How It's Made
Drawn From the Survey, Checked Against the Sign
The whole method is on this page for anyone who wants to check it: where each run comes from, how its length and drop are measured, how our vertical is counted, and every mountain where our figure and the resort's part ways.
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Where the mountain comes from
Each mountain is drawn from OpenStreetMap, the map its volunteers survey: every downhill piste with its name, difficulty and grooming, every lift but the goods lifts, the stations, the peaks with their heights, and the woods, rock, glacier, water, roads and buildings round them. Nordic, touring and sledding trails are drawn faint and never counted.
How a run is measured
A run's length is measured along the line it was mapped, on the WGS84 ellipsoid, the same surface a GPS uses. The ways of one name and one difficulty that meet end to start are one run, and a run with branches keeps its longest line. An unnamed way counts as a run at 300 metres or more; shorter, it's a connector, drawn and not counted.
Its drop is the height at the top less the height at the foot, read from the AWS Terrain Tiles at zoom 14 where the mountain is small enough, zoom 13 otherwise. That's about 7 metres to a pixel at zoom 14 and 14 at zoom 13, so a cornice or a cat track narrower than that is smoothed over. The steepest 100 metres is the steepest fall over any 100 metres along the run.
How the vertical is measured
Our vertical runs from the highest lift's top station to the lowest lift's bottom station, both read from the terrain at the lift's own end. Station placement in OpenStreetMap is the largest source of difference: a station mapped 20 metres down the slope moves the figure. A mountain that publishes from a hike-to summit, or from a village below its lowest lift, will differ from ours, and we print both numbers rather than choosing.
The receipts
We check our vertical against every mountain whose own page states one, within the larger of 5% and 60 metres, fixed before the first comparison and never loosened. A mountain outside it stays in the table with the reason, and the print carries both figures either way: a mountain that counts from a hike-to summit, or from a village below its lowest lift, comes out different from us, and the table says so rather than nudging our number toward theirs.
| Mountain | It publishes | We measure | Difference | Within the larger of 5% and 60 m? |
|---|---|---|---|---|
| Jackson Hole Mountain Resort | 4,139 ft | 4,072 ft | −20 m | Within |
| Big Sky Resort | 4,350 ft | 4,339 ft | −3 m | Within |
| Mammoth Mountain | 3,100 ft | 2,912 ft | −57 m | Within |
| Palisades Tahoe | 2,850 ft | 2,530 ft | −98 m | Outside: the resort counts to its 9,050 ft peak; we count to the highest lift station, Emigrant's top, which stands lower |
| Taos Ski Valley | 3,131 ft | 3,137 ft | +2 m | Within |
| Telluride Ski Resort | 3,790 ft | 3,748 ft | −13 m | Within |
| Sun Valley | 3,400 ft | 3,365 ft | −11 m | Within |
| Killington Resort | 3,050 ft | 3,129 ft | +24 m | Within |
| Lake Louise Ski Resort | 991 m | 3,070 ft | −55 m | Within |
| Niseko Grand Hirafu | 940 m | 919 m | −21 m | Within |
| Deer Valley Resort | 3,040 ft | 3,093 ft | +16 m | Within |
| Shiga Kogen | 1,000 m | 728 m | −272 m | Outside: the survey's one mountain in our sector runs from Hōsaka and Maruike north to Okushiga, topping out at Terakoya, 2,060 m; Yokoteyama and Kumanoyu, where the resort's 2,307 m top stands, are not in it, so our 728 m is the central and northern areas only |
| Ischgl | 1,495 m 1,377 to 2,872 m | 1,515 m | +20 m | Within |
| Madonna di Campiglio | 1,650 m 850 to 2,500 m | 1,701 m | +51 m | Within |
| Thredbo | 565 m 1,365 to 1,930 m | 672 m | +107 m | Outside: the resort's page states its heights as 1,365 to 1,930 m; the top of Karels T-Bar, the highest lift station in the survey, stands above 1,930 m, so our 672 m runs 107 m past the span it states |
How each style is drawn
Every style draws the same survey on the same ground; what changes is how the ground is shown.
- Relief casts the mountain's shadows from the terrain's heights, with the sun low in the south-east.
- Oblique tilts the terrain sixty degrees and shows it from the side its base village sits on, so a run behind a ridge is hidden where the ridge hides it.
- Trail Map draws the plan flat: the survey's woods as trees, its rock hatched, every run in its grade's colour beside its symbol.
- Survey draws contour lines from the terrain, every 10 metres where the tiles hold at zoom 14 and every 20 elsewhere, with the runs in ink over them.
- Contour draws the same contours alone, the heavier lines labelled with their height, and the runs over them.
- Watercolour lays two washes over each wood, rock and lake in the survey, the second a shade lighter, on a ground that turns a cool blue on every face the terrain shows pointing north.
- Linocut prints two colours from one block: the forest cut as solid masses, the runs cleared through the snow as channels.
- Gilt draws every run and lift in gold line on a dark ground, inside a gold keyline.
The large editions
Every picture of a print on this site opens into a large edition, 2,000 by 3,000 pixels, drawn from the same survey and the same seed as the small one, so the two are one picture at two sizes; a test checks that on every build. The large edition is fetched only when you open it. The print itself is drawn at 150 dpi or more: the 40 × 60 in canvas goes to the printer at 6,000 by 9,000 pixels.
Difficulty, in the mountain's own symbols
A North American mountain prints green circles, blue squares, black diamonds and double black diamonds. A European mountain prints blue, red and black, and a French one adds green for its easiest runs. A Japanese mountain prints green, red and black. A run the survey leaves unrated prints grey and is counted as unrated; we never guess a difficulty.
What we refuse
- A mountain with fewer than 12 mapped downhill runs. The studio shows the count, and a form to hear from us when the map clears 12. Anyone who skis the mountain can add its runs at openstreetmap.org.
- Any copy of a resort's own trail-map artwork. The drawing is ours, made from the survey.
- A figure the browser sends. The server measures every run again before it prints.