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When it rains it pours: NYC GIS data floodgates opened

Lately NYC agencies have started to step up the pace in producing an impressive amount of publicly accessible GIS (and other) data.  It’s a very good direction (and hopefully one that all agencies will soon follow).

This summer, the big news was that MapPLUTO was all of a sudden available for free.  And then ACRIS was opened up (not geospatial, but key to analyzing spatial patterns of property transactions).  And before that HPD had posted a large amount of housing data (albeit in a wacky XML format, but nonetheless it was a lot and it was freely available and it was being updated regularly).

But today there’s even more…

… Historical MapPLUTO!

The latest news – spotted by eagle eye GIS star Jessie Braden – is that historical versions of PLUTO and MapPLUTO are now freely available, going back to 2002.  Really great.

And City Planning included an important but bittersweet note at the historical download page: sweet because all of us who had to sign licenses to obtain PLUTO data are now absolved from the license restrictions, but bitter because there was no mention of the thousands of dollars each of us have had to spend unnecessarily over the years to obtain that data that is now online for free.  Sigh.  Here’s the note:

Note to Licensees:
DCP releases all licensees of PLUTO and MapPLUTO versions 02a through 12v2 from all license restrictions.

One thing to point out about the historical PLUTO data is to be careful if you’re hoping to compare and analyze parcels year to year. Our team at the CUNY Graduate Center tried that a few years ago, and it was painful. So many data inconsistencies and related issues. The best we were able to do was display historical land use patterns via the OASISnyc.net website (for example, look at the disappearance of industrial land use in Williamsburg from 2003 to 2010). I’d be glad to explain in more detail if anyone is interested.

Building footprint data too

Other good news for all of us who use the city’s GIS data is that it seems that building footprints are being updated on a more regular basis, and more attribute information is being added (hat tip to Pratt’s Fred Wolf for discovering it).  The latest building footprint data is dated September 2013, and includes new attributes such as building height and type, and includes a supplemental data set on “historic” buildings (ie., ones that have been demolished, with date of demolition).

Agency data web portals are a beautiful thing

Thankfully the NYC Dept of City Planning staff are continuing to maintain the Bytes of the Big Apple website, where the PLUTO data is available along with many other spatial and non-spatial planning-related data sets.  The Bytes pages provide essential metadata about each data set, easily accessible contact information, and context about the data sets.

All of that is missing from the city’s open data portal, which I think is a major failure with the city’s open data practices.  (Someone even commented on the buildings data set noted above, asking great questions about how the building heights were calculated, and about the source of these calculations – essential information that is too often missing from data sets available through the portal, though usually included when you download the data from the agencies directly.)

As long as the data portal doesn’t undermine invaluable agency websites like Bytes of the Big Apple, and more data keeps getting freed and accessible on these agency sites, that’s a great thing.  And hopefully more agencies will either continue to maintain their own online data repositories (such as the departments of Buildings, Finance, HPD, Health, and others) or launch new ones (such as MTA did a couple of years ago).

Happy holidays …

… and big kudos to the City Planning department for explicitly posting the historical PLUTO data sets!

NYC’s MapPLUTO is free!

Download away!  http://www.nyc.gov/html/dcp/html/bytes/applbyte.shtml

This essential corpus of public data is now (finally!) freely accessible.  According to the metadata:

Access Constraints: MapPLUTO is freely available to all New York City agencies and the public.

Thanks to:

  • Jessie Braden at Pratt Institute for pointing it out,
  • 596 Acres for pressing the FOIL case with the city (and a similar effort from Muck Rock),
  • The New York World for highlighting the irony of charging fees and licenses for this data,
  • the NYC Transparency Working Group for pressing the city on all things opendata,
  • anyone and everyone in city government who pressed for this change from the inside, and
  • thanks to everyone else who helped shine a light on this ongoing failure of the city’s open data efforts — that has now been turned around!

A Modest Victory regarding NYC Tax Parcel Data

After I blogged this morning about the frustrations of the City Planning Department’s restrictions on mapped tax parcel data, I learned that the foundation of their “MapPLUTO” product is now available for free online.

This is a partial – but very important – victory for anyone who has been impacted by the city’s burdensome fees and license restrictions associated with MapPLUTO.

The good news is that the Department of Finance has decided to post its “Digital Tax Map” in GIS format online for free download.  (Thanks to Colin Reilly for alerting me to the online data.)  Here’s the link: https://data.cityofnewyork.us/Property/Department-of-Finance-Digital-Tax-Map/smk3-tmxj

Start mapping real property data!

To some extent, this pulls the rug out from under City Planning’s efforts to restrict access to tax parcel data, enabling anyone now to analyze and map the spatial patterns of land use, real property tax assessment, ownership, and more across the five boroughs.  Here’s what you’ll need to do:

  1. Download the Digital Tax Map file from the city’s Open Data Portal (when you unzip this file, you’ll actually receive a collection of GIS shapefiles and data tables);
  2. Download the assessment roll file (also for free online).  The Finance Dept makes this available in Microsoft Access format.  You’ll want to download the separate files for “Tax Class 1” and “Tax Classes 2, 3, and 4”.  The “condensed” version of the file only has a limited number of fields, nowhere near what MapPLUTO has;
  3. Combine the two “Tax Class” downloads into a single file;
  4. Join this combined file with the “DTM_1212_Tax_Lot_Polygon” shapefile using a robust GIS package such as ArcGIS or QGIS; and
  5. Map away!

Not a total MapPLUTO replacement, though

The “Tax Class 1” and “Tax Classes 2, 3, and 4” assessment roll files contain most, though not all, of what the City Planning Department packages as part of its MapPLUTO product.  Some missing items include:

  • Detailed parcel-level zoning characteristics;
  • Floor Area Ratio (FAR), a critical factor in making parcel-specific land use decisions;
  • Land use characteristics (though this can be calculated based on the assessment roll’s “building class” codes and a formula published by City Planning);
  • The various tract and district IDs for each parcel (but this can be calculated using GIS);
  • Parcel-specific easements;
  • If the property is a designated NYC landmark; and
  • There may be other differences that I haven’t noticed.

While some of these characteristics can be calculated, others cannot without City Planning’s involvement (since they maintain the data on parcel-by-parcel zoning and FAR, for example).

Also, there can be some confusion over linking assessment roll tabular data to tax parcel boundaries for tax lots that are condos.  I can discuss this in a separate blog post, or perhaps others can weigh in on this topic.

So the Digital Tax Map plus the assessment roll files are not a complete replacement for MapPLUTO.  That’s one reason this is only a partial victory.  I would imagine that the information in these combined files will enable many groups and individuals to avoid using MapPLUTO completely.  But other organizations that rely on characteristics such as FAR, detailed zoning, easements, etc will still need the more complete MapPLUTO package.

