1. NASA HDF-EOS File Format Overview Joseph M Glassy, Director, MODIS Software Development at NTSG School of Forestry, Numerical Terradynamics Simulation Group University of Montana, Missoula Montana USA

2. Introduction Goals: –Introduce basics of the HDF-EOS scientific file format –Provide examples using FPAR, LAI and PSN, NPP Level 4 product tiles.

3. HDF-EOS -- Background NASA’s original requirements: -needed a platform-portable, self-annotating file format… -Very flexible “container” (like “tar”) required -Availability of an efficient management API a must… -Needed to encapsulate geolocation information for (3) data models: Point, Grid, and Swath -Needed to support multiple objects, of all data types, in N dimensions…

4. Scientific File Formats Off the shelf choices were limited to: –CDF …common data format, older… –geoTIFF …good, but had little support… –netCDF...an improvement over common data format –HDF..NCSA’s hierarchical data format

5. A Solution: NASA’s Hybrid HDF-EOS …built on well-supported HDF v.4.0.x foundation …built to support ISINUS nested grid and others …custom VGROUP for “Grid”,”Point”,”Swath” …could handle up to 255 separate N dimensional objects of any numeric scalar data type …excellent support for metadata attributes at every level {file, grid, gridfield} built in… Platform (byte-ordering) portability via XDR internal functionality

6. HDF-EOS : The Down Side… …did the world really need a “new” data format? …virtually no COTS S/W support at first, and still slow to fully embrace… …early HDFEOS API’s were buggy, under- featured…

8. HDF-EOS : Key Ingredients Pre-Defined Attributes (via special API fx) –Scale (gain) –Offset –_Fillvalue –Units –Range {min, max} –Longname User Attributes (anything goes…)

9. Must apply {gain, offset} to