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HDF4 OPeNDAP Project Progress Report

HDF4 OPeNDAP Project Progress Report. MuQun Yang and Hyo-Kyung Lee. OPeNDAP Review. A software framework that allows simple access to remote data D ata A ccess P rotocol Client-server model Widely used by Earth Science Community. OPeNDAP Reivew. Users. Hyrax. IDV.

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HDF4 OPeNDAP Project Progress Report

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  1. HDF4 OPeNDAP ProjectProgress Report MuQun Yang and Hyo-Kyung Lee HDF Developers' Meeting

  2. OPeNDAP Review • A software framework that allows • simple access to remote data • Data Access Protocol • Client-server model • Widely used by Earth Science • Community HDF Developers' Meeting

  3. OPeNDAP Reivew Users Hyrax IDV libnc-dap AIRS DAP Visualization Tools OPeNDAP Clients OPeNDAP Servers HDF4 Files

  4. OPeNDAP Concept Typical Remote Access View Data (User) Remote Data (HDF4) FTP/HTTP Visualization Tools (gradsdap) Visualization tools (e.g. grads) Handler (hdf4_handler) Client Library (libnc-dap) Server (apache) DAP Protocol (via http) HDF Developers' Meeting

  5. Goals Better Access for HDF-EOS2 via DAP • Faster download through selection • Quicker analysis through visualization HDF Developers' Meeting

  6. HDTV Problems You bought a HDTV but... • No HD signal • Needs more Channels in HD • Cable Service Provider Problem HDF Developers' Meeting

  7. HDF4 Problems You downloaded a viewer but... • No CF convention • Needs more HDF4 data in CF • Data Service Provider Problem HDF Developers' Meeting

  8. Challenges: HDF-EOS2 HD Signal Challenge • CF convention (e.g. NetCDF model) • Syntax • Clients expect a certain data structure • Semantics • Clients expect some key attributes HDF Developers' Meeting

  9. Challenges: HDF-EOS2 More Channels in HD Challenge • DVD/VHS/VCD/LD >>> Blue-Ray • Can all titles be delivered in HD? • HDF4/HDF-EOS2 >>> HDF5/HDF-EOS5 • Can all HDF-EOS2 be delivered in CF? HDF Developers' Meeting

  10. Solution: New HDF4 Handler HD Signal Solution • Syntax • Generate the correct DAP data type. • Add shared geo-location information. • Semantics • Insert additional key attributes. HDF Developers' Meeting

  11. Solution: New HDF4 Handler More Channels in HD Solution • Use Metadata parser • Pro: simple • Con: limited channels • Use HDF-EOS2 library • Pro: maximum channels • Con: install HE2 library first HDF Developers' Meeting

  12. Solution Comparison HDF Developers' Meeting

  13. Quick Implementation • Parse Metadata – hdf5_handler • Use HDF-EOS2 library – h4toh5 IDL ncBrowse Ferret MATLAB NCL IDV GrADS ODC HDF Developers' Meeting

  14. Current Status • MODIS / AIRS Grid and Swath • Other Projections (Polar, Sinusoidal) • Testing IDL ncBrowse Ferret MATLAB NCL IDV GrADS ODC HDF Developers' Meeting

  15. HDF-EOS2 in CF via DAP • Finally, Happy Data Consumer! AIRS Grid AIRS.2008.10.27.L3.RetStd001.v5.2.2.0.G08303124144.hdf http://daac.gsfc.nasa.gov/daac-bin/whom/mk_page_cgi.pl?PATH=datapool/AIRS/Level3_V005/01_AIRX3STD/2008/10 AIRS Swath ftp://airspar1u.ecs.nasa.gov/data/s4pa//Aqua_AIRS_Level2/AIRX2RET.005//2008/330/AIRS.2008.11.25.143.L2.RetStd.v5.2.2.0.G08331121849.hdf MODIS Grid MOD08_D3.A2008284.005.2008289105354.hdf http://modis-atmos.gsfc.nasa.gov/MOD08_D3/acquiring.html MODIS Swath MOD06_L2.A2001222.0025.004.2003127111841.hdf http://modis-atmos.gsfc.nasa.gov/MOD06_L2/acquiring.html HDF Developers' Meeting

  16. Limitations – Missing Attributes • MODIS Grid – Rain fall • AURA OMI Grid - Ozone No Unit! HDF Developers' Meeting

  17. Limitations – Missing Names • How to Match Dimension Names? HDF4 Handler pressureStd → Level NetCDF4 Handler HDF Developers' Meeting

  18. Limitations – Missing Values • How to Supply Missing Dimension Values? MISR_AM1_TC_CLASSIFIERS_P020_O000995_F06_0011.hdf HTTP/1.0 200 OK XDODS-Server: 3.7.9 XOPeNDAP-Server: 3.7.9 XDAP: 3.1 Content-Type: text/plain Content-Description: dods_error Cache-Control: no-cache Error { code = 1002; message = "An internal error was encountered: This HDF-EOS2 file has multiple Grids with different dimension sizes. Please report this to support@opendap.org "; }; HDF Developers' Meeting

  19. Solution – Customization • Provide an option for handler customization to generate fully CF-compliant output • Create a separate XML input file for handler and feed it into the handler. • Insert attributes, renaming rules, and missing values by putting them in the XML input. • This requires a knowledge about the characteristics of data in advance. HDF Developers' Meeting

  20. Solution – Customization • Example: Attributes, Renaming, Values <xml> <variable name=‘RrLandRain’> <attr name=‘unit’ type=‘String’> inches</attr> <attr name=‘_FillValue’ type=‘Int16’>-1</attr> </variable> <rename from=‘GeoXTrack’ to=‘lon’ ></rename> <rename from=‘pressStd’ to=‘lev’></rename> <insert name=‘NAltitudeDim’ size=10 type=‘Int8’> 0,1,2,3,4,5,6,7,8,9 </insert> </xml> HDF Developers' Meeting

  21. Summary • HDF4 Access via OPeNDAP • Is Easy, Efficient and Fast • Is Cool like HDTV • Adding CF is not straightforward • Use HDF-EOS2 library • Is Essential • Maximize the data coverage HDF Developers' Meeting

  22. Future Work (Short Term) • Expand test-suite with data pool • Release through OPeNDAP website • Support for Swath via Parsing • Support for Point data type via HDF-EOS2 library HDF Developers' Meeting

  23. Future Work (Long Term) • General HDF4 Files Support • Customization for CF option • HE2 to DAP Mapping Documentation HDF Developers' Meeting

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