full cut-off"
asymmetrical
> luminaires, aimed downhill, and the lens parallel with the slope, you
should
> have great results.
> Good luck,
> Nancy Clanton
>
> Jan Hollan wrote:
>
> > Dear Nancy Clanton,
> >
> > David Crawford recommended me to ask you, when I looked around (at the
> > European DarkSky symposium in Lucerne) to find somebody who has an
> > experience with lighting of slopes for downhill skiing. He was sure you
> > have.
> >
> > A National Park in northern Czechia demanded an Environmental Impact
> > Assessment concerning a project to light one slope there, and I am in
fact
> > the only Czech expert in environmental consequences of outdoor lighting.
> >
> > A colleague from Catalonia said me that ski lighting will be forbidden
> > there. This is of course the most environment-friendly possibility.
> > However, it would demand strong arguments and might be very unpopular in
> > Czechia -- there are some lit slopes already, even if not in national
> > parks. I'd prefer some compromise solution to show, that light pollution
> > prevention does not imply an end to the nowadays way of life, but rather
> > brings a new quality to it.
> >
> > Therefore my draft recommendation has been to use decent amount of
light,
> > giving the snow the luminance around the top limit of the values
> > recommended for roads, namely not exceeding 1 cd/m2. Even such a
luminance
> > of a long slope would illuminate substantially a vast area on the
opposite
> > side of the valley.  Some five lux of horizontal illuminance should give
> > that 1 cd/m2 perhaps, even with the least white snow. The skiers
> > themselves would be illuminated more on the average, thanks to the light
> > from the snow; even in places with no direct vertical illumination they
> > should be lit by some two lux. I suppose that such values should do, if
> > the light from the luminaires above 75 degrees from the slope will be
kept
> > to minimum (i.e., with more than FCO demands).
> >
> > The project mentioned however an average horizontal illuminance of 20
lux
> > for each evening, with a possibility of 100 lux for occasional
> > competitions. 20 lux is mentioned in some technical standard for skiing.
> > If I compare it with the recommended 4 lux for areas with many
pedestrians
> > and cyclists (cyclists are going more often in opposite directions),
> > it seems to be an overkill to me. The slope has an only simple lift, so
> > the traffic on the slope will be kept low.
> >
> > Another argument for not so large light levels is, that the surrounding
> > paths won't be lit -- the lift itself (being divided from the downhill
> > slope by a strip of forest) and the paths (some are in a dense forest)
to
> > the other parts of that skiing resort. With too much light on the slope,
a
> > proper adaptation to move safely on those paths would demand too long
time
> > to happen in reality. In view of this fact, perhaps 2 lux horiz. illum.
on
> > the slope would be better than five.
> >
> > The owner argues however that some previous experience showed, that even
> > 20 lx is not enough, that there have been some collisions. My answer was
> > they have been quite possibly due to glare. The more dangerous as the
> > skiers can carry glasses with snow or drops on them. Low glare should be
> > more productive than lots of light.
> >
> > I'd like to adhere to the 1 cd/m2 limit, as we plan to put it into the
> > Czech regulations, for all cases where safety standards don't demand
more.
> >
> > I would not say that 20 lx for skiing is a safety standard. If it would
> > be, than the skiing on slopes with no artificial lighting should be
> > abandoned even before sunset on the most heavily overcast days (say,
with
> > just some man-made snow on the slope and a dark landscape elsewhere),
but
> > all lifts operate till sunset in December and January. The more because
> > the omnidirectional light from an overcast sky hinders recognition of
any
> > shapes on the slope, unlike sunlight or light from luminaires.
> >
> > But, your experience and opinion would be most authoritative for me. If
> > you would agree with the low light levels, than that skiing slope could
> > become a landmark in sustainable sports lighting. Otherwise I would
rather
> > recommend to avoid such a disturbance amidst a national park (even if
> > there is a town in its centre).
> >
> > sorry for a long letter,
> >  your sincerely
> >  Jenik Hollan, IDA Czech Republic
>
>