Wikipedia:Reference desk/Archives/Miscellaneous/2019 July 13

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July 13

How do they measure ski trails?

On Heavenly Mountain Resort's website--and on the article's infobox--it is reported that the resort's longest run, Olympic Downhill, stretches over a distance of 5.5 miles (8.9 km). However, when I measure on Google Earth, roughly following the path from the East Peak summit down to the base, I get a distance of 1.8 miles (2.9 km), which follows the slope and counts the Z-axis, and is therefore the accurate traveled distance. (Even if Google gave a horizontal distance, then it would be maximum 2.5 mi (4 km) at the 100% slope, 45°).

So they say 5.5 miles, I get 1.8 miles. I'm at a loss here. The only simple explanation I have is that they calculate the actual wavy track taken by an average skier including every twist and parallel turn, but it seems off that this would add up to triple the length. — Define Real (talk) 13:29, 13 July 2019 (UTC)

Sounds related to the coastline paradox. Note that if it has up and down hills on the way down, that would increase length over a steady slope. That, combined with side-to-side variation, might get you there. And they might be exaggerating a bit, too. SinisterLefty (talk) 13:44, 13 July 2019 (UTC)

Right, I'm thinking it's related to the fractal problem. I hope to get a more definitive answer but is the most likely scenario, and if that's the case then it seems quite arbitrary and misleading, I wonder if all ski runs are calculated this way. Thanks for your help. — Define Real (talk) 15:21, 13 July 2019 (UTC)

In Europe, there is the Verified Length of Runs scheme "ensuring greater transparency and customer-friendliness in the winter sports industry... for the first time ski areas have the chance to have their actual length of runs verified by a credible and independent authority". The same page reports that 21% of ski run measurements in the Alps have a divergence from reality of between 50% and 100%, although none exceeded 100%. Alansplodge (talk) 14:39, 14 July 2019 (UTC)

Also a report that Resorts Remeasure Piste Lengths (2013) after a German cartographer "measured the lengths down the middle of the pistes, following the twists and turns, using a digital mapping system" and compared this to published guidebook data. He found that "the Four Valleys resort, Switzerland: Schrahe measured 164 kms and the resort claims 412 kms. This is a 151% discrepancy or 248 kilometers of non-existent piste". Alansplodge (talk) 14:57, 14 July 2019 (UTC)

Though I am no more familiar with skiing conventions than any other non-skier who has occasionally watched Winter Olympics broadcasts, I am aware that different marked-out pistes are rated according to relative difficulty, so I wonder if some pistes may have two or more differently marked out 'courses' (not necessarily used concurrently) on the same 'snowscape' that may be legitimately measured multiple times, once for each different course? I also wonder how 'off-piste' areas with no set routes might figure in to the measurements. {The poster formerly known as 87.81.230.195} 2.122.177.55 (talk) 20:07, 14 July 2019 (UTC)

Fascinating stuff. I understand why they calculate the actual skiing route with the twists and turns (though they should make that clear somehow), but it seems they take the worst case scenario of a skier making the widest, slowest possible turns. Quite misleading as I doubt most skiers would cover 300% of the run's actual length... the reports cited above show a substantial discrepancy. I like the notion of an independent verification scheme. Thanks all for your informative replies. — Define Real (talk) 21:56, 14 July 2019 (UTC)