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Lecture 04: Data Storage and Representation & Access to Spatial Data

Lecture 04: Data Storage and Representation & Access to Spatial Data. Geography 128 Analytical and Computer Cartography Spring 2007 Department of Geography University of California, Santa Barbara. Traditionally, the paper map has performed a storage function for spatial information

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Lecture 04: Data Storage and Representation & Access to Spatial Data

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  1. Lecture 04: Data Storage and Representation &Access to Spatial Data Geography 128 Analytical and Computer Cartography Spring 2007 Department of Geography University of California, Santa Barbara

  2. Traditionally, the paper map has performed a storage function for spatial information Computer cartography requires information to be digital and stored explicitly Storage is increasingly distributed over networks Many mapping programs require local storage of data Cost and size restraints now less important Storage Media

  3. Evolution of Storage Media

  4. Bit - the most basic information unit in a binary system (1 / 0) 1 Byte = 8 bits Binary (2-based), Decimal(10-based), and Hexadecimal (16-based) System Binary Operator – AND, OR, NOT Data on a disk -Sectors, Tracks, Platters File system – File, Directory Physical Storage

  5. Map data is stored in the computer’s memory in a physical data structure (i.e. files and directories). Files can be written in binary or as ASCII (American Standard Code for Information Interchange) text. Binary is faster to read and smaller, ASCII can be read by humans and edited but uses more space. Maps as Numbers

  6. ASCII Table

  7. ASCII Table (extend)

  8. Cartographic data sets are typically large Need to reconfigure data formats, structures etc. Storage Efficiency and Data Compression • Seek to retain information content, lose volume. • Is redundancy necessary?

  9. Rasters vs. Vectors

  10. Physical Compression 4,513,410 m N;587,310 m E; Zone 18,N (32 characters, 15 digits) 4513410 587310 (13 digits, one space) Need metadata 98 96 7F 0F 42 3F (six bytes) Logical Compression Drop last two digits (10 ASCII or 2 bytes per coordinate) Storing Coordinates (Vector)

  11. Run-length encoding Quad-trees … Raster data Compression

  12. DLG – Digital Line Graphs (1:24,000; 1:100,000; 1:2,000,000) DEM – Digital Elevation Model (1:24,000; 1:250,000) GIRAS – Land-use and Land-cover Digital Data (1:100,000; 1:250,000) GNIS – Digital Cartographic Text Data Storage Formats for Cartography- U.S. Geological Survey

  13. Data Storage Formats for Cartography- U.S. Geological Survey USGS DLG format

  14. Data Storage Formats for Cartography- U.S. Geological Survey USGS 1:250,000 3-arc second DEM format (1-degree block)

  15. Data Storage Formats for Cartography- U.S. Geological Survey USGS 1:24,000 30 meter DEM format (7.5-minute quadrangle)

  16. WDB I (1:12M base, 100K points) WDBII (1:3M base, 6M Points) DCW 1:1M base- 4 CDs, 14 layers DMAs VPF Data Storage Formats for Cartography- CIA World Data Bank

  17. Vector formats are either page definition languages or preserve ground coordinates. Page languages are HPGL, PostScript, and AutoCAD DXF. Proprietary GIS Formats Arc/Info, ArcGIS MapInfo … Data Storage Formats for Cartography- Industry “Standard” Vector Formats

  18. Most raster formats are digital image formats. Most GISs accept TIF, GIF, JPEG or encapsulated PostScript, which are not geo-referenced. GeoTIFF is true geographic data format Data Storage Formats for Cartography- Industry “Standard” Raster Formats

  19. Map libraries Reference books State and local agencies Federal agencies Commercial data suppliers e.g. GeographyNetwork.com, Rand McNally, Thompson, NAVTEQ, maps.com Finding Existing Map Data

  20. Existing map data can be found through a map library, via network searches, or on media such as CD-ROM and disk. Many major data providers make their data available via the World Wide Web, a network of file servers available over the Internet. GIS vendors package data with products. Existing Map Data

  21. Commercial vendors

  22. U.S. Geological Survey (USGS) National Oceanic & Atmospheric Administration (NOAA) Census Bureau National Geospatial-Intelligence Agency (NGA) Environmental Protection Agency (EPA) many more... Federal Data Agencies

  23. National Spatial Data Infrastructure http://www.fgdc.gov/nsdi/nsdi.html

  24. Geodata.gov

  25. National Spatial Data Clearinghouse

  26. USGS: National Mapping

  27. National Map Viewer

  28. DOQQ (Digital Orthophoto Quarter Quadrangle ) plus DLG streets

  29. DRG (Digital Raster Graphics) plus DLG streets

  30. Seamless data download

  31. Geospatial Onestop Geography Network EROS Data Center FGDC: Standards Alexandria Digital Library State data centers e.g. Teale in CA MapQuest NAVTEQ, etc. Counties, municipalities, universities, tribes, etc. Other components of the NSDI (Portals, standards, services, data)

  32. U.S. Bureau of the Census

  33. National Oceanic and Atmospheric Administration (NOAA) Weather and other data

  34. Eros Data Center • Distributed active archive center • Sioux Falls, SD • Operated by USGS

  35. US GeoDataftp access toDEMDLGGNISGIRASetc.

  36. GNISFeature locations

  37. GIRASLand Use and Land Cover Data

  38. GIRAS into Arc/Info (GIRASARC)

  39. Terrain dataDEMDLG ContoursDCW Contours

  40. Spatial Data Structure Next Lecture

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