Human/ Physical GIS and Census Data Flashcards
What does TIGER stand for?
Topologically Integrated Geographic Encoding and Referencing
What do TIGER files provide?
- census geography polygons and linear and point feature data
- to allow mapping the 1990 through 2010 censuses and placing them in context.
What is the objective of TIGER?
Objective is to map the census for each decade since 1990. Provides a wide range of scales of geographic aggregation following the census itself.
What levels is TIGER data available at?
Available at several levels from national – state – county with different internal identifiers to tie to the census enumeration units
What scale is TIGER best for?
Data are spatially accurate to 1:100,000 scale (NMAS of 167’), so good for moderate to smaller scale representations. Can be argued though that the census enumeration units are really thematic data bases - not really reference oriented to begin with. Accuracy also applies to features though!
How are feature types in the TIGER shapefiles coded?
Feature types in the Shapefiles are coded by the Master Address File / TIGER Feature Class Codes (MTFCC) which are made up of a letter and 4 digit number.
Feature data are all found in the “All Lines” shapefile at the county level. Some state level data are also available in the feature sets.
National and State TIGER files have the data units aggregated from _______ units to __________, and some for the entire US.
Is the scale still the same?
What are enumeration units downloaded at?
These files have the data units aggregated from county units up to states and some for the entire US.
All are still the same scale (1:100,000) so the detail levels are high for these larger units.
State or national level since 2011.
What are TIGER features and what are they included for?
What are the 7 TIGER features?
Tiger features are included for analytical purposes, and because many of the census unit geography edges use these features. There are a number of types (not all will appear in every county):
Physical Landmarks – mountain peaks, quarries (C)
Hydrology (H) – streams, ponds etc.
Human Landmarks – apartment, campground (K)
Linear Features – pipelines, power lines (L)
Railroads (R) – main line tracks
Roads and Highways (S) – coded by quality
What is Census geography?
The Census collects data from individual people and releases data about those people in aggregates of variable sizes.
A knowledge of the spatial units of data available is very helpful in research with GIS. As units get smaller, with fewer people in them, fewer variables are disclosed.
How do block, block groups, and census tracts relate to each other?
Census tracts are in block groups, which are in blocks.
Look at slide 16 for illustration (it’ll make it easier to visualize)
What is are blocks?
Smallest units of data tabulation Cover the entire nation Do not cross census tracts or counties Generally bounded by visible features and legal boundaries Size: average about 100 people US: 8,000,000+ Mcty: 3,560 blocks
What is the official definition for blocks? How many blocks are delineated for Census 2000? How have blocks been renumbered?
A block is defined as an area bounded on all sides by visible and/or invisible features shown on a map prepared by the U.S. Census Bureau. A block is the smallest geographic entity for which the Census Bureau tabulates decennial census data.
There are about 8,200,000 blocks delineated for Census 2000.
There has been a complete renumbering of blocks across the U.S. One other major change is that the numbering has gone from a three-digit system to a four-digit system. Water bodies were also assigned block numbers in Census 2000 for the first time.
What are block groups?
Groups of blocks sharing the same first digit
Smallest areas for which sample data (ACS) are made available
Size: optimally 1,500 people, range between 300 to 3,000
US: 211,000+
Mcty: 58 block groups
What is the official definition for block groups?
Block groups are the ________ entity for which the US Census Bureau tabulates sample data from decinnial census.m
A statistical subdivision of a census tract (or, prior to Census 2000, a block numbering area), a block group consists of a cluster of census blocks having the same first digit of their identifying numbers within that tract.
For example, for Census 2000, BG 3 within a census tract includes all blocks numbered from 3000 to 3999. (A few BGs consist of a single block.) BGs generally contain between 300 and 3,000 people, with an optimum size of 1,500 people.
Lowest-level
What are census tracts?
Groups of Block Groups.
Relatively homogenous population characteristics
65,000 Census tracts across U.S.
Size: optimally 4,000 people, range between 1,000 and 8,000
US: 66,000+
Mcty: 16 tracts
What is the official definition for census tracts?
