Hui Hu Ph.D.
Department of Epidemiology
College of Public Health and Health Professions & College of Medicine
March 19, 2018
Introduction to Spatial Data
Data Models
A geographic data model is a structure for organizing geospatial data so that it can be easily stored and retrieved.
Geographic coordinates
Tabular attributes
Vector Model
- points, lines, polygons
Raster Model
- exhaustive regular or irregular partitioning of space
Points
Lines
.shp - the file that stores the geometry of the feature
.shx - the file that stores the index of the feature geometry
.dbf - the dBASE file that stores the attribute information
.prj - the file that defines the shapefile's projection
.html, .htm, .xml - the files that usually contains metadata
.sbn and .sbx - store additional indices
3D sphere
Geographic Coordinate System
2D flat
Projected Coordiate System
Common Local Datum: North American Datum (NAD)
Common Global Datum: World Geodetic System (WGS)
The systematic rendering of a graticule on a flat map surface
Converting a sphere to a flat surface results in distortion
nyc_census_blocks
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
Number of records: 36592
nyc_neighborhoods
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
Number of records: 129
New York has a rich history of neighborhood names and extent
nyc_streets
name Name of the street
oneway Is the street one-way? “yes” = yes, “” = no
type Road type (primary, secondary, residential, motorway)
geom Linear centerline of the street
Number of records: 19091
nyc_subway_stations
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
Number of records: 491