source: trunk/workshop-foss4g/about_data.rst @ 36

.. _about_data:

Partie 5 : à propos de nos données
==================================

Les données utilisées dans ces travaux proatiques sont quatre shapefiles de la ville de New York, et une table attributaire des variables sociodémographiques. Nous les avons charger sous forme de tables PostGIS et nous ajouterons les données  sociédémographiques plus tard.

Cette partie fournit le nombre d'enregistrements et les attributs de chacun de nos ensembles de données. Ces valeurs attributaire et les relation sont essentielles pour nos future analyses.

Pour visualiser la nature de vos tables depuis pgAdmin, cliquez avec le bouton droit sur une table et sélectionnez **Properties**. Vous trouverez un résumé des propriétés de la table, incluant la liste des attributs d'une tables dans l'onglet **Columns**.

nyc_census_blocks
-----------------

Un bloque ressencé est la plus petite entité géographique pour laquelle un ressencement est raporté. Toutes les couches représentant les niveaus suppérieurs (régions, zones de métro, comtés) peuvent être contruit à partir de ces bloques. Nous avons attaché des données démographiques au bloques.

Nombre d'enregistrements : 36592

.. list-table::
   :widths: 20 80 

   * - **blkid**
     - Un code à 15 chiffres qui permet d'identifier de maniÚre unique chaque bloque **block**. Eg: 360050001009000
   * - **popn_total**
     - Nombre total de personnes dans le bloque
   * - **popn_white**
     - Nombre de personne se déclarant comme de couleur blanche
   * - **popn_black**
     - Nombre de personne se déclarant comme de couleur noire
   * - **popn_nativ**
     - Nombre de personne se déclarant comme natif d'amérique du nord
   * - **popn_asian**
     - Nombre de personne se déclarant comme asiatique
   * - **popn_other**
     - Nombre de personne se déclarant comme faisant partie d'une autre catégorie
   * - **hous_total**
     - Nombre de piÚce dans le bloque
   * - **hous_own**
     - Nombre de propriétaires occupant le bloque
   * - **hous_rent**
     - Nombre de locataire occupant le bloque
   * - **boroname**
     - Nom du quartier. Manhattan, The Bronx, Brooklyn, Staten Island, Queens
   * - **the_geom**
     - Polygone représentant les contours d'un bloque

.. figure:: ./screenshots/nyc_census_blocks.png
   
   *Pourcentage de la population quiest de couleur noire* 

.. 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 <http://factfinder.census.gov>`_. 
    
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

.. list-table::
   :widths: 20 80 

   * - **name**
     - Name of the neighborhood
   * - **boroname**
     - Name of the New York borough. Manhattan, The Bronx, Brooklyn, Staten Island, Queens
   * - **the_geom**
     - Polygon boundary of the neighborhood
   
.. figure:: ./screenshots/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

.. list-table::
   :widths: 20 80 

   * - **name**
     - Name of the street
   * - **oneway**
     - Is the street one-way? "yes" = yes, "" = no
   * - **type**
     - Road type. Eg. primary, secondary, residential, motorway
   * - **the_geom**
     - Linear centerline of the street
   
.. figure:: ./screenshots/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

.. list-table::
   :widths: 20 80

   * - **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
   * - **the_geom**
     - Point location of the station

.. figure:: ./screenshots/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. 

.. list-table::
   :widths: 20 80

   * - **tractid**
     - An 11-digit code that uniquely identifies every census **tract**. Eg: 36005000100
   * - **transit_total**
     - Number of workers in the tract
   * - **transit_public**
     - Number of workers in the tract who take public transit
   * - **transit_private**
     - Number of workers in the tract who use private automobiles / motorcycles
   * - **transit_other**
     - Number of workers in the tract who use other forms like walking / biking
   * - **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_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