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Chapter 2 Objectives

Introduction to ArcGIS for Environmental Scientists Module 1 – Data Visualization Chapter 2 – Data Formats and Sources. Chapter 2 Objectives. Basic information about different data formats Managing spatial data Where to find spatial data. Vector Data. Points (cities, monitoring stations)

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Chapter 2 Objectives

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  1. Introduction to ArcGIS forEnvironmental ScientistsModule 1 – Data VisualizationChapter 2 – Data Formats and Sources

  2. Chapter 2 Objectives • Basic information about different data formats • Managing spatial data • Where to find spatial data

  3. Vector Data • Points (cities, monitoring stations) • Lines (roads, rivers) • Polygons (political or natural boundaries) • Stored as X,Y coordinates • Each feature has one or more attributes associated with it

  4. Raster Data • Imagery – satellite, digital aerial photos • Land-cover, elevation, and many others • Stored as a rectangular matrix of square cells • Resolution defines the size of the cell • Each cell usually has a single value associated with it • Values can be integer or floating point

  5. Raster shown at 10 and 30 meter resolutions Raster/Vector Comparison Points Lines

  6. Raster/Vector Comparison Polygon converted to 30 meter raster Polygon converted to 10 meter raster

  7. Coverages • Oldest format, uncommon today • Stored in multiple directories • Can hold multiple feature types • Attributes stored in INFO table(s) • Moving, copying or renaming coverages in Windows Explorer will almost certainly corrupt your data • When exported, stored in .e00 file (called an interchange file) • Cannot be edited in ArcGIS Desktop

  8. Shapefiles In ArcCatalog: • Most common format • Consists of multiple files, must have at least three - .shp, .shx, and .dbf • Can only hold a single feature type • Type can be identified by icon • Attributes stored in dBase table • Can be edited in ArcGIS Desktop In Windows Explorer:

  9. Geodatabases • Newest format, becoming more common • Container for feature classes (can be different geometries), rasters, stand-alone tables • Spatial and attribute information stored in the same database • Fewer size limitations • Faster drawing • Can be edited in ArcGIS Desktop

  10. The Default Geodatabase • New in ArcGIS 10 • Each MXD has one • Default location is <user home directory>/ArcGIS/Default.gdb • Can be changed under File>Map Document Properties… or the Getting Started dialog • Is the default output location for tools

  11. Rasters • GRID – ESRI proprietary format • Imagine (.img), GeoTiff (.tif), MrSid (.sid), many other raster formats are also supported in ArcGIS

  12. Other Formats • Stored in text files or database tables • X,Y coordinate data – usually from GPS • Street address data – a process called geocoding (requires suitable streets or parcel data) can convert addresses to points on your map

  13. Use ArcCatalog for: • Moving • Copying • Deleting • Renaming • Browsing • Metadata - creating, viewing, and editing Data Management Do NOT use Windows Explorer for spatial data management!!

  14. ArcCatalog Preview - used for data browsing Data Management

  15. Metadata • Metadata is data about data • For example, spatial extent, contact information, and projection • EPA Metadata Editor (EME): www.epa.gov/geospatial/eme.html

  16. Metadata ArcCatalog Metadata Used to learn about the data

  17. Data Sources • ESRI Data and Maps – DVDs distributed with every software upgrade, also online at the ESRI website • Federal clearinghouses • USGS National Atlas - www.nationalatlas.gov • USGS seamless server - seamless.usgs.gov • USDA/NRCS - datagateway.nrcs.usda.gov • EPA GeoData Gateway - https://geogateway.epa.gov/geoportal/catalog/main/home.page • EPA OTOP Geodata and tools (EPA only) – intranet.epa.gov/rtpgis/geodata.html • EPA Data Finder http://www.epa.gov/datafinder/ • EPA Regional offices

  18. Data Sources • State and local agencies • Most states have GIS data portals/clearinghouses • Many counties have GIS departments • Universities can also be a good source, for example, www.lib.unc.edu/reference/gis/onlinedata.html

  19. Map Services • Geography Network – Hosted by ESRI, built into ArcGIS • igeo.epa.gov – EPA intranet only • Geodata.epa.gov

  20. Some National GIS Datasets • Land-cover – 1992, 2001, 2006 and change, www.mrlc.gov • Elevation – NED, 30 meter resolution, ned.usgs.gov • Hydrology – NHDPlus, www.horizon-systems.com/nhdplus • Soils – STATSGO, datagateway.nrcs.usda.gov • SSURGO is finer resolution, but not available for the entire country • Roads – ESRI Streets data – on the ESRI data and maps DVDs, and TeleAtlas – OTOP website • Demographics – US Census Bureau, www.census.gov

  21. Regional/Local GIS Data • Placeholder to be customized for each location/Region

  22. Imagery • EarthExplorer – USGS site with free download of aerial photography, Landsat and other satellite imagery – edcsns17.cr.usgs.gov/EarthExplorer • GlobeXplorer ImageConnect – link from OTOP page

  23. Water quality GIS data • NHD plus – www.horizon-systems.com/nhdplus • EPA WATERS – www.epa.gov/waters/data • NADP – nadp.sws.uiuc.edu/data • USGS NWIS – water.usgs.gov • WBD – www.ncgc.nrcs.usda.gov/products/datasets/watershed

  24. Air quality GIS data • CASTNet – www.epa.gov/castnet • EPA Air data – www.epa.gov/air/data • AIRQUEST – intranet.epa.gov/oar/airquest (EPA only)

  25. Human health GIS data • Often collected by county, and not always in GIS friendly formats, or even digitally • CDC – www.cdc.gov • Census Bureau – www.census.gov

  26. Creating Your Own Data • There is an extensive set of editing tools in ArcGIS. We will cover them in chapter 8. • You can add point, line and polygon graphics to your maps using the drawing toolbar • You can also convert graphics to features for the ability to add attributes, useful in display and analysis

  27. NHD 1:100,000 NHD 1:24,000 Scale, Extent and Resolution Small scale, lower resolution (less detail) Large scale, high resolution (more detail)

  28. Troubleshooting • A red exclamation point next to a layer indicates the path to the data is broken. To correct the path, right click the layer and choose Data>Repair Data Source from the context menu. • A gray check in a layer’s checkbox means the layer is not visible because the map is not at an a appropriate scale. Zooming in or out (depends on the layer) will make it visible.

  29. Coordinate Systems/Projections • Required to display 3D data in 2D • Projection and datum should be included in metadata • Data acquired from different sources (or even the same source) may be in different projections and/or datums • Good database management practice is to keep all data in the same coordinate system, NOT geographic (lat/lon) • Use the Project tool to convert from one projection to another • If at all possible, avoid projecting rasters • More on projections (and datums) in chapter 5

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