Census tracts are small, relatively permanent statistical subdivisions of a county or a statistically equivalent entity. Designed to be relatively homogeneous units with respect to population characteristics, economic status, and living conditions at the time they are established, census tracts generally contain between 1,000 and 8,000 people, with an optimum size of 4,000 people. Census tract boundaries are delineated with the intention of being stable over many decades, so they generally follow relatively permanent visible features. However, they may follow governmental unit boundaries and other invisible features in some instances; the boundary of a state or county is always a census tract boundary.
Census tracts are usually identified by a six-digit number composed of a four-digit basic number and a two-digit numeric suffix; for example, 8001.07. This suffix (.07) indicates that the original tract, tract 8001, was split possibly into seven pieces as a result of population growth. In some maps the census tract may be represented by a single digit number - in those cases the three leading zeroes were omitted for simplification. However, all census tracts have 6 digits (first four and the last two after the decimal).
In 1990 and previous censuses, the Census Bureau created tract-like geographic units, called Block Numbering Areas or BNAs, outside of metropolitan areas. BNAs were discontinued for Census 2000; instead, one or more census tracts were identified for every county and statistically equivalent entity.
Census tracts are usually delineated for data presentation purposes by a local group of census data users or the geographic staff of a regional census center in accordance with U.S. Census Bureau guidelines.
What are county subdivisions?
In many states these are local political units such as townships. In others they are census derived.
Do NOT have to follow minimum or maximum population guidelines, nor fit hierarchically with other census geography levels (eg. Tracts shown)
US: 35,000+
Mcty: 7
What is the official definition of county subdivisions?
A minor civil division (MCD) is the the primary governmental or administrative division of a county or statistically equivalent entity in many states and statistically equivalent entities. A minor civil division is created to govern or administer an area rather than a specific population.(ex. Town, Township, District) The U.S. Census Bureau recognizes minor civil divisions in 28 states, the District of Columbia, Puerto Rico, and the Island Areas.
A census county division (CCD) is a statistical subdivision of a county, delineated by the U.S. Census Bureau in cooperation with state and local government officials for data presentation purposes. A census county division usually represents one or more communities, trading centers or, in some instances, major land uses. The Census Bureau has established census county divisions in states that do not have minor civil divisions suitable for data presentation.
Minor civil divisions and census county divisions together cover the entire country and provide a standard level of geography below the county. Minor civil divisions are more common in the East, while census county divisions are more common in the West.
What are places?
Incorporated Places – towns and cities
Census Designated Places – “locally agreed upon” places and unincorporated “towns”
Note that these are not contiguous and do not fit in the hierarchy of blocks, block groups, and tracts.
US: 25,000+
Mcty: 10 places
What is the official definition of places?
There are two kinds of places in Census Bureau terminology: incorporated places and Census Designated Places (CDPs).
A place is a concentration of population legally bounded as an incorporated place. A CDP is delineated for statistical purposes as a census designated place (in Puerto Rico, a comunidad or zona urbana). These are created for the purpose of presenting census data for an area with a concentration of population, housing, and commercial structures that is identifiable by name, but is not within an incorporated place. For Census 2000, for the first time, CDPs did not need to meet a minimum population threshold to qualify for tabulation of census data.
As you can see in this map taken from the American FactFinder, the boundaries of places - either incorporated or CDPs - do NOT necessarily correspond to census tracts, block groups or MCDs.
Speaker note: CDP boundaries, which usually coincide with visible features or the boundary of an adjacent incorporated place or other legal entity boundary, have no legal status, nor do these places have officials elected to serve traditional municipal functions. CDPs usually are delineated in cooperation with state, Puerto Rico, Island Area, local, and tribal officials based on U.S. Census Bureau guidelines.
What are counties?
Counties in 48 States Parishes in Louisiana Cities and Boroughs in Alaska Independent Cities in 4 States National File – does not include accurate coastlines US: 3,141
What is the official definition of counties?
Counties are the primary subdivision of most states. A number of geographic entities are not legally designated as a county, but are recognized by the U.S. Census Bureau as equivalent to a county for data presentation purposes.
What are congressional districts?
National Files only.
US: 441
Virginia: 11
