Mapping the Shadows of New York City | Hacker News Reader

Mapping the Shadows of New York City

nytimes.com

129 pointsbaron81629 comments

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 (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

Using an extremely fast tool built by coworkers.

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.

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/

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

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

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."

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

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.

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.

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.

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.

Probably not. You can download the footprints of the buildings here:

https://data.cityofnewyork.us/browse?q=buildings&provenance=...

Other uses of this data:

https://nycopendata.tumblr.com/post/156085577820/one-dataset...

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!

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.

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.

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.

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

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

I have no idea :/

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...

"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.

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 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.

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?

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.

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

> it's too big (and dark in many places) for me.

I don't know about "too big" - that's pretty subjective - but it's plenty bright right now. Summer sun means it's hot and sunny, and will probably be that way most places you live - unless you happen to live in Midtown or Fidi, you'll be walking in the sun every day.

And remember, just because you're not in direct sunlight doesn't mean it's dark - most things around you will reflect light, especially the windows on buildings.

Apartments, however, are a much bigger toss-up. I've lived in places where most of our windows faced the sun (not particularly fun in the summer), and I've lived in basement/garden apartments where even when the sun did peek over the neighboring rooftop to strike our windowsill, the trees above us filtered most of it out.

One thing to remember is that this maps direct sunlight. Skyscrapers are decently reflective, and outside the absolute darkest blocks mentioned you can expect a fair bit of diffuse lighting.

Another is that New York State is just pretty dim and cloudy to begin with. The clouds can actually be nice, since they distribute light a bit better, but life in NY involves getting used to some awfully dark winters regardless.

> Don't think I could live there, I like sunshine

I live there. My Brooklyn apartment gets ample sunlight year round. Most people don't live in these hugely sun-starved areas, they're mostly offices. That said, it can be brutal in the winter: get up, it's light out, go to work in the dark on the subway, get to work in your fluorescent-lit midtown office building where you've been fighting for a window seat for 2 years because it makes you miserable to go a full day without any sunlight, stand on a street corner for 15 minutes during your lunch break just to see the sun that day, sun goes down at 4 PM and it's dark till the next morning. Nice.

That said, this is only for a month or two during the winter. My biggest problem living in NYC is, by far, noise pollution. It's next to impossible to find a place that's well and truly quiet, and I desperately need it from time to time.

> Can you build higher?

The current crop of large skyscrapers are facing severe difficulties[1] due to a slowdown in price increases, likely due to a slowdown in wealthy foreigners viewing Manhattan high-rises as an investment[2].

> I wonder what NYC will look like in 200 years

Depends how the transit situation and global warming situation goes (i.e. assuming NYC is not mostly underwater or destroyed by hurricanes). The first elevated rail line (predating all the subways and highways) in NYC opened about 150 years ago. A New Yorker 200 years ago surely couldn't have imagined the MTA subway network nor Robert Moses' car-oriented sprawl. Similarly, it's tough to imagine the city in 200 years, but I have some guesses for 100 years...

Infill will continue, and neighborhoods along subway lines will creep upward vertically, as higher and higher buildings pop up in further out neighborhoods -- this is how cities tend to grow, organically, gradually, one step at a time. My neighborhood, Bedford-Stuyvesant, is mostly 3-4 story brownstones, but I've seen a number of 7-8 story buildings appear over the last year. 1 story garages or empty lots in the neighborhood are also quickly being replaced with 3-4 story brownstone/rowhouses. If subway capacity (and demand) exists, the buildings will continue creeping up.

Beyond that, transit creates neighborhoods. The hardest part of transit, at least historically, has been right-of-way. Once Moses' network of highways outlive their lifespans and must be demolished (I give it less than 50 years, these highways weren't build to last[3]), it should be straightforward to convert them to at-grade train lines that integrate with the existing subway network. This will open up vast areas of Queens and perhaps even Long Island for higher density development (assuming the zoning laws can get their shit figured out regarding density/parking requirements before that happens). In terms of working locations, I fully expect Industry City and Downtown Brooklyn and Long Island City to become more important as destinations instead of the traditional Manhattan high-rise office.

Manhattan? It'll probably get some fancy new buildings here and there, but I imagine in 100 years it'll still look much the same. Zoning codes make it almost impossible to build taller/better than what's already there, in many cases[4], and these things are hard to change, because often the stakeholders in the old buildings are also the ones with a lot of political clout...

[1]: https://ny.curbed.com/2017/1/4/14157208/manhattan-real-estat...

[2]: https://www.nytimes.com/2015/02/08/nyregion/stream-of-foreig...

[3]: http://www.brooklynpaper.com/stories/32/19/32_19_mm_bqe_meet...

[4]: https://www.nytimes.com/interactive/2016/05/19/upshot/forty-...

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.

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

Awesome work!

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