We still need to Free MapPLUTO

But the availability of the Digital Tax Map shapefiles greatly undercuts City Planning’s ability to levy fees and impose license restrictions on the public for this data so essential to understanding our city.  It underscores how unnecessary it was for City Planning to be involved in selling the data in the first place.  For several years now the tax parcel boundaries have been maintained by the Dept of Finance, and the assessment roll data that provides the bulk of PLUTO is created and maintained by Finance too.  So why has City Planning been selling data from other agencies as its own?

It also begs the question: now that the Digital Tax Map and the assessment roll data is free online, why is City Planning still selling/licensing MapPLUTO?  Is this an oversight on their part?  Or does City Planning think they that an unaware public will still come to them for MapPLUTO so they can extract more fees?  Either way the fees for MapPLUTO should end immediately, even if it requires the Mayor’s office to step in and require his agencies to comply with Local Law 11.

And it would be more than a nice gesture if the city refunded the past decade’s worth of license fees the city has collected on the backs of local community groups, academic institutions, students, and others who’ve had to pay City Planning in order to access mapped tax parcel data.

Communication to help bridge the data gap?

Btw, while it’s wonderful the Digital Tax Map files are now available online, I wonder why it took my blog post to reveal the availability of the files?

I’ve known for some time that the Dept of Information Technology and Telecommunications (DoITT) maintains an interactive map displaying the tax parcel boundaries.  But there’s no download option at that mapping site for the boundary data.

Also, I regularly check the Finance Department’s website where you can download the assessment roll data.  Even today, there’s no mention that the Digital Tax Map is available for free online.  Nor does the Finance Department’s web page explaining the Digital Tax Map project mention anything about a download option.

I also regularly search the city’s Open Data Portal, but I hadn’t come across the Digital Tax Map file until Colin posted a comment today at my blog.  If you sort the Open Data list by “Newest” or “Recently Updated”, the Digital Tax Map doesn’t show up in the first several pages.

I think this speaks to the need for communication between the agencies that create the data, and the various constituencies of groups that use (or might hope to use) the city’s data sets.  Simply posting something to the portal is not enough.  If the city truly wants to foster innovation by making its data files more open, it would help if either the agencies or the Mayor’s office or some entity within city government provided regular communication about data that’s available, how to use it, what it shouldn’t be used for, etc.

Nonetheless, the city has taken an important step in opening up access to tax parcel information with the Digital Tax Map.  Looking forward to more to come!

A Modest Proposal for NYC Tax Parcel Data

On behalf of all the urban planning students, local nonprofits, neighborhood groups, Community Boards, journalists, and others who’ve paid cold hard cash to the NYC Department of City Planning for the “privilege” of having license-restricted access to the city’s tax parcel data, I’d like to make a modest proposal:

New York City’s Planning Department should refund the fees they’ve collected for the past decade from all of MapPLUTO’s licensees, and  MapPLUTO should be posted online for free downloading.

We’re talking real money for many local groups

The MapPLUTO database was conceived by City Planning circa 2003 as the successor to earlier efforts to license and sell tax parcel boundaries.

Based on an article this week from The New York World, City Planning has collected up to $80,000 a year from the sale of MapPLUTO data.  Over a decade, that’s $800,000.  According to a response from City Planning to a Freedom of Information Law (FOIL) request by 596 Acres for a list of all PLUTO licensees from 2003 to 2012, there have been almost 400 licensees (including several dozen city agencies, which I’ll discuss separately below).

It’s hard to say the exact amounts that each group has paid to City Planning; as far as I know, City Planning has never released a full accounting of the fees they’ve received from MapPLUTO licenses.  In this era of transparent government, we should be able to find this out.  But this information is hidden behind City Planning’s walls.  Even a search for “MapPLUTO” or “PLUTO” at CheckbookNYC reveals nothing.

I do know that my organization, the Center for Urban Research at The Graduate Center / CUNY, has spent $7,500 in MapPLUTO license fees since 2006.  Before that, the mapping project I co-founded at NYPIRG also licensed MapPLUTO and paid City Planning several thousand dollars over several years.

That’s real money, especially to a nonprofit group and modest academic research center.  And it’s money I think we – and all the other MapPLUTO licensees – never should have had to pay.

(Note: my critique shouldn’t detract from the great work that the Dept of City Planning does in so many other areas, including the other data sets that the agency makes available for free online.)

Why does the Dept of City Planning restrict access to such an important database?

This week’s New York World article highlights the absurdity of the city’s efforts to charge fees for the data.  MapPLUTO is based on data that City Planning obtains from other city agencies. It’s not new data. It’s not data that has been created so that City Planning can sell it.  It’s data that’s been compiled using taxpayer dollars, for the purposes of land use analysis and planning.  The data has already been paid for by the public, and the Planning Department shouldn’t be justified in charging extra for it.

City Planning has worked hard to keep a lock on the fees they receive (though as I understand it, the Planning Department doesn’t even receive the fees directly – the funds are put in the city’s general fund):

  • The Planning Department requires MapPLUTO users to sign a license agreement that prohibits any kind of sharing or reuse of the data.
  • According to the agreement, “unlicensed third parties” cannot have access to the data.
  • There’s an additional prohibition for distributing the “geographic coordinates” contained in MapPLUTO – i.e, the GIS representation of tax parcel boundaries that you need to map the data and analyze it spatially.
  • Using the data for a product that will be resold (such as a mobile app) is prohibited.
  • And MapPLUTO “or any of its components” cannot be “place[d]… on the Internet.”

Now that the city’s Open Data Law requires agencies to post data online, City Planning is falling back on the argument that since the MapPLUTO data comes from other agencies, they don’t have to post it (an exemption in the law).  It’s up to the other agencies to do so.  But as Dominic Mauro from the Transparency Working Group puts it:

If you’re getting paid for this data, I don’t see how they can reasonably claim that this is not their data.

In other words, City Planning can’t have it both ways.

City Planning also claims copyright over the MapPLUTO data.  I’m all for giving credit where credit is due – City Planning should be cited whenever MapPLUTO data is used (and for that matter, all the individual agencies from whom City Planning gets the data should be cited as well).  But why control what can be done with the data?  Why limit its use?  This just stifles innovation and entrepreneurship, not to mention any local community planning work that might be prohibited by the license or by copyright.

Indeed, allowing app developers, realtors, architectural firms, consulting groups, and any other for-profit entity to use the city’s tax parcel data at no cost and with no restrictions can only help the city.  Removing these restrictions opens up business opportunities, and with business growth comes job creation and tax revenue, precisely the kinds of things that our current Mayor has been keen on promoting.

And removing barriers to MapPLUTO makes it easier for nonprofits, academic institutions, and students to engage in local planning efforts on a level playing field.  If only groups that can afford the data can use it, the rest of us are at a disadvantage.

