GIS Lecture 5: Spatial Data GIS 1
Outline Vector Data Formats Raster Data Formats Map Projections Coordinate Systems US Census geographic files US Census data files GIS Data Sources GIS 2
Vector Data Formats GIS 3
GIS Data Sets Geodatabases (Tutorial 4) ArcView Shapefiles CAD Files Aerial Photos Event Files GIS 4
Shapefiles 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 GIS 5
CAD Drawings CAD Software Autodesk, AutoCAD (.dwg) Bentley, Microstation (.dgn,.dxf) Often used by engineering firms Better precision GIS 6
Event Files Data table that includes map coordinates (such as latitude and longitude) GIS 7
Event Files GIS 8
Exporting Event Files Event Files are not point features Export to shapefile GIS 9
Raster Data Formats GIS 10
Raster Data Formats TIFF -.tif file extension -Very high quality images -File sizes are large JPEG -.jpg file extension -for images that have a lot of color variations -Uses file compression for smaller file sizes GIS 11
Additional Notes Raster layers can portray only one attribute a color for a picture Raster file sizes can be enormous Use aerial photographs to create vector-based map layers for physical features GIS 12
Layer and map packages Map package (.mpk) Full contents of map document Map properties Data frames All layers and data Layer package (.lpk) Full contents of a single layer Includes layer's data May also apply to group layer GIS 13
Map Projections GIS 14
Map Projections and Distortion Mathematical transformation that behaves as if it were projecting features of the world onto one of three surfaces: a plane, cone, or cylinder GIS 15
When Projection Is Important Measurements used to make important decisions Comparing shapes, areas, distances, or directions of map features Feature and image themes are aligned New York New York Los Angeles Los Angeles Projection: Mercator Distance: 3,124.67 miles Actual distance: 2,451 miles Projection: Albers Equal Area Distance: 2,455.03 miles video clip GIS 16
When Projection Is Not Important Business applications Not of critical importance Concerned with the relative location of different features On large scale maps - street maps Distortion may be negligible Map covers only a small part of the Earth's surface. GIS 17
Coordinate Systems GIS 18
Projection vs. Coordinate System Projection = the method used for flattening the paper on the spherical earth Coordinate System = the method for referencing specific locations - on a sphere (Geographic Coordinates) - on that flattened paper (Rectangular Coord) GIS 19
Geographic Coordinates Geographic Coordinate System (GCS) Spherical coordinates Un-Projected Angles of rotation of a radius anchored at earth s center Latitude and Longitude - Census Bureau TIGER files GIS 20
Latitude and Longitude Longitude (Meridians) Latitude (Parallels) GIS 21
Latitude and Longitude 0 Longitude (prime meridian) 0 Latitude (equator) GIS 22
Latitude and Longitude Coordinates Pittsburgh, PA USA 40 26 2 N latitude -80 0 58 W longitude 40-80 GIS 23
Rectangular Coordinates Used for locating an intersection on a flat sheet of paper Cartesian Coordinates (X,Y) Y X<0 Y>0 X>0 Y>0 (0,0) X X<0 Y<0 X>0 Y<0 GIS 24
State Plane Coordinates Used by local US Governments All positive coordinates in feet GIS 25
State Plane Coordinates Zones 125 zones, following state and county boundaries At least one for each state GIS 26
City of Pittsburgh as Geographic Coordinates GIS 27
City of Pittsburgh as State Plane Coordinates GIS 28
Universal Transverse Mercator (UTM) Coordinate system used by U.S. Military Covers entire world Metric coordinates GIS 29
How do I know what my data is? GIS 30
US CENSUS GEOGRAPHIC FILES GIS 31
Census TIGER/Line files 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 GIS 32
Example census geographies GIS 33
TIGER census tracts 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 34 GIS 34
State tracts (2010) 35 GIS 35
County tracts (2000 and 2010) 36 GIS 36
City tracts (2000 and 2010) 37 GIS 37
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) 38 GIS 38
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.) 39 GIS 39
US CENSUS DATA FILES GIS 40
Decennial census data 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 41 GIS 41
Decennial census data 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 42 GIS 42
American Community Survey (ACS) 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 GIS 43
ACS Data 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 44 GIS 44
ACS 1-year estimates 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 45 GIS 45
ACS 3-year estimates 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 46 GIS 46
ACS 5-year estimates 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. 47 GIS 47
Downloading block group data 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 48 GIS 48
U.S. Census Data Tables http://factfinder2.census.gov SF-1 vs ACS (American Community Survey) GIS 49
GIS Data Sources GIS 50
Data Sources U.S. Census - streets (TIGER/line file) - Tracts, Blk Groups, Blocks (polygons) ESRI website -ArcGIS.com - ESRI Data & Maps GIS websites - LA County GIS Data Portal GIS 51
ESRI data online ArcGIS Online: http://www.arcgis.com/home/ Ready to use data and basemaps Esri Data page: http://www.esri.com/data/find-data.html Imagery, Streets, Shaded Relief, Topographic services Demographics, Consumer Spending, Business, and Marketplace applications and service GIS 52
ESRI data Data vs. Map Services - Map Services can be used for background to your map, but they cannot be edited or used for analysis. - You will need actual Data for the analysis portion of your project. GIS 53
ArcGIS Online http://www.arcgis.com GIS 54
Other Sources see GIS Resources List on Barry s website http://www.data.gov USGS and other government sources http://data.geocomm.com http://nationalmap.gov/viewer.html http://gis.fema.gov/datafeeds.html University websites (http://gis.harvard.edu) States, counties, cities http://egis3.lacounty.gov/dataportal/ Internet Searches -type GIS data download or layer package -add the name of the state, county, or city to the search GIS 55
Summary Vector Data Formats Raster Data Formats Map Projections Coordinate Systems US Census geographic files US Census data files GIS Data Sources GIS 56