1. Dept. of Geography - Computing Orientation - Fall 1999 GIS Data Sources

2. U.S. Census Data & TIGER/Line Files National topographic/base data Most countries have federal agencies charged with mapping national resources & infrastructure… e.g., United States Geological Survey – established 1879 –many European countries far earlier also previously created by colonial powers for colonies these topographic “base” maps  valuable spatial data source finding and getting access can be difficult contact the national agencies good list: http://maplib.clarku.edu/offices/maplibrary/links.htm resellers, e.g. Omni Resources (nearby, in Burlington, NC) – www.omnimap.com www.omnimap.com

3. U.S. Census Data & TIGER/Line Files National topographic/base data “Topographic map” name refers to information (contour lines) about terrain/elevation = topography “topographic maps” generally contain much more than just elevation info Topographic base map info  increasingly digital many developed countries are well into the conversion process U.S. nearly complete less-developed countries much less so even with digital source data… still need to be able to gain access, import data format, etc…

4. U.S. Census Data & TIGER/Line Files National Spatial Data Infrastructure (NSDI) Coordinated by Federal Geographic Data Committee FGDC formalized in 1994 -- oversee production of 100’s of federal spatial data products 17 federal agencies + state, county, local, & tribal governments Create standards for content & format of digital spatial data Spatial Data Transfer Standard (SDTS) catalog of possible spatial features, defines spatial terms profiles: topological vector profile, raster profile, point profile metadata Content-specific standards, e.g. cadastral (property mapping) wetlands & deep-water habitats vegetation classification soils mapping digital orthoimagery -- still very much a work in progress… will it be comprehensively adopted??? FGDC also required to provide data clearinghouse http://www.fgdc.gov/clearinghouse Good spot to find US geographic data

5. U.S. Census Data & TIGER/Line Files USGS topographic maps Complete coverage of the U.S. (not at all scales) Large-scale - 1:24,000 occasional maps at 1:25,000 (metric) “7.5-minute quadrangle” map sheets -- 54,000 to cover contiguous U.S. and Hawaii Alaska only available as 1:63,360 maps include… roads, railroads, hydrography, cemeteries, churches, schools, etc… plus contour lines Also 1:100,000 and 1:250,000 topographic map series but smaller the scale  less detail Digital versions of USGS topographic maps 1:24,000 (large scale) + 1:63,360 for Alaska 1:100,000 (intermediate scale) 1:2,000,000 (small scale)

6. U.S. Census Data & TIGER/Line Files USGS Data – Digital Raster Graphics (DRG) Raster images of standard topograhpic maps Scanned and georeferenced include map collar Pixel attributes…? color value  data?

7. U.S. Census Data & TIGER/Line Files USGS – Digital Line Graphs (DLG) 1:24:000 scale reproduces 7.5-min quads: Boundaries (state, county, city, national parks/preserves) Hydrography Transportation (roads, streets, railroads) Transmission (pipelines and powerlines) Elevation contours and spot elevation values Basic surface cover -- e.g., vegetation type, rock, urban, etc... Human-made & cultural features Geodetic survey control points & markers 1:100,000 & 1:2,000,000 fewer feature types included Image of USGS 1:24,000 West Rapid City (South Dakota) DLG quadrangle. Hydrography shown in cyan, roads in red, pipelines/transmission lines in green, & railroads in blue. (GIF image from USGS.)

8. U.S. Census Data & TIGER/Line Files USGS – Digital Elevation Models (DEM) Raster-format elevation data Elevation samples at regularly- spaced intervals Large scale: 1:24,000 7.5x7.5-minute units spatial resolution = 30x30meters Intermediate scale: 1:100,000 30x30-minute units Small scale: 1:250,000 1x1-degree units

9. U.S. Census Data & TIGER/Line Files Spatial data on the web… FGDC required to provide data clearinghouse http://www.fgdc.gov/clearinghouse Good spot to find US geographic data Other online data resources www.gisdatadepot.com http://www.esri.com/data/online Meta-lists, e.g. Digital Elevation Data Catalog www.geo.ed.ac.uk/home/ded.html State clearinghouses e.g. Pennsylvania Spatial Data Access www.pasda.psu.edu/access/index.shtml e.g. North Carolina Center for Geographic Information and Analysis www.cgia.state.nc.us cost-recovery… Multinational efforts… Global Spatial Data Initiative www.gsdi.org