Will the city actually enforce its restrictive practices?

What if you decide to ignore the license or copyright restrictions? City Planning reserves its right to come after you.  According to the New York World article, the Department of City Planning says that “Any such use without a license could give rise to an enforcement action.”

An “enforcement action”?  Really?  When Mayor Bloomberg signed Local Law 11, he said “If we’re going to continue leading the country in innovation and transparency, we’re going to have to make sure that all New Yorkers have access to the data that drives our City.”   I don’t think there’s any dispute that real estate is one of the key drivers of the city.  So I wonder if Mayor Bloomberg’s planning agency would go after a NYC BigApps entrant who uses MapPLUTO data in a web-based app?  Would the Mayor approve of City Planning suing a local nonprofit group that posts the data online? Would he let City Planning take enforcement action against Cornell University if Cornell’s new technology campus developed a profitable product that relied on MapPLUTO data?

And from the perspective of investing tax dollars, would city funds be best spent on lawsuits, or on facilitating innovation?

You’re not alone: other city agencies have paid for MapPLUTO, too!

City Planning’s efforts to control access to MapPLUTO data haven’t been reserved only for those outside city government.  The Planning Department has even imposed its restrictions and fees on other city agencies.

According to the list of MapPLUTO licensees uncovered by 596 Acres, City Planning has issued licenses to the Mayor’s Office, the Dept of Information Technology and Telecommuncations (DoITT), the Office of Emergency Management (OEM), the Police Department, the Law Department (presumably they’re the ones who need to review the license in the first place!), the City Council, and several Community Boards.

What possible reason could City Planning have for wanting or needing to know how and why these agencies are using MapPLUTO data?  Why should city agencies need to license data from another city agency?  And some of these agencies – especially Dept of Finance, but also Parks and Recreation, the Dept of Citywide Administrative Services (DCAS), and the Landmarks Commission – are the very agencies that City Planning gets the data from to create MapPLUTO in the first place!

Not to pile on (but it’s so easy to do with such an absurd situation), City Planning historically has not only required licenses from other city agencies, but City Planning previously required other agencies to pay a fee to obtain tax parcel boundary files.  In 2000, for example, not only were the fees for tax parcel data files higher ($1,150 per borough, rather than the current $300/borough fee), but the fees were “$750 per borough for New York City agencies”.

That must’ve made for some interesting discussions among agency heads during budget time.  As far as I know, that practice ended soon thereafter.  But it’s evidence of City Planning’s inexplicable and ongoing effort to control access to tax parcel data, and to try to profit from it, even from their own colleagues in city government.

Tear down the paywall (and offer some payback while you’re at it)

Now that the city has a law requiring data to be freely available online, there’s strong justification for removing the fees and the license requirements and copyright restrictions.  But frankly, we’ve already had a law requiring data such as MapPLUTO to be made available with no restrictions and for no more than the cost of distribution (such as what it could cost to copy the files to a DVD or to post them online).  That’s the New York State Freedom of Information Law, in effect since the mid-1970s.

What’s especially curious – and frustrating – about City Planning’s persistence in restricting access to tax parcel data is that the agency has made great strides in opening up access to other data sets it maintains.

A decade ago City Planning was charging fees to the public and other agencies for data as simple as a GIS file representing borough boundaries, or Census tract boundaries, or Community Boards.  One by one the agency has removed these fees and developed what I consider a model website for making agency data publicly accessible: the “Bytes of the Big Apple” website (overly cute name for a very useful site).

Even as recently as Fall 2012, the Planning Department removed the fee it had been charging for its “Geosupport Desktop Edition”, a software and data package that takes a list of street addresses and returns information about each address’s building ID, tax parcel ID, and more.  City Planning previously was selling this package for $2,500 a year (and more if you wanted more frequent updates).  In terms of the time involved by City Planning to create this application, maintain it, and keep it updated, I would imagine it’s worth much more than the effort to update the MapPLUTO data.  Yet “Geosupport” is now free, but we still have to pay for MapPLUTO.  I don’t get it.

Free MapPLUTO!

The time is right for the Department of City Planning to change its ways regarding MapPLUTO – the one remaining major data set it licenses for a fee.  I think City Planning should take two simple steps:

  1. immediately remove any fees and restrictions on MapPLUTO (and post the data online for anyone to download it); and
  2. refund all its MapPLUTO fees from the last 10 years.   The city should think of this as a relatively small but important investment in innovation and entrepreneurship.  And it would be a way of apologizing to all the groups and individuals who’ve effectively paid taxes twice on this information that’s so essential to understanding land use and real estate – arguably the lifeblood of the city.

Such a sensible proposal!

But what if City Planning continues to dig in its heels?  Perhaps you can try the Freedom of Information route and request the data via FOIL.  That’s what 596 Acres did, and they received MapPLUTO for a mere $5 fee!  City Planning still claimed copyright restrictions, but maybe if City Planning receives enough FOIL requests they’ll be persuaded that there’s no point in maintaining MapPLUTO’s high fees and restrictive licenses.  Here’s the link http://www.nyc.gov/html/dcp/html/about/location.shtml#foil

Interactive “Comparinator” maps launched for NYC Council districting

UPDATE Sept 7, 2012

The City Council Comparinator site is now embeddable for your website, blog, etc.

Here’s how to use it:

  • go to the site,
  • zoom to a district and click to highlight it (or enter a street address),
  • choose one of the tabs above the map (Side-by-Side vs Overlay, for example), and
  • pick which proposal you’re comparing with (Districting Commission or Unity Plan).
  • Then click “Link” in the upper right and you’ll see the embed code as well as the basic linking code.

Sample embed code:

We also added a feature: if you turn off the popup window before clicking “Link”, it’ll add a “popup=false” property to the URL, so the person viewing the link (or the starting image for your embedded map) won’t have the popup in the way but the district will still be highlighted.

Here’s an example:

ORIGINAL POST Sept 5, 2012:

NYC Council Districting and You

How existing City Council districts compare with proposed lines


Our Center for Urban Research (CUR) at the CUNY Graduate Center has launched an interactive map today to visualize proposed New York City Council districts compared with existing ones along with the demographic characteristics and patterns within the districts.

The Center hopes the map will help involve people in the NYC districting process simply by showing them how proposed or newly drawn lines looked in relation to their homes or workplaces. Our map is not for drawing districts; others such as the NYC Districting Commission are providing that service.   But CUR’s comparison maps are designed to be be engaging enough to visualize the impact of redistricting for everyone from local citizens to redistricting professionals, hopefully inspiring people to participate more actively in the process.

CUR’s map was designed and is being maintained independently from the NYC Districting Commission’s website. However, we hope that people who use CUR’s maps will then access the Districting Commission’s website for drawing maps online.

