
Mapping the Shadows of New York City - baron816
http://www.nytimes.com/interactive/2016/12/21/upshot/Mapping-the-Shadows-of-New-York-City.html?hp&action=click&pgtype=Homepage&clickSource=story-heading&module=second-column-region&region=top-news&WT.nav=top-news
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solarspeed
Huh, just yesterday I tried something like this, but lacking elevation data
for NY I settled for most of Europe:
[https://i.imgur.com/b7h3ulR.jpg](https://i.imgur.com/b7h3ulR.jpg) (I
downscaled the resulting 198'000x126'000 image to 4'950x3'150.)

And some more high resolution ones, e.g. Salt Lake City
[https://i.imgur.com/R352z2l.jpg](https://i.imgur.com/R352z2l.jpg)

Using an extremely fast tool built by coworkers.

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Shengbo
It's really cool to see the natural borders of countries in much higher
contrast than a regular elevation map. Especially the Alps walling off
Northern-Italy from the rest of the continent and the way the Carpathian basin
is surrounded by terrain that made it hard to invade. Makes sense that it was
such a heavily contested area around the 9th century.

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shrx
Pretty awesome visualization. Does anyone know if the authors published a
paper on the "shadow computation that is 10 to 15 times faster than older
methods"? I couldn't find it on their websites [1-3].

[1] [https://vgc.poly.edu/~fmiranda/](https://vgc.poly.edu/~fmiranda/)

[2] [https://vgc.poly.edu/~csilva/](https://vgc.poly.edu/~csilva/)

[3] [http://www.harishd.com/home/](http://www.harishd.com/home/)

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theoh
It sounds like a way to take larger simulation steps by linearising the
movement of projected points on shadow outlines. I'm guessing a bit, but the
idea of figuring out how to take larger steps is an established trick for
speeding up simulations (e.g. the Siggraph paper "Large Steps in Cloth
Simulation")

"Instead of explicitly tracking the movement of the sun, which is how shadow
accumulation is usually measured, the researchers are tracking the movement of
the shadows. Using the key insight that shadows move linearly within a short
time range, they designed an efficient algorithm that performs an order of
magnitude faster than those used in existing approaches. “This also allows
users to interactively compute and explore shadows over different time ranges
and allows them to quickly test multiple scenarios,” said Doraiswamy."

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pavement
It'd be interesting to see a composite of reflected sunlight included around
the builings with highly reflective exteriors.

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Bartweiss
This strikes me as a definite perk of the glass-and-steel skyscraper design.
Older brick and stone designs seem to waste a lot more light, especially as
they get dirty and lose albedo.

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twobyfour
Brick and stone buildings have mostly been kept clean the last 15 years or so,
and they don't darken as quickly as they did in the 20th C when both
transportation and industry produced far more soot.

That said, I've seen buildings that were nearly black with 100 years of
accumulated soot at the end of the 1980s undergo deep cleaning (sandblasting)
in the 90's and come out off-white. It's pretty remarkable.

25 years later, those same buildings are now almost exactly the same color
they were immediately after the cleaning, without any further maintenance.

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Bartweiss
It is a pretty stunning difference. Honestly, I think I'm mostly thinking of a
handful of black stone buildings (famously, American Radiator) and buildings
which haven't been cleaned since the '70s or '80s.

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QuelqueChose
Is this the first time somebody's constructed an interactive map of every
single building in the greater NYC metropolitan area? It's really the part of
the article that I find most impressive.

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pokemongoaway
Seems like a good opportunity to sell data to those in real estate. For
example, why would someone pay the same for two different apartments on the
same floor when one gets direct sunlight door 30% of the day, and the other
gets none!

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pavel_lishin
For that matter, you can market _both_ of those as advantages.

Apt A: "Save hundreds on air-conditioning in the summer - this apartment never
feels the full brunt of the scorching sun!"

Apt B: "Wake up every morning to a New York sunrise - the best way to beat
those winter blues."

Just gotta know what the tenant is looking for.

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rdnt02
Almost always you want Apt B. Bright sunlight can be controlled with
electronic transition glass, curtains and other methods. You can't reproduce
sunlight in your apartment.

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yathern
I find it surprising you mentioned electronic transition glass - I had thought
it's not used pretty much anywhere as of yet, and prohibitively expensive.

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pavel_lishin
The only place (I think?) I've seen it was on the Boeing Dreamliner.

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malnourish
Didn't some Maybachs have it? Or is that a different kind of glass?

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pavel_lishin
I have no idea :/

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baron816
New York NIMBYs often refer to shadows when trying block the construction of a
new building. But as covered in shadows as New York is, it doesn't have a
shadow problem. It has an affordability problem. Lots of people are willing to
spend crazy amounts of money there (many of whom could live anywhere in the
world) because it's still an amazing place to live. More people would love to
live there, but there is, of course, a shortage of affordable housing...

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key8700
"It is said that the sun rises in the east and sets in the west. But at New
York’s latitude, that’s not quite the case. On the summer solstice, the sun
rises in the northeast and sets in the northwest, while on the winter
solstice, the angle changes and the sun rises in the southeast and sets in the
southwest. "

I thought the sun's path was always south of due East-West for locations north
of the Tropic of Cancer at all times of the year.

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rz2k
Above the tropic of cancer, the sun is south of you at noon even in the
summer, but rises and sets a little in the north because the earth is more
spherical than cylindrical.

I think [http://www.suncalc.org](http://www.suncalc.org) is a useful site for
seeing where the sun will be at different times of the year. Zoom out the map,
then move the dynamic icon north and south in June and December.

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coldcode
Don't think I could live there, I like sunshine. Some people love living in
the city because of all the amazing stuff you can do there, but it's too big
(and dark in many places) for me. I wonder what NYC will look like in 200
years. Can you build higher?

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NathanKP
As much as I like the interactive map the truth is it makes things look way
more shadowed than they actually are because its showing the averages of
shadows from all time of the year and all times of the day. The reality is
that most of the streets have a shady side and sunny side at all times of the
year. It's shady on one side of the street in the morning and shady on the
other side in the afternoon.

This is actually great because you can choose the side of the street to walk
on. If you are too hot in the summer you can go walk on the shaded side, or if
you are too chilled in the spring/fall/winter you can walk on the sunny side.
During the summer it is actually very nice to have a long stretch of tall
buildings where you can cool off by walking on the shady side of the street.

It's kind of like enjoying walking down a street that is shaded by a lot of
trees, although sadly the buildings don't absorb as much heat as the trees do,
and in some cases glass buildings actually seem to reflect the heat harshly.

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hammock
Good point. They could have projected only the shadows before noon, or
separate morning/afternoon shadows with a toggle.

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amichal
Very cool. The explaination of "shadow accumulation" would have been a bit
closer to reality if they had used hours in their example. shadows don't move
anywhere near that far in 1 minute.

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hammock
Some cool accompanying photos. I also enjoyed seeing the buildings' shadows
projected onto the Hudson River

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piyush_soni
Awesome work!

