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GIS Tutorial 1

GIS Tutorial 1. Lecture 5 Spatial Data. Outline. GIS coordinates Map projections Vector data formats US Census geographic files US Census data files Geospatial data sources. Lecture 5. GIS coordinates. Spherical Coordinates. Geographic Coordinate System (GCS)

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GIS Tutorial 1

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  1. GIS Tutorial 1 Lecture 5 Spatial Data
  2. Outline GIS coordinates Map projections Vector data formats US Census geographic files US Census data files Geospatial data sources GIS TUTORIAL 1 - Basic Workbook
  3. Lecture 5 GIS coordinates
  4. Spherical Coordinates GIS TUTORIAL 1 - Basic Workbook Geographic Coordinate System (GCS) Angles of rotation of a radius anchored at Earth’s center Latitude and longitude Used by US Census, other world and federal agencies 4
  5. Latitude and longitude longitude (prime meridian) 0 latitude (equator) 0 GIS TUTORIAL 1 - Basic Workbook 5
  6. RoyalObservatory, Greenwich, England Prime meridian Photo courtesy of Paul Edwin Mastin, January 2011 GIS TUTORIAL 1 - Basic Workbook 6
  7. Marco Zero monument, Macapá, Brazil Equator Photo courtesy of Shan Shi GIS TUTORIAL 1 - Basic Workbook 7
  8. Latitude and longitude Pittsburgh, PA USA 40 -80 GIS TUTORIAL 1 - Basic Workbook Coordinates 8
  9. Lat/Long coordinates GIS TUTORIAL 1 - Basic Workbook Degrees, minutes, and seconds (DMS) 40° 26′ 2″ N latitude -80° 0′ 58″ W longitude Decimal degrees (DD) 1 degree = 60 minutes 1 minute = 60 seconds 40° 26′ 2″ = 40 + (26 / 60) + (2 / 3600) = 40 + .43333 + .00055 = 40.434° 9
  10. Lat/long coordinates GIS TUTORIAL 1 - Basic Workbook Translated to distance World circumference through the poles is 24,859.82 mi, so for latitude: 1° = 24,859.82 / 360 = 69.1 mi 1′ = 24,859.82 / (360 * 60) = 1.15 mi 1″ = 24,859.82 * 5,280 / (360 * 3,600) = 101 ft Length of the equator is 24,901.55 mi 10
  11. GCS example (census tracts) GIS TUTORIAL 1 - Basic Workbook 11
  12. Rectangular coordinates GIS TUTORIAL 1 - Basic Workbook UTM (universal transverse Mercator) US military State plane Local US governments 12
  13. UTM coordinates example GIS TUTORIAL 1 - Basic Workbook Developed by US Army Corps of Engineers (1940s) Covers world, 80°S to 80°N Metric coordinates 60 tuned transverse Mercator projections for longitude zones, 6° wide 13
  14. State plane coordinates GIS TUTORIAL 1 - Basic Workbook Established by the US Coast and Geodetic Survey in the 1930s All positive coordinates in feet or meters Used by local US governments Originally North American Datum (NAD 1927) More recently NAD 1983 and 1983 HARN (High Accuracy Reference Network) 14
  15. State plane zones GIS TUTORIAL 1 - Basic Workbook 125 zones At least one for each state Cannot join zones to make larger regions Follow state and county boundaries Each zone has its own tuned projection Lambert conformal projection for zones with eastwest orientation Transverse Mercator projection for zones with northsouth orientation 15
  16. State plane zones GIS TUTORIAL 1 - Basic Workbook 16
  17. State plane coordinates example GIS TUTORIAL 1 - Basic Workbook State plane NAD 1983, Pennsylvania South, Feet 17
  18. X,y coordinate tips US Census Geographic coordinate system (GCS) City of Pittsburgh State plane coordinate system GIS TUTORIAL 1 - Basic Workbook Always assign coordinates according to the agency 18
  19. X,y coordinate examples US Census Geographic coordinates (GCS) Block groups City of Pittsburgh State plane coordinates Sidewalks GIS TUTORIAL 1 - Basic Workbook 19
  20. Map document tip GIS TUTORIAL 1 - Basic Workbook The first layer added in ArcMap sets the x,y coordinate system for the data frame Additional layers will overlay properly as long as the correct coordinate system is assigned to feature class For example, GCS to US Census files, state plane to local government files Known as .prj files 20
  21. Map document tip GIS TUTORIAL 1 - Basic Workbook Example: Sidewalks added first (state plane), but block groups match even though they are in geographic coordinate system (GCS) projection. 21
  22. Lecture 5 Map projections
  23. Map projections GIS TUTORIAL 1 - Basic Workbook Way to represent the curved surface of the earth on the flat surface of a map Hundreds of map projections Each map projection has advantages and disadvantages: Depends on the scale of the map Depends on map’s purpose Different projections good for small areas, areas with a large east–west extent, or areas with a large north–south extent 23
  24. Map projections Flatten half of a rubber ball? No. Instead, features are projected onto one of three “developable” surfaces. Planar: a map projection resulting from the conceptual projection of the earth onto a tangent or secant plane Cylindrical: a map projection where the earth’s surface is projected onto a tangent or secant cylinder, which is then cut lengthwise and laid flat Conic: a map projection where the earth’s surface is projected onto a tangent or secant cone, which is then cut from apex to base and laid flat http://www.nationalatlas.gov/articles/mapping/a_projections.html#two GIS TUTORIAL 1 - Basic Workbook 24
  25. Conformal projection Example: Mercator projection (1569) used for nautical purposes (constant courses are straight lines) GIS TUTORIAL 1 - Basic Workbook Cylindrical projection Parallels and meridians at right angles Angles and shapes of small objects preserved (at every point, east–west scale same as north–south scale) The size/shape/area of large objects distorted (scale approaches infinity at the poles) Seldom used for world maps 25