10. U.S. Census Data & TIGER/Line Files Data Sources Census Bureau : Charged with the Constitutional responsibility of carrying out the decennial census o Census of Population and Housing Very large mapping component involved in undertaking a U.S. national census! U.S. Census Data & TIGER/Line Files

11. U.S. Census Data The U.S. Census acquires data from households about: Demographic info Race Population Disabilities Migration Economic info Living quarters Occupation Income Social info Languages spoken School enrollment Family structure in the home Marital status Ancestry Foreign-born population

12. U.S. Census Data & TIGER/Line Files  Census data collected by household  Geographic location of the household must be known  To find household to deliver questionnaire  To relate the questionnaire to a place U.S. Census Data & TIGER/Line Files

13. TIGER/Line files: The “geography” of the census Topologically Integrated Geographic Encoding & Referencing Examples of layers of this massive dataset: streets Address ranges of households landmarks for census-taking County/city/block boundaries U.S. Census Data & TIGER/Line Files

14. TIGER designed to: support pre-census functions in preparation for Census of Population and Housing support census-taking efforts evaluate success of the Census provide geographic framework for analysis of Census data U.S. Census Data & TIGER/Line Files

15. Before TIGER/Line TIGER/Line files used in the 1990 and 2000 census Will be used in the future by the Census Bureau Before TIGER/Line files was GBF/DIME system GBF/DIME Created in 1967 Used for the 1970 and 1980 censuses

16. U.S. Census Data & TIGER/Line Files Enumeration units for TIGER/LINE Files Privacy issue Data not available to public by HH Data aggregated to larger geographic units Prevents breaches of privacy Allows for useful geographic data summaries

17. U.S. Census Data & TIGER/Line Files Hierarchical Organization Subdivisional Portrays the internal divisions of a hierarchy Example: Regions of North Carolina

18. U.S. Census Data & TIGER/Line Files hierarchical tabulation systems, e.g.: USA Region Division State County Tract Block Group Block 2000 Census tallies for entire US: 65,443 tracts 208,790 block groups 8,205,582 blocks for NC: 1,563 tracts 5,271 block groups 232,403 blocks Census geographic hierarchy

19. U.S. Census Data & TIGER/Line Files TIGER/LINE Files Supporting geography roads/streets/highways basic hydrography point & area landmarks etc...

20. U.S. Census Data & TIGER/Line Files TIGER area (polygon) & landmark data Point and polygon landmarks Census geography (tracts, blocks, etc.) used for reporting Census data ID linkage from polygons in TIGER/Line data to Census attribute data

21. U.S. Census Data & TIGER/Line Files TIGER line and address data Roads attributes include basic road type, address ranges

22. U.S. Census Data & TIGER/Line Files TIGER address data address ranges: street address numbers at beginning and ending of arc/line in database allows address geocoding  match data with address to a spatial location using an interpolated estimate data use implication: explosion of analysis and data integration capabilities extremely large (and growing) amount of data tied to addresses problem: still some incomplete address range data, esp. in rural areas

23. U.S. Census Data & TIGER/Line Files Link to Census data Census attribute data - Summary data files Link to Census geographic entities in TIGER/Line files using unique Census geography IDs  Lets us merge a tremendously rich source of detailed socioeconomic data (Census) with a comprehensive geography for the entire country… Orange County, NC block groups w/ median income data (darker green = higher income)

24. U.S. Census Data & TIGER/Line Files Errror/accuracy problems… Spatial error from a variety of sources Lines digitized from 1:100,000 scale maps errors in source DIME files updates from many agencies and localities across the U.S. little or no quality control! and more… Official statement: meets National Map Accuracy Standards for 100,000-scale data = +/- 167 feet But… is a high-level of spatial accuracy in TIGER necessary for Census purposes? Another problem: new development after updating  can never keep up…

25. U.S. Census Data & TIGER/Line Files Cost of Census 2000 Products InternetFree CD-ROMs$50 DVDs$60 TIGER/Line files and all kinds of Census data products at http://www.census.gov/