Using the map

The main features of the map are as follows:

  • Enter your address to find out what district currently represents you, and which proposed district you’d live in.
  • If you’re using the “Side-by-Side” view, the current districts are displayed on the left, and the proposed districts on the right.
  • If you’re using the “Overlay” view, you can move the transparency slider to the right to display proposed districts, or to the left to fade back to current districts.
  • Click anywhere on the map to highlight the current and proposed districts.
  • When you enter an address or click on the map, an info window pops up listing the current and proposed districts. You can click the link for the current district to go to that Councilmember’s website.
  • Click the “Link” in the upper right of the page to get a direct link to the area of the map you’re viewing. (This one zooms in on City Council District 8 in Manhattan.) You can share this on Twitter or Facebook, email it to friends and colleagues, or blog about it and include the link.


The mapping application was developed by the Center for Urban Research. David Burgoon, CUR’s application architect, constructed and designed the site, with data analysis support and overall conception from CUR’s Mapping Service director Steven Romalewski.

The application relies on geographic data hosting by cartoDB, open source mapping frameworks and services including OpenLayers and Bing maps, and ESRI’s ArcGIS software for cartography and data analysis.

Data sources

Current City Council district boundaries and proposed maps from the NYC Districting Commission are based on block assignment lists provided at the Districting Commission’s website.

Other proposed maps such as the Unity Map are provided by the advocacy organizations who developed those proposals.

Citi Bike NYC: the first and last mile quantified

The NYC Department of Transportation revealed last week where they’d like to place 400 or so bike share stations in Manhattan and parts of Brooklyn and Queens, as the next step in the city’s new bikeshare program starting this summer.  (By next spring the city plans to locate a total of 600 bike share kiosks for 10,000 bikes.)

Several blogs and news reports have criticized the cost of the program as too expensive for relatively long bike trips (more than 45 minutes). But the program is really designed primarily for the “first and last mile” of local commutes and tourist trips to and from their destinations.  Now that the city’s map is out, we can evaluate how likely it is that the locations will meet this goal.

Subway and bus proximity

Last year I examined the thousands of bike share kiosks suggested by “the crowd” to see how closely they were located to subway entrances.  I determined that, as of late September 2011 based on almost 6,000 suggestions, one-third of the suggested sites were within 500 feet (actually, if I had used 750 feet — the average distance between avenues in Manhattan — it would’ve been 45% of the suggested sites located that distance or closer to a subway entrance).  You can still see the crowdsourced locations here.

So about half of “the crowd’s” suggestions were close to public transit, and the other half further away.  That seems reasonable — perhaps half the suggesters were thinking of how to link bike share with the subway system, and the other half was thinking about linking bike share to destination sites further away from mass transit.

Here’s my map from last year of the subway entrances symbolized based on the ratings of the closest suggested bike share kiosks.  This map says, “If you want to put bikeshare stations near subway entrances, these are the entrances you’d pick based on the average rating of the closest stations suggested by the crowd”:

I had suggested this as a way of prioritizing the bikeshare station siting process.  These subway entrances are the ones you’d likely start with, based on the preferences of the (bike)riding public who contributed to the DOT/OpenPlans map.

But now that the bikeshare station siting process is pretty much done, I’ve examined whether the proposed kiosks are close enough to subway and bus stops to actually facilitate their use by the intended audiences.

How do the actual proposed locations measure up?

For me, the city’s proposed bike share program is a great deal — if the kiosks are near my home and my office.  I live on Manhattan’s west side and work in midtown.  Since I live near my office I’m lucky to have a pretty easy commute.  But usually that involves a good amount of walking: my trip uptown is just one subway stop, and then going crosstown involves either a bus (luckily the M34 Select Bus is pretty reliable) or a schlep walk of several avenues.  Don’t get me wrong — walking is great exercise.  But if I could shorten the walk and save money, I’m all in.

According to DOT’s map [PDF], there’s a bike share kiosk proposed down the block from my apartment, and another one a block from my office.  Nice!  I could actually replace the subway/bus combo with a bike ride for a fraction of the cost.  But what about the rest of the Phase 1 area?  Are the kiosk locations designed to easily extend subway and bus trips for the “last mile”?

Here’s what I found: most of the proposed bikeshare locations are relatively close to subway entrances, and even more are closer to bus stops.  At least regarding the locations, the system seems right on track to meet its goals of facilitating New York’s commuter and tourist trips.

Here’s what I measured

The DOT bike share website displays the proposed kiosks on a Google Map.  But a separate URL lists the lat/lons of each site (in JSON format).  There are 414 bike share lat/lons at this URL (not the 420 that all the news accounts referenced), and one location has a lat/lon of zero (ID 12405), so I deleted it leaving me with 413 locations.  (I used Google Refine to convert the JSON file to CSV and imported it to ArcGIS to analyze the locations.)

But this data just shows the locations. It omits information about each site (such as “North side of East 47th Street near Madison Avenue “), and the number of bike “docks” at each proposed kiosk.  Separately, Brian Abelson wrote a script to access this information from DOT’s website, based on a URL that looks like this:


(His R script is here: https://gist.github.com/2690803 .  With this data I was able to map the kiosks based on number of docks at each one; see map below.  Big thanks to Brian!)

Here’s an interactive version (thanks to cartoDB), and here are links if you’d like to download the file in GIS format:

Proximity to subways

Here’s the map of proposed kiosks in relation to the closest subway entrances (based on the latest data from MTA on subway entrances/exits); I used ArcGIS’s “Near” function to calculate the distance:

Here are the stats:

  • 89 locations (22%) between 14 and 250 feet (length of a typical Manhattan block);
  • 117 kiosks (28%) between 250 and 750 feet (the average distance between Manhattan avenues);
  • 97 kiosks (24%) between 750 and 1,320 ft (a quarter mile);
  • 89 kiosks (22%) between 1,320 and 2,640 ft (a half mile); and
  • 21 kiosks (5%) further than 2,640  feet.

(The percentages do not equal 100% due to rounding.)


  • The proposed kiosk closest to a subway entrance is in lower Manhattan, on the west side of Greenwich St near Rector St (ID 12364), 14 feet from the Rector St entrance to the 1 train.
  • The kiosk furthest from a subway entrance is on Manhattan’s west side, in the Hudson River Greenway near West 40th Street (at the West Midtown Ferry Terminal; ID 12092), almost three-quarters of a mile (3,742 feet) from the 40th St entrance to the 42nd St/Port Authority Bus Terminal station.

In other words, half of the proposed kiosks are within an avenue of a subway entrance, one-quarter are within two avenues, and the rest are further away.

So I guess it depends on your level of optimism (glass half full or half empty), and/or how far you’re willing to walk between your destination and a bike rack to participate in the Citi Bike program.  But in general it seems that the proposed kiosks match the overall location patterns of the crowdsourced suggestions, and also support the goal of facilitating first/last mile transportation.