  26. Equivalent projection Example: Albers Equal Area standard projection for US Geological Survey, US Census Bureau GIS TUTORIAL 1 - Basic Workbook Conic projection Preserves accurate area Scale and shape are not preserved 26
  27. Compromise projections Example:Robinson projection (1961) good compromise projection for viewing entire world used by Rand McNally and the National Geographic Society GIS TUTORIAL 1 - Basic Workbook Neither equivalent nor conformal Meridians curve gently, avoiding extremes. Doesn’t preserve properties, but “looks right” 27
  28. When projection is important Small-scale maps Comparing shapes, areas, distances, or directions of map features Natural appearance desired New York New York Los Angeles Los Angeles Los Angeles Projection: Albers Equal AreaDistance: 2,455.03 miles Projection: MercatorDistance: 3,124.67 miles Actual distance: 2,451 miles GIS TUTORIAL 1 - Basic Workbook 28
  29. When projection is not important Many business, policy, and management applications On large-scale maps Error is negligible GIS TUTORIAL 1 - Basic Workbook 29
  30. Lecture 5 Vector data formats GIS TUTORIAL 1 - Basic Workbook
  31. ArcInfo coverages GIS TUTORIAL 1 - Basic Workbook Created using Esri ArcInfo software Older format Set of files within a folder or directory called a workspace Files represent different types of topology or feature types
  32. Shapefiles GIS TUTORIAL 1 - Basic Workbook ArcView native format Minimum files .shp–stores feature geometry .shx–stores index of features .dbf–stores attribute data Additional files .prj–projection data .xml–metadata .sbn and .sbx–store additional indices
  33. CAD drawings GIS TUTORIAL 1 - Basic Workbook CAD software Autodesk, AutoCAD (.dwg) Bentley, Microstation (.dgn, .dxf) Often used by engineering companies Better digitizing precision
  34. CAD drawings GIS TUTORIAL 1 - Basic Workbook
  35. Lecture 5 US Census geographic files
  36. Census TIGER/Line files GIS TUTORIAL 1 - Basic Workbook http://www.census.gov/geo/www/tiger/ Topologically Integrated Geographic Encoding and Referencing files US Census Bureau product for digital mapping of the United States TIGER maps available for the entire United States and its possessions, including roads and streets, railroads, rivers, lakes, political boundaries, and census statistical boundaries 36
  37. Example census geographies GIS TUTORIAL 1 - Basic Workbook 37
  38. TIGER census tracts GIS TUTORIAL 1 - Basic Workbook Between 1,000 and 8,000 people (in general) 1,700 housing units or 4,000 people Homogeneous population characteristics (economic status and living conditions) Normally follow visible features May follow governmental unit boundaries and other invisible features
  39. State tracts (2010) GIS TUTORIAL 1 - Basic Workbook
  40. County tracts (2000 and 2010) GIS TUTORIAL 1 - Basic Workbook
  41. City tracts (2000 and 2010) GIS TUTORIAL 1 - Basic Workbook
  42. City block groups (2000 and 2010) Subdivisions of a census tract 400 housing units, with a min. of 250 and a max. of 550 Follow clearly visible features (roads, rivers, and railroads) GIS TUTORIAL 1 - Basic Workbook
  43. Census blocks Smallest geographic areas for which the Census Bureau collects and tabulates decennial census information Block boundaries visible (street, road, stream, shoreline, etc.) or invisible (county line, city limit, property line, etc.) GIS TUTORIAL 1 - Basic Workbook
  44. Lecture 5 US Census data files
  45. Decennial census data GIS TUTORIAL 1 - Basic Workbook Years 2000 and 2010 Summary File 1 (SF 1) Short form, entire population Population Age Sex Race Families Households Housing units Tracts, block groups, blocks
  46. Decennial census data GIS TUTORIAL 1 - Basic Workbook Year 2000 Summary File 3 (SF 3) Long form, 1 in 6 households, random Income, poverty Educational attainment Citizenship Employment, workplace, disability Transportation, travel time to work Detailed housing attributes, housing value, residency five years previous Languages spoken, ancestry Tracts, block groups, NOT blocks
  47. Replaces long-form questionnaire and SF3 data Randomly selects about 3 million addresses each year to participate Has rolling, 1-, 3-, and 5-year estimates and 90% confidence intervals Add and subtract Margin of Error (MOE) to/from Estimate to get the confidence interval American Community Survey (ACS) GIS TUTORIAL 1 - Basic Workbook 47
  48. Age Sex Race Family and relationships Income and benefits Health insurance Education Veteran status Disabilities Where you work and how you get there Where you live and how much you pay for certain essentials ACS Data GIS TUTORIAL 1 - Basic Workbook
  49. ACS 1-year estimates GIS TUTORIAL 1 - Basic Workbook Most current Data with populations 65,000+ Smallest sample size Less reliable than 3–5 year Best used when currency is more important than precision, or when analyzing large populations Not available for tracts or block groups
  50. ACS 3-year estimates GIS TUTORIAL 1 - Basic Workbook Data with populations 20,000+ Larger sample size than 1-year More reliable than 1-year but less reliable than 5-year Best used when analyzing smaller populations or geographies not available for 1-year estimates Not available for tracts or block groups
  51. ACS 5-year estimates GIS TUTORIAL 1 - Basic Workbook Data for all areas (tracts and block groups) Largest sample size Most reliable but least current Best used when analyzing small populations, or when precision is more important than currency 2005–2009, 2006–2010, etc. Note: 2006–2010 only available for county, city, town, place, American Indian Area, Alaska Native Area, Hawaiian Home Land, and tracts. Block group estimates are available only in the ACS Summary File.
