An Overview of HDF-EOS (Part 1)

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HDF AND HDF-EOS WORKSHOP II (1998)

Source: http://hdfeos.org/workshops/ws02/presentations/ilg1/ilg1.ppt

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An Overview of HDF-EOS (Part 1)

  1. 1. An Overview of HDF-EOS (Part I) Doug Ilg Raytheon STX Doug.Ilg@gsfc.nasa.gov (301) 441-4089 1
  2. 2. Outline What is HDF-EOS? The Grid Interface The Point Interface 2
  3. 3. What is HDF-EOS? An HDF “Profile” An extension to HDF A library built “on top” of HDF Three new data objects Three new programming interfaces 3
  4. 4. Why HDF-EOS? Standard HDF lacks well defined ways of handling some key needs of EOSDIS Data structures for Earth remote sensing data and in-situ measurements with: – tightly coupled geolocation information – subsetting services based on geolocation ECS metadata model 4
  5. 5. HDF-EOS Platforms HDF-EOS Version 2.3 is available for: Sun SPARC - Solaris SGI - IRIX DEC Alpha - Digital UNIX HP 9000 - HP-UX IBM RS/6000 - AIX PC - Windows 95/NT 5
  6. 6. HDF-EOS Interfaces C and FORTRAN Interfaces for: Grid Data (GD) Point Data (PT) Swath Data (SW) 6
  7. 7. HDF-EOS Programming Model Writing – – – – – – – – open file create object define structure detach object* attach object* write data detach object close file Reading – – – – – – open file attach object inquire object read data detach object close file 7
  8. 8. A Grid Data Set 8
  9. 9. A Grid Structure Xdim Size: 2000 Projinfo Ydim Size: 800 9
  10. 10. Projections Supported Geographic Transverse Mercator Universal Transverse Mercator Hotine Oblique Mercator Space Oblique Mercator Polar Stereographic Lambert Azimuthal Equal Area Lambert Conformal Conic Polyconic Interrupted Goode’s Homolosine Integerized Sinusoidal 10
  11. 11. Components of the Grid Interface Access Definition Basic I/O Inquiry Subset Tiling 11
  12. 12. Tips on Writing a Grid Order of calls is significant: – Setting a compression method affects all subsequently defined fields – Setting a tiling scheme affects all subsequently defined fields 12
  13. 13. Grid Subsetting Features By Geolocation – GDdefboxregion/Gdextractboxregion By “Vertical” Field – GDdefvrtregion/GDextractvrtregion By Time (special case of vertical) Tip: use Geolocation, then Vertical/ Temporal 13
  14. 14. Compression Methods for Grids Run-Length Encoding Adaptive Huffman Gzip 14
  15. 15. A Point Data Set Lat 61.12 45.31 38.50 38.39 30.00 37.45 18.00 43.40 34.03 32.45 33.30 42.15 35.05 34.12 46.32 47.36 39.44 21.25 44.58 41.49 25.45 Lon Temp(C) Dewpt(C) -149.48 15.00 5.00 -122.41 17.00 5.00 -77.00 24.00 7.00 -90.15 27.00 11.00 -90.05 22.00 7.00 -122.26 25.00 10.00 -76.45 27.00 4.00 -79.23 30.00 14.00 -118.14 25.00 4.00 -96.48 32.00 8.00 -112.00 30.00 10.00 -71.07 28.00 7.00 -106.40 30.00 9.00 -77.56 28.00 9.00 -87.25 30.00 8.00 -122.20 32.00 15.00 -104.59 31.00 16.00 -78.00 28.00 7.00 -93.15 32.00 13.00 -87.37 28.00 9.00 -80.11 19.00 3.00 15
  16. 16. A Point Structure Lat Long Buoy ID 25.2645 091.2564 0126 22.3549 -93.4657 3564 23.2564 -89.2546 1256 Buoy ID 0126 0126 3564 1256 1256 0126 3564 Time Wave Height(ft) Temp(C) 01:26 2.54 18.4 05:56 3.58 18.2 06:28 12.64 16.4 08:12 7.58 17.1 09:58 7.76 17.2 09:59 4.23 20.1 10:16 10.23 17.5 16
  17. 17. The Point Interface Access Definition Basic I/O Inquiry Subset 17
  18. 18. Tips on Writing a Point Every level in a Point data set must be linked into the hierarchy. Before two levels can be linked, a link field must exist. 18
  19. 19. Point Subsetting Features By Time – PTdeftimeperiod/PTextractperiod By Geolocation – PTdefboxregion/PTextractregion Tip: use one or the other, not both 19
  20. 20. Compression Methods for Points NONE 20
  21. 21. Tips for HDF-EOS Coding Most operations (read, write, subset) work on a single field at a time. Region IDs and Period IDs are interchangeable and can be reused to further reduce a subset. Partial writes (appending) on compressed fields are only supported through tiling. 21

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