Proximity to buses

Here’s the map of proposed kiosks in relation to the closest bus stops (based on the latest data from MTA / ZIP file).  Note that I didn’t differentiate between local, limited, or express bus stops.  As with subway entrances, I used ArcGIS’s “Near” function to calculate the distance:

For bus riders, the bike share locations are even better suited than subway riders to help them go the last mile:

  • 55 proposed kiosks (13%) between 27 and 100 feet (less than a typical Manhattan block);
  • a whopping 199 kiosks (48%) between 100 and 250 feet (length of a typical block);
  • 139 kiosks (34%) between 250 and 750 ft  (typical distance between Manhattan avenues);
  • 16 kiosks (4%) between 750 and 1,320 ft (quarter mile); and
  • only 4 kiosks (1%) further than 1,320 ft — and none further than 1,652 feet away (about a third of a mile);

So for bus riders, almost two-thirds of the proposed kiosks are within a block of a bus stop, and almost all of them (95%) are within an avenue.  Pretty good odds that bus riders will have extremely convenient access to the Citi Bike program.

I was skeptical of the program at first (and I’m still a bit wary of so many more bikes on the road all of a sudden — I walk in fear when I cross a city street, because of cars and bikes).  But now that the Citi Bike program is moving closer to reality and the numbers look so good, I’m looking forward to trying it out.

Proposed Congressional districts for NYS available in GIS format

UPDATE June 25, 2012

We launched a companion map featuring Congressional districts with statistics on eligible voters by race/ethnicity compared with total population.

UPDATE March 6, 2012

We’ve added Congressional districts as proposed by District Court Judge Hon. Roanne Mann to our interactive redistricting site. Here’s a link that compares District 9 (Rep. Turner, in NYC) with one of the proposed districts that it would become under her proposed lines: http://t.co/01K4hMu8

We also submitted a letter today to the court [PDF] suggesting that they can use our maps to visually compare the different proposed lines.  Hopefully they’ll put our online maps to good use as they review the different Congressional district proposals.

UPDATE March 5, 2012

We’ve made two updates the information below.

  1. We’ve added the Congressional district data in shapefile and KMZ formats based on Common Cause’s submission to the court.  We think this will be especially helpful since the court has asked the intervenors to compare their maps with Common Cause’s proposal.
  2. Now you can visualize the proposed districts based on the mapped data below at the Center for Urban Research’s interactive redistricting site.
    1. compare with existing Congressional districts;
    2. easily switch among the Congressional proposals from Common Cause and the Senate & Assembly majorities; and
    3. view the proposed districts in relation to block-level demographic maps (do any of them appear to “pack,” “crack,” or dilute the potential voting power of minority populations?) or local voting patterns (click the “More Data” tab at the bottom right).

Here are some examples:

Today the New York World posted an analysis of how these different Congressional district proposals might impact Rep. Charles Rangel’s current district 15.

Original Post

If you’re hoping to use GIS or any of the online mapping tools to map the Congressional district lines in New York State that were proposed late yesterday, you’ll have some work to do.  The maps were released in PDF format as well as “block assignment lists” for the proposed districts.

But if you’d like to use shapefiles and/or KML files, you’ve come to right place!  Our team at the CUNY Graduate Center has created them and posted them for downloading here:


We hope to add these soon to our interactive redistricting map. Stay tuned!

NYC’s open data legislation: reading between the lines

TL; DR (i.e., the summary)

NYC is about to adopt what some are calling “landmark” and “historic” legislation regarding open data.  Does the hype match the reality?

I offer the analysis below not as a critique of the City Council.  I think they probably tried to negotiate as good a bill as they thought they could achieve.  I offer it more as food for thought for those of us who will be seeking the data that may eventually become available because of the legislation (and for those of us who rely on data that’s currently available that may become less so due to the bill).

Hopefully my concerns represent a worst case scenario.  If the bill’s implementation indeed lives up to the “landmark” status bestowed on its passage, that would be a great thing.

For example, the Council’s committee report on the bill [Word doc] suggested that substantial city data sets such as the Building Information System (BIS) or the Automated City Register Information System (ACRIS) would be made available in open, accessible formats due to the legislation. If that happens, that would be great.  But for each of the handful of examples like that suggested at yesterday’s Council committee meeting, I could offer several more that I believe might escape the requirements of this bill.

My overall sense is that somewhere during the two-plus years the bill has been on the table, the details got in the way of the original vision embodied in this proposal.  And, as they say, the devil is in the details.  If you’re interested in my take on those gory details, please read on.

An important step

The bill is important, in a way. It’s an acknowledgment by the City Council (and the Mayor, if he signs it) that city agencies need to provide public access to data sets online, in a standardized electronic format.

In doing so, it goes a step beyond FOIL — the New York State law since the mid-1970s that has required agencies (including local government) to provide public access to data.  Though FOIL has adapted to the times to some extent — the courts and policymakers now understand that FOIL applies to electronic data as well as printed material — it is still a reactive approach.  You have to submit a FOIL request (and have a good idea of what data you’re requesting) for an agency to respond and give you access.  New York’s Committee on Open Government describes it as “pull” vs. “push”. [PDF]

Some smart agencies have realized that posting data electronically saves money, time, and effort. By posting data online proactively, before the agency even receives a single FOIL letter  (“pushing” it so people don’t have to “pull” it), it avoids having to respond individually to FOIL requests.

So the City Council bill acknowledges that pushing is better than pulling.

Those devilish details

But will the legislation require agencies to post data online?  To some extent, yes.  But how far that goes depends on how it’s interpreted, and how aggressively it’s implemented (and perhaps how strongly the public reacts, since it seems like the only enforcement mechanism is public reaction).

The first substantive part of the bill says that within a year, agencies need to post their data at the city’s online data portal.  But let’s look closely at the language.  Section 23-502(a) says that within a year, agencies don’t need to publish all their data to the portal.  Only “the public data sets that agencies make available on the Internet” need to be included in the portal (emphasis mine).

In other words, if an agency has refused to provide public access to a data set, or perhaps only allows access to that data after you’ve paid a fee and/or signed a license agreement, or otherwise hasn’t already posted the data online — that data is exempt.

Then it gives agencies another loophole.  The next sentence says that even if an agency has a data set online, it doesn’t need to post it on the portal if they “cannot” put it on the portal.  (“Cannot” isn’t defined in the bill.  Does it mean “doesn’t want to”? Does it mean the data’s too complex for some reason?  “Cannot” seems to offer quite a bit of wiggle room.)

The bill further states:

the agency shall report to the department and to the council which public data set or sets that it is unable to make available, the reasons why it cannot do so and the date by which the agency expects that such public data set or sets will be available on the single web portal.

