Introduction to PostGIS

Section 5: About our data

The data for this workshop is four shapefiles for New York City, and one attribute table of sociodemographic variables. We’ve loaded our shapefiles as PostGIS tables and will add sociodemographic data later in the workshop.

The following describes the number of records and table attributes for each of our datasets. These attribute values and relationships are fundamental to our future analysis.

To explore the nature of your tables in pgAdmin, right-click a highlighted table and select Properties. You will find a summary of table properties, including a list of table attributes within the Columns tab.

nyc_census_blocks

A census block is the smallest geography for which census data is reported. All higher level census geographies (block groups, tracts, metro areas, counties, etc) can be built from unions of census blocks. We have attached some demographic data to our collection of blocks.

Number of records: 36592

blkid A 15-digit code that uniquely identifies every census block. Eg: 360050001009000
popn_total Total number of people in the census block
popn_white Number of people self-identifying as “White” in the block
popn_black Number of people self-identifying as “Black” in the block
popn_nativ Number of people self-identifying as “Native American” in the block
popn_asian Number of people self-identifying as “Asian” in the block
popn_other Number of people self-identifying with other categories in the block
boroname Name of the New York borough. Manhattan, The Bronx, Brooklyn, Staten Island, Queens
geom Polygon boundary of the block
_images/nyc_census_blocks.png

Black population as a percentage of Total Population

Note

To get census data into GIS, you need to join two pieces of information: the actual data (text), and the boundary files (spatial). There are many options for getting the data, including downloading data and boundaries from the Census Bureau’s American FactFinder.

nyc_neighborhoods

New York has a rich history of neighborhood names and extent. Neighborhoods are social constructs that do not follow lines laid down by the government. For example, the Brooklyn neighborhoods of Carroll Gardens, Red Hook, and Cobble Hill were once collectively known as “South Brooklyn.” And now, depending on which real estate agent you talk to, the same four blocks in the-neighborhood-formerly-known-as-Red-Hook can be referred to as Columbia Heights, Carroll Gardens West, or Red Hook!

Number of records: 129

name Name of the neighborhood
boroname Name of the New York borough. Manhattan, The Bronx, Brooklyn, Staten Island, Queens
geom Polygon boundary of the neighborhood
_images/nyc_neighborhoods.png

The neighborhoods of New York City

nyc_streets

The street centerlines form the transportation network of the city. These streets have been flagged with types in order to distinguish between such thoroughfares as back alleys, arterial streets, freeways, and smaller streets. Desirable areas to live might be on residential streets rather than next to a freeway.

Number of records: 19091

name Name of the street
oneway Is the street one-way? “yes” = yes, “” = no
type Road type. Eg. primary, secondary, residential, motorway
geom Linear centerline of the street
_images/nyc_streets.png

The streets of New York City. Major roads are in red.

nyc_subway_stations

The subway stations link the upper world where people live to the invisible network of subways beneath. As portals to the public transportation system, station locations help determine how easy it is for different people to enter the subway system.

Number of records: 491

name Name of the station
borough Name of the New York borough. Manhattan, The Bronx, Brooklyn, Staten Island, Queens
routes Subway lines that run through this station
transfers Lines you can transfer to via this station
express Stations where express trains stop, “express” = yes, “” = no
geom Point location of the station
_images/nyc_subway_stations.png

Point locations for New York City subway stations

nyc_census_sociodata

There is a rich collection of social-economic data collected during the census process, but only at the larger geography level of census tract. Census blocks combine to form census tracts (and block groups). We have collected some social-economic at a census tract level to answer some of these more interesting questions about New York City.

Note

The nyc_census_sociodata is a data table. We will need to connect it to Census geographies before conducting any spatial analysis.

tractid An 11-digit code that uniquely identifies every census tract. Eg: 36005000100
transit_total Number of workers in the tract
transit_private Number of workers in the tract who use private automobiles / motorcycles
transit_public Number of workers in the tract who take public transit
transit_walk Number of workers in the tract who walk
transit_other Number of workers in the tract who use other forms like walking / biking
transit_none Number of workers in the tract who work from home
transit_time_mins Total number of minutes spent in transit by all workers in the tract (minutes)
family_count Number of familes in the tract
family_income_median Median family income in the tract (dollars)
family_income_mean Average family income in the tract (dollars)
family_income_aggregate Total income of all families in the tract (dollars)
edu_total Number of people with educational history
edu_no_highschool_dipl Number of people with no highschool diploma
edu_highschool_dipl Number of people with highschool diploma and no further education
edu_college_dipl Number of people with college diploma and no further education
edu_graduate_dipl Number of people with graduate school diploma


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