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“Jump Start” GIS

“Jump Start” GIS. Where to Find GIS Data. Agenda. Briefly introduce the following topics: GIS data models Projections and datums Metadata Discuss where to get GIS data Brief demo on how to get data into your GIS. Data Models: Raster and Vector. Vector Data Model.

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“Jump Start” GIS

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  1. “Jump Start” GIS Where to Find GIS Data

  2. Agenda • Briefly introduce the following topics: • GIS data models • Projections and datums • Metadata • Discuss where to get GIS data • Brief demo on how to get data into your GIS

  3. Data Models: Raster and Vector

  4. Vector Data Model • point: primary data object • single x-y coordinate pair • lines: formed by joining two or more points • at least two x-y coordinate pairs • nodes: points composing lines • polygons: formed by joining together multiple lines • at least three x-y coordinate pairs

  5. Raster Data Model • cell: primary data object • also called “pixel” -- usually for image data • represented by x-y coordinate and a cell size • cells are regularly spaced to cover entire data area • called a tessellation

  6. Map Projections • 3-dimensional Earth cannot be accurately portrayed on a flat map • ‘Flattening’ Earth onto a map causes distortion of one or more properties • Distance • Direction • Shape (conformality) • Area • A map can be ‘projected’ to preserve a desired property, but usually at the expense of the others • USGS provides a concise, yet detailed, poster of many projections at the following URL for those interested in learning more http://erg.usgs.gov/isb/pubs/MapProjections/projections.html

  7. Datums • What is a datum? • Geodetic control network , or triangulated network of known locations used as a mapping framework • North American Datum of 1927 (NAD27) was the original control network for US and is used in USGS topographic maps. • NAD83 is a more accurate datum that has replaced NAD27 as the new standard for US maps • World Geodetic Survey 1984 (WGS84) is used by the Global Positioning System and has been adopted as the global standard • WGS84 and NAD83 are practically equal, however the difference between NAD83 and NAD27 can be as much as 200 meters in the US

  8. Metadata • Definition ~ “data about data” • Contains information about data such as who created it, contact information, projection information, how to download, etc. • Serves as a means for data ‘authors’ to communicate with users • Very important – should not be overlooked…

  9. Data Sources…

  10. ESRI Data CDs • What’s on them? • Imagery • StreetMap USA • Background maps of world and US • E.g. Rivers and lakes, political boundaries, national parks, etc. • Where can I get them? • As part of the ArcGIS Media Kit (that comes with your software) • In the RTP Library • We can make additional copies

  11. ESRI World CD

  12. ESRI United States CD

  13. Online Sources - General • USDA Geospatial Data Gateway • http://datagateway.nrcs.usda.gov/ • An excellent source of geospatial data, including imagery, agriculture and hydrological data • Geodata.gov US Maps and Data • http://gos2.geodata.gov/wps/portal/gos • “Your one stop for finding and using geographic data” • USGS Seamless Data Distribution System • http://seamless.usgs.gov/ • Another comprehensive data source, including elevation and landcover • The National Atlas • http://nationalatlas.gov/ • Self-proclaimed “single best Federal source for national maps and information on the web.” Good comprehensive site with a wide variety of data, including demographic data • United Nations Environment Programme (UNEP) GEO Data Portal • http://geodata.grid.unep.ch/ • A good source for international geospatial data

  14. Online Sources - Imagery • UMD Global Landcover Facility • http://glcf.umiacs.umd.edu/index.shtml • Provides access to a host of free satellite imagery • USGS Earth Resources Observation and Science (EROS) • http://mapping.usgs.gov/ • Provides access to free satellite imagery for Federal users. Registration required

  15. Web Services • The Geography Network • http://www.geographynetwork.com/ • An extensive network of various types of geospatial data, including downloadable data and web services • US Department of Health and Human Services • http://datawarehouse.hrsa.gov • Offers a broad range of health-related geospatial data • US-EPA ArcIMS Image and Feature Services • http://geodata.epa.gov • Provides access to ArcIMS web services created by EPA • EPA Intranet Geodata Service (INGEO) • http://intramap33.rtpnc.epa.gov • Intranet access to 2005 GDT/Teleatlas Street Data for entire United States

  16. National GIS Repository • UNC-Chapel Hill GIS Library • http://www.lib.unc.edu/reference/gis/onlinedata.html • Contains a wealth of information about geospatial data, including links to data from all levels of government • Contact info for GIS Librarian: Amanda Henley Amanda.henley@unc.edu 919-962-1151

  17. Demo

  18. Next Presentation Making Maps with GIS Thursday, April 13 11:30 – 12:30 C113

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