I’m not a lawyer, but it seems to me that if an agency doesn’t want to comply, it just needs to give a reason.  And it needs to give a date by when it will add the data to the portal.  The date could be two years from now, or it could be two decades from now.  That part of the bill doesn’t have a deadline.

Without aggressive support from the top — the Mayor and/or perhaps a new Chief Data Officer position with some teeth — agencies could just take their ball and go home and not play the open data game.  And the public will be the worse for it without much recourse.

Over-reliance on “the portal”

Let’s be optimistic and assume that all city agencies (even the current holdouts – I’m looking at you, City Planning Department & MapPLUTO) decide to post their data online.

The bill doesn’t say, or even mention as an option, that agencies can keep posting the data online at their own websites.  Instead, it has to be posted on “a single web portal that is linked to nyc.gov”.

But I’m not as enthusiastic as I once was for the portal approach (currently implemented here).

  1. Data for APIs, or people?

At first I thought the portal would be so much better than the city’s earlier Datamine site. But the site seems to focus heavily on APIs and web service access to the data, which might be great for programmers and app developers, but not so good for people, like Community Board staff, or reporters, or students, or anyone else who just wants to download the data and work with the files themselves.

  1. Some agency websites are doing a better job

Also, why not allow — even encourage — agencies to continue posting data on their own websites?  I think that, in many instances, the individual agencies are doing a better job than the data portal. The files available for downloading from agency sites such as Finance, City Planning, Buildings, and Health are more up to date, more comprehensive (though still hardly complete), and easier to understand than what I can find on the portal.

I think it would be ok if both approaches existed (portal and individual agency sites). But the way the bill is worded, I think the risk is that agencies are more likely to do only what they have to do or what they’re expected to do.  Since the bill focuses on the portal, I think we may see individual agency data sites whither away, the rationale being why bother with individual sites since they have to post to the portal.  With sites such as City Planning’s Bytes of the Big Apple (which is really great, with the exception of the PLUTO license/fee), I think that could be a big loss for the many people and organizations who have come to rely on the high quality data access that these agency sites provide.  Hopefully I’ll be proven wrong.

  1. The current portal falls far short of a forum for public discussion

The bill requires DoITT to

implement an on-line forum to solicit feedback from the public and to encourage public discussion on open data policies and public data set availability on the web portal.

But if the current portal is the model for this online forum, I’m concerned.

When I access data from the agencies themselves, I can talk with the people directly responsible for creating and maintaining the data I’m seeking. I can have conversations with them to understand the data’s limitations. I can discuss with them how I’m planning to use the data, and if they think my expectations of the data are realistic.

In contrast, the portal requires me to either go through a web form (which I’ve done, and received zero communication in return), or to contact someone who has no identification beyond their name (or some online handle).  Do they work for an agency?  Do they even work for New York City?  I have no idea; the portal provides no information.  So much for a site that’s supposed to be promoting “transparency in government.”

To me, the portal is somewhat analogous to the city’s 311 system and the recent articles about putting the city’s Green Book online.  Though 311 is great in a lot of ways, it has put a wall between the public and individual city agency staff members.  Try finding a specific staffperson’s contact information via nyc.gov, like the New York Times recently did.  It’s almost impossible; you have to communicate through 311. Similarly, the online data portal — if it ends up replacing agency websites as sources for online data access — will make it difficult to locate someone knowledgeable about the data.

This widens the “data gap” — the gap of knowledge between data creators and data users.  In order to know whether a particular data set meets my needs (if I’m creating an app, or even just writing a term paper), sometimes a written description of the data is not enough.  I may need to actually talk with someone about the data set.

But good luck finding that person through the data portal.

And even when people have used the portal to submit online comments, I don’t know if anything ever comes of it.  It looks like only 14 of the 800+ datasets at the portal have comments (sort the list by “Most Comments”).  All of the comments raise important questions about the data.  For example, two people offered comments about the HPD Registration data available through the portal.  They asked “Is there any plan to expand it?” and “Could you help us?”  Both remain unanswered.

Maybe everyone who commented was contacted “offline”, as they say.  Either way, this hardly constitutes a forum for public discussion.  No public interactivity.  No transparency.  No guidance.  It’s no wonder there’s been so little use of the portal’s  button (and I use the term “Discuss” loosely).

Public data inventory

Another section of the bill has a nugget of hope.  But the way it’s worded, I’m not too optimistic.

Section 23-506(a) says that within 18 months, DoITT shall present a “compliance plan” to the Mayor, the Council, and the public.  Among other things, the plan must “include a summary description of public data sets under the control of each agency.”

In effect, this “summary description” (if it’s done right) will be the public data inventory that advocates have been pushing for (and which has been required by the NYC Charter since 1989). That’s a good thing. At least now we’ll know what data sets each agency maintains.

Hopefully it’ll be a comprehensive list. I guess the list’s comprehensiveness will be up to DoITT to enforce. (And if the list comes up obviously short, perhaps some enterprising FOILers can point out — very publicly — where the holes are 😉 ).

But that same section of the bill also says that the plan “shall prioritize such public data sets for inclusion on the single web portal on or before December 31, 2018“.  So it still relies solely on the data portal. And it gives the city another 6 years to make the data public. As someone said on Twitter, “sheesh”!

Then there’s another loophole.  The bill allows agencies to avoid meeting even the 2018 deadline by allowing them to

state the reasons why such [public data] set or sets cannot be made available, and, to the extent practicable, the date by which the agency that owns the data believes that it will be available on the single web portal.

“[T]o the extent practicable”?  When the agency “believes” it’ll be available?  Wow.  Those are some loose terms.  If I ran an agency and didn’t want to provide online access to my department’s data, I’d probably feel pretty confident I could continue preventing public access while easily complying with the law.

Where does this all leave us?

It looks like the City Council will pass this law, despite its limitations.  In fact, DoITT was so confident the law will pass, it emailed its February 2012 newsletter on the day the Council’s technology committee voted on the bill (Feb. 28, a day ahead of the expected full Council vote).  Here’s what the newsletter said about Intro 29-A:

“Will be voted on and then passed”?  I guess the full Council vote is pretty much a foregone conclusion.

That leaves us to hope that the bill’s implementation will address the issues I’ve outlined above, and any others that advocates may have identified.  Fingers crossed?

(Disclaimer: my viewpoints on this blog are my own, not necessarily my employer’s.)

Redistricting’s partisan impacts: a GIS analysis

Our team at the Center for Urban Research is collaborating with The New York World to analyze the impacts of redistricting in New York State.  The latest effort was featured today on the front page of the Times Union; it focuses on how the majority parties in the State Senate and Assembly would likely retain — and strengthen — their control of both houses through the redrawn district lines.