  52. Downloading block group data GIS TUTORIAL 1 - Basic Workbook http://www.census.gov/acs/www/data_documentation/summary_file/ Find the tables of interest and their sequence number in the "Sequenced Number and Table Number" spreadsheet (http://www2.census.gov/ acs2010_5yr/summaryfile/) Download the sequences that contain those tables
  53. Other census data GIS TUTORIAL 1 - Basic Workbook Economic census Population estimates Annual economic surveys DataFerret http://dataferrett.census.gov/
  54. Lecture 5 Geospatial data sources
  55. Spatial data infrastructure GIS TUTORIAL 1 - Basic Workbook Federal Geographic Data Committee (FGDC) This nationwide data publishing effort known as National Spatial Data Infrastructure (NSDI). Established by presidential order Responsible for standards, policies, web portals FGDC activities are administered through the FGDC Secretariat, hosted by the US Geological Survey
  56. Spatial data packaging GIS TUTORIAL 1 - Basic Workbook Metadata Documentation enabling intelligent use and interpretation Data contents Provided by geographic area (political, statistical, tile) or seamlessly (with extraction by area) Quality of geographic features Vector maps are generalized for small-scale maps Raster maps vary by pixel size (30m to a few inches) and color depth 8 bits to 24 bits per pixel Coordinate system File format Download or web service
  57. Classification of map layers GIS TUTORIAL 1 - Basic Workbook Earth as a system Living things are on, under, or above the Earth’s surface They depend on the Earth and its environment for life and well-being They are organized in political, social, territorial, and other arrangements Map layers Physical features: Earth’s surface and subsurface Environmental features: atmosphere, climate, and weather Living thing populations: people, animals, plants, and microbes Organizational features: political, legal, administrative, and ecosystem
  58. National Map orthoimagery GIS TUTORIAL 1 - Basic Workbook http://nationalmap.gov/viewer.html Replacing the digital orthophoto quadrangles High-resolution, seamless images in UTM coordinates Rectified to remove distortions 1m resolution with 0.5 m or 1 ft in urban areas, natural color
  59. National Elevation Data (NED) Hillshade NED map for Rockville, MD GIS TUTORIAL 1 - Basic Workbook http://ned.usgs.gov/ Replaces the digital elevation model (DEM) Seamless raster map with 30m resolution for nation and 10m or better in some areas
  60. Land cover GIS TUTORIAL 1 - Basic Workbook http://nationalmap.gov/viewer.html/ Natural and man-made surface features Collected from satellites in 1992, 2001, and 2006
  61. National Hydrography Dataset GIS TUTORIAL 1 - Basic Workbook http://nhd.usgs.gov/ Water bodies, lines, and points Identifies segments (reaches) with network coding (flow and direction)
  62. USGS national water datasets GIS TUTORIAL 1 - Basic Workbook http://waterdata.usgs.gov/nwis/rt Streamflow conditions 5,000 stream gages with telemetry transmits depth Program estimates flow rate
  63. Example geospatial sources GIS TUTORIAL 1 - Basic Workbook Government websites (examples) http://data.gov/ http://www.geoplatform.gov/home/ http://nationalatlas.gov/ http://nces.ed.gov/ccd/ - National Center for Education Statistics Universities State clearinghouses Local GIS departments Libraries For example, online business databases
  64. Example geospatial sources GIS TUTORIAL 1 - Basic Workbook Commercial resources (Esri, Google, engineering companies, etc.) Historic GIS websites http://www.nhgis.org/ http://www.aag.org/cs/projects_and_programs/historical_gis_clearinghouse http://peoplemaps.esri.com/pittviewer/
  65. Summary GIS coordinates Map projections Vector data formats US Census geographic files US Census data files Geospatial data sources GIS TUTORIAL 1 - Basic Workbook
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