The HDF-EOS5 Tutorial
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The document describes HDF-EOS5, an extension of HDF used by NASA for Earth science data. HDF-EOS5 is based on HDF5 and contains standardized structures for gridded, swath, point, and zonal average data. It provides a library for reading, writing, and manipulating these data structures and their associated metadata. The library contains functions prefixed with "HE5_" for accessing, defining, input/output, inquiry, and subsetting HDF-EOS5 data.
The HDF-EOS5 Tutorial
- 1. The HDF-EOS5 Tutorial Ray Milburn L3 Communciations, EER Systems Inc. 1801 McCormick Drive, 170 Largo, MD 20774 USA Ray.Milburn@L-3com.com
- 2. What is HDF-EOS ? • HDF (Hierarchical Data Format) is a disk-based format chosen by NASA as a standard for EOS program • HDF-EOS is an extension to HDF which standardizes common Earth Sciences data structures • HDF-EOS2 based on HDF4 is used operationally by EOS TERRA and AQUA instrument teams • HDF-EOS5, based on HDF5 is newer and will be used by EOS AURA instruments • Contains Geolocation Information: – Structural metadata links Geolocation and science data 2
- 3. HDF-EOS 5 Library • Provides Grid/Point/Swath/ZA interfaces • Allows to create/access Grid/Point/Swath/ZA and manipulate their objects (data sets, attributes, etc.) • Written in C with FORTRAN-77 wrappers • C-function names prefixed with “HE5_” • FORTRAN-77 calls have similar naming convention 3
- 4. Grid Structure • Data organized by regular geographic spacing, specified by projection parameters. • Structure – Multidimensional data arrays – Geolocation information is given implicitly by projection parameters contained in structural metadata 4
- 6. Swath Structure • Data is organized by time or track parameter • Data spacing can be irregular • Structure – Geolocation information stored explicitly in Geolocation Field (2-D array) – Data stored in multidimensional arrays – Time stored in 1-D or 2-D array – SM links Geolocation and science data 6
- 8. Point Structure • Data is specified temporally and/or spatially, but with no particular organization • Structure – Tables used to store science data at a particular Lat/Long/Height – Up to eight levels of data allowed. Structural metadata specifies relationship between levels. 8
- 9. Point Data Example 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 -149.48 -122.41 -77.00 -90.15 -90.05 -122.26 -76.45 -79.23 -118.14 -96.48 -112.00 -71.07 -106.40 -77.56 -87.25 -122.20 -104.59 -78.00 -93.15 -87.37 -80.11 Temp(C) Dewpt(C) 15.00 5.00 17.00 5.00 24.00 7.00 27.00 11.00 22.00 7.00 25.00 10.00 27.00 4.00 30.00 14.00 25.00 4.00 32.00 8.00 30.00 10.00 28.00 7.00 30.00 9.00 28.00 9.00 30.00 8.00 32.00 15.00 31.00 16.00 28.00 7.00 32.00 13.00 28.00 9.00 19.00 3.00 9
- 10. Zonal Average (ZA) Structure • Generalized array structure with no geolocation linkage • Data can be organized by time or track parameter • Data spacing can be irregular • Structure – Data stored in multidimensional arrays – Time stored in 1-D or 2-D array – SM links science data 10
- 11. HDF-EOS Grid Structure • Usage - Data which is organized by regular geographic spacing, specified by projection parameters. • Structure – Any number of 2-D to 8-D data arrays per structure, one per data type (e.g. temperature) – Geolocation information contained in projection formula, coupled by structural metadata. – Any number of Grid structures per file allowed. 11
- 12. HDF-EOS Swath Structure • Usage - Data which is organized by time, monotonic geolocation, track parameter. Spacing can be irregular. • Structure – Geolocation information stored explicitly in Geolocation Field (2-D array) – Data stored in 2-D or 3-D arrays – Time stored in 1-D or 2-D array, TAI is standard. – Geolocation/science data connected by structural 12 metadata
- 13. HDF-EOS Point Structure • Usage - Data which is specified temporally and/or spatially, but with no particular organization. • Structure – Tables (Vdatas) used to store science data at a particular Lat/Long/Height. – Up to eight levels of data allowed. Structural metadata specifies relationship between levels. 13
- 14. HDF-EOS ZA Structure • Usage - Data which is organized by time, track parameter. Spacing can be irregular. • Structure – Data stored in 2-D or 3-D arrays – Time stored in 1-D or 2-D array, TAI is standard. – Science data connected by structural metadata 14
- 15. Basic HDF-EOS5 Functions • Access - Open, create, close objects/files • Definition - Set key parameters of data sets • Input/Output - Read/Write data • Inquiry - Return information about data • Subset - Read data from specified region 15
- 20. Definition GRID: • HE5_GDdefdim/he5_gddefdim • HE5_GDdefproj/he5_gddefproj • HE5_GDdeforigin/he5_gddeforigin • HE5_GDdefpixreg/he5_gd_defpreg 20
- 24. Input/Output GRID: • HE5_GDwritefield/he5_gdwrfld • HE5_GDreadfield/he5_gdrdfld • HE5_GDwriteattr/he5_gdwrattr • HE5_GDreadattr/he5_gdrdattr 24
- 25. Input/Output POINT: • HE5_PTwritelevel/he5_ptwritelevel • HE5_PTreadlevel/he5_ptreadlevel • HE5_PTwriteattr/he5_ptwrattr • HE5_PTreadattr/he5_ptrdattr 25
- 26. Input/Output SWATH: • HE5_SWwritefield/he5_swwrfld • HE5_SWreadfield/he5_swrdfld • HE5_SWwriteattr/he5_swwrattr • HE5_SWreadattr/he5_swrdattr 26
- 27. Input/Output ZA: • HE5_ZAwrite/he5_zawrite • HE5_ZAread/he5_zaread • HE5_ZAwriteattr/he5_zawrattr • HE5_ZAreadattr/he5_zardattr 27
- 29. Inquiry POINT: • HE5_PTlevelinfo/he5_ptlevelinfo • HE5_PTinqattrs/he5_ptinqattrs • HE5_PTattrinfo/he5_ptattrinfo 29
- 30. Inquiry SWATH: • HE5_SWinqdatafields/he5_swinwdflds • HE5_SWinqgeofields/he5_swinqgflds • HE5_SWinqattrs/he5_swinqattrs • HE5_SWattrinfo/he5_swattrinfo 30
- 31. Inquiry ZA: • HE5_ZAinquire/he5_zainquire • HE5_ZAinfo/he5_zainfo • HE5_ZAinqattrs/he5_zainqattrs • HE5_ZAattrinfo/he5_zaattrinfo 31
- 32. Programming Model • Open the HDF-EOS5 file • Create or Attach to a specified Grid/Swath/Point/ZA object • Define key object features and/or perform necessary operations (with the data sets, attributes, etc) • Detach from the Grid/Swath/Point/ZA object • Close the HDF-EOS5 file 32
- 33. HDF-EOS Tools and Utilities • heconvert - command-line utility to convert HDF-EOS2 objects to HDF-EOS5 objects • HE5View - X-Motif based tool which displays all parts of the HDF-EOS5 objects • JEB - Java EOS Browser - Java based tool to display HDF4, HDF-EOS2 and HDFEOS5 objects 33