Briefly, we found that the new boundaries for state Senate and Assembly districts proposed by LATFOR would increase the number of seats held by the majority parties in both chambers.  We based the analysis on 2010 election data available from LATFOR’s website.  The goal was to determine the results of state legislative elections held within the new districts if voters cast their ballots in the exact same way as they did in 2010, the most recent election year for State Senate and Assembly.

  • In the State Senate, the Republican Party’s 32-to-30 majority would expand to 34-to-29 if each voter cast his or her ballot in support of the same party as in the 2010 elections.
  • In the State Assembly, the 98-to-50 advantage the Democrats enjoyed following 2010’s elections would also increase, to 102-to-48.

The project was a good example of the power of GIS.  The analysis didn’t necessarily need a map to display the results (though Michael Keller at the NY World put together a nice one). But the analysis effectively wouldn’t have been possible without GIS.

Converting Polygons to Points

We analyzed election results at the level of voter tabulation districts, or VTDs, which are several blocks in size and typically cast no more than a few hundred votes in state legislative elections.  We mapped the VTDs onto the new lines proposed by LATFOR, then added up the votes of all VTDs that fell within a proposed district to determine its outcome.

In order to allocate the VTD-level vote counts to LATFOR’s proposed districts, CUR matched VTDs spatially with the current and proposed legislative district using ESRI’s ArcGIS Desktop software. The current and proposed Senate and Assembly districts are coterminous with Census blocks (in fact, the districts are “built” using Census blocks).  Unfortunately, neither LATFOR nor the state’s Board of Elections provides election results at the block level.  The Board of Elections records data by election district, which sometimes are smaller than VTDs, but for this project we did not have access to the election district data.

The challenge was that where the VTDs were larger than Census blocks in some places, the VTD boundaries crisscrossed the district lines (see example at right from Queens; click to enlarge).  In order to assign Senate and Assembly district IDs to each VTD, CUR converted the VTD boundaries to centroids (the geographic center-point of each VTD).  We used the lat/lon centroid values provided by the Census Bureau’s TIGER data.  Then we used a spatial join using ArcGIS to add legislative district identifiers to each VTD based on the legislative district its centroid was inside.  See the image below for the locations of the VTD centroids in this area of Queens.

In the instances where VTDs crisscross legislative districts, this technique will allocate all of a VTD’s votes to a single legislative district rather than splitting them across multiple districts.  This will over- and underestimate vote totals in some districts. But the process avoids the cumbersome effort involved in the alternative: splitting VTD vote counts.  The splitting process uses one of two methods:

  • using block-level population to “spread” the VTD votes across the VTD (multiplying the VTD vote count by the percentage of the VTD population occupied by each block and assigning the result to each block), or
  • weighting the VTD vote count based on the area of the portion of the VTD in each district.

Either of these approaches will result in fractions of people being assigned to one legislative district or another.  In fact, LATFOR appears to have used some sort of weighting method to assign election district vote counts to VTDs, since some of LATFOR’s VTD vote totals included fractions.

The centroid-approach and the weighted population / area approach both make assumptions about how to allocate vote counts.  But we tested the centroid process with current legislative districts and found that our VTD-allocated vote totals either exactly matched the results from the Board of Elections or were within a few hundred votes (which did not change the 2010 outcome).

Whether we used the centroid-approach and the weighted population / area technique, it otherwise would’ve been difficult if not impossible to determine how to allocate the VTD-level vote counts to legislative districts without GIS.  There are almost 15,000 VTDs across New York State, and there are (currently) 62 Senate districts and 150 Assembly districts.  With GIS, the process was relatively straightforward and efficient.

Aggregating by District

At the VTD-level, LATFOR provides the total number of votes cast by party in each election, not by candidate.  One challenge that we confronted was assigning the votes cast for fusion candidates who were backed by a major party but also received support on smaller parties’ ballot lines.  For example, many Democratic candidates received significant numbers of votes on the Working Families Party ballot line, and many Republicans got substantial support on the Conservative Party line.  Cross-party endorsements were even more variable for the Independence Party: in some districts, the Democrat received support on the Independence Party line; in others, its endorsement went to the Republican.

We decided that the most accurate way to re-map the election results was to assign the votes for each VTD based on the actual vote patterns for the Senate or Assembly district that contained that VTD in 2010.  In other words, if the Democratic candidate in an Assembly district ran on the Democratic, Conservative, and Independence lines, we assigned the Democratic, Conservative, and Independence votes in all the VTDs in that district to the Democratic candidate.  When we allocated the VTDs to the proposed Senate and Assembly districts, we added up the votes based on these patterns.  This ensured that the local voting patterns from 2010 were allocated accurately to the proposed districts.

The Results: Maps vs. Plain Old Numbers

The result is that we were able to calculate the number of proposed districts that, all other things being equal, would have had a Democratic winner in the Assembly and a Republican winner in the State Senate.  The important finding is that both parties would have increased their majority — which is especially interesting in the Senate, where the Republicans currently only have a 1-seat majority.  In Albany, the majority in each house is extremely powerful, so holding on to (or improving) those margins is all-important.

Of course, as the New York World/Times Union article points out,

To be sure, no district votes the exactly the same way in consecutive elections: the quality of candidates, changes in the population and the national political climate (which in 2010 favored Republicans) all play important roles. But voting behavior in previous elections offers the best available indication as to how a district is likely to perform.

The map that the New York World published along with the article uses red/blue color-shading to visualize the impact of the voting patterns on the proposed districts.  In the state Senate, the analysis shows the majority party increasing the number of seats by two.  On the map, that result is almost lost in the sea of red districts (most of the Republican seats are in upstate New York and Long Island, where the districts cover much larger areas than the more densely populated and largely Democratic districts in New York City).  The real power of our finding is the change in number: from 32 to 34.  In some ways, that says it all.

Nonetheless, the map (along with CUR’s interactive map comparing current and proposed district boundaries) provides a strong graphic and interactive element to the story, and provides context as you move your mouse over the districts to see the vote totals change from one to the next.

Watch for more analysis as LATFOR publishes its proposed Congressional district lines, and when the final Senate and Assembly districts are drawn.

Interactive NY redistricting map with cartoDB and more

UPDATE Nov. 5, 2012

In preparation for the Nov. 2012 election, many news organizations and others are linking to our interactive State Legislature and Congressional redistricting maps. We’ve posted examples at the Center for Urban Research website.

UPDATE Sept. 7, 2012

We’ve updated our map of redistricted State Senate and Assembly districts, highlighting the differences in race/ethnicity characteristics between total population and voter-eligible population – in other words, comparing the characteristics of all those who live in the new districts versus the smaller group who will be eligible to vote for each district’s representatives.  In some cases the differences are striking.

Our examination of the district-by-district data is available here.

New York State, like all other states, is in the midst of redrawing its legislative district lines. To help you follow along, our team at the Center for Urban Research has launched an interactive redistricting map for New York.  We collaborated with The New York World to develop the maps (though we encourage anyone and everyone to use them!).

The World’s reporters and editors are using our maps to go between the lines and explain how redistricting really works in the Empire State. (Here’s their first piece: The art of redistricting war.)  And we hope you’ll be able to use the maps too, to help answer questions such as:

  • Will you still be represented by the same State Senate or Assembly district you live in now?
  • Will you live in the newly proposed (and controversial) 63rd Senate district?
  • Is your neighborhood, town, or county going to be “carved up” by a new legislative seat?
  • Will your community’s historical voting power be diluted by the new districts?

We have some examples of gerrymandering at our Center’s website. In the meantime, here’s how you can use the maps.

Map features

The maps compare the current and proposed district lines (which our team mapped based on Census block lists published by the state’s redistricting task force, known as LATFOR). Here’s how they work:

  • Enter your address to find out what district currently represents you, and which proposed district you’d live in.
  • The current districts are on the left, and the proposed districts on the right.
  • You can also click on either map to highlight the current and proposed districts. As you move one map, the other moves in sync.
  • When you enter an address or click on the map, an info window pops up listing the current and proposed districts. You can click the link for the current district to go to that Senator or Assemblymember’s website.
  • Switch between State Senate and Assembly districts. Congressional districts will be posted once the data is available from LATFOR.
  • You can zoom in to street level, or zoom out to a statewide view. Switch between a street basemap or an aerial view from Microsoft’s Bing maps to see geographic details.

If you’re using the “Overlay” view, you can move the transparency slider to the right to display proposed districts, and to the left to fade back to current districts. The video below shows how:

If you want to share the map you’ve made, click the “Link” in the upper right of the map page to get a direct link to the area of the map you’re viewing. It will look like this:

  • You can share this on Twitter, Facebook, etc and email it to friends and colleagues.
  • You can also embed the map at your site. Use this link …
  • … or add < &output=embed > to any of the direct links you create, like this:
  • … or wrap the snippet below in an iframe tag (I’d wrap it myself, but wordpress.com strips out iframe tags):
frameborder="0" marginwidth="0" marginheight="0" 
scrolling="no" width="600" height="700"

Side-by-side maps with OpenLayers

We borrowed from our “Census Comparinator” mapping site that Dave Burgoon artfully developed, in order to provide three ways to compare the current and proposed legislative districts:

  • a side-by-side view — two maps that are synced and move as one;
  • an overlay — a single map where you can fade between current and proposed districts; and
  • the vertical “before-and-after” slider approach.

I blogged about the Comparinator approach here and here. John Reiser also gave the technique a shoutout at his “Learning Web Mapping” blog for Rowan University.

With Census data, our “Comparinator” approach helped visualize changing spatial patterns of race/ethnicity trends – in cartographic terms, between two choropleth maps. With legislative districts, the comparison is between two sets of boundary files with no inner fill. So here we’ve set the side-by-side view as the default — we think the side by side maps give the easiest way of visualizing how the districts may change. But we also give you the option of viewing the districts with our vertical slider bar if you’d like, or the overlay.

Behind the scenes

For the proposed districts, we used ArcGIS to create the legislative district shapefiles based on LATFOR’s Census block assignment lists.  The current district boundaries are from the Census Bureau’s TIGER files (here’s the FTP page if you’d like to download the “lower” house districts — in New York, that’s the Assembly — or the “upper” house shapefiles — the State Senate).

We use OpenLayers for the map display and navigation with this application, as we’ve done with most of our other interactive maps. OpenLayers is easy to use, enables us to access Bing map tiles directly (so the basemap performance is smooth), and provides a robust JavaScript library for online maps.

That said, newer approaches such as Leaflet.js enable more interaction such as mouseovers, so we’ve started experimenting with some impressive new tools. More to follow!

One of those new tools is the powerful backend geospatial database engine from the team at Vizzuality: cartoDB. Hosting the legislative district shapefiles on cartoDB provided lots of advantages over hosting the data ourselves or setting up an Amazon cloud instance on our own. cartoDB provides:

  • great performance — not only for the district boundaries, but soon we’ll be adding election district maps to show voting patterns within each Senate and Assembly district. We don’t want to bother with creating pre-rendered tiles for this data. cartoDB will render it speedily on the fly.
  • cartographic flexibility: cartoDB uses cartoCSS for map symbology and labeling. Though there are still some quirks with cartoCSS, it was easy to grasp and it’s basically just CSS, so it makes styling easy if you’re familiar with modern web design. And cartoCSS incorporates scale-dependent rendering as well as attribute-based symbology, which makes it powerful and flexible. CartoCSS can be implemented using the cartoDB management interface, or programmatically.
  • easy data management: if you know SQL — and even better, if you’re familiar with SQL commands with PostGIS — you can quickly and easily modify tables, filter data, and perform spatial operations. (The screenshots at the cartoDB github page offer some examples.) Very cool.
  • scaling: cartoDB uses PostGIS and makes use of Amazon’s platform. So if our maps go viral, we’re ready for the usage spike!
  • open source: if you want to manage your own instance of cartoDB, just download the code and go! Big props to Vizzuality for an amazing geospatial toolkit.

Other thanks go to:

  • LATFOR, the state’s redistricting task force. Whatever you think about their redistricting process, they’ve done a great job with open data. They’ve not only posted the list of Census blocks that make up each proposed legislative district. But they also posted a wealth of data at the Census block level and also at the election district level (with a crosswalk between EDs and Census “voter tabulation districts”). This data is indispensable for visualizing, analyzing, and (hopefully) making sense of the new districts.
  • Dave Burgoon and the CUR team. Dave put together the redistricting mapping site in record time. Although it’s based on work he had already done with the Census Comparinator maps, it still involved substantial modifications and enhancements. But he made it happen as professionally and elegantly as always.
  • The New York World. We had been planning to create an interactive mapping application to build on our Census Comparinator site and to help people visualize the impacts of the redistricting process and demographic changes more broadly.  But the World team – Alyssa Katz, Michael Keller, and Sasha Chavkin – met with us a few weeks ago to discuss how we could collaborate on analyzing and mapping the upcoming district proposals from LATFOR.  The discussion inspired us to roll out a mapping site specific to New York State and focused on comparing the current and proposed districts. We’re thrilled to be able to work closely with them on this project (watch for more maps and data in the near future!).
  • The Hagedorn Foundation. The Foundation has provided funding support for our efforts to map and analyze Census data for a variety of civic engagement purposes, especially for Hagedorn’s Long Island-based grantees but also nationwide. Their support has been essential for us to develop innovative mapping applications like the NYS redistricting maps – not to advocate specific district plans one way or another, but to give local residents and others the tools they need to understand the impact of redistricting and hopefully get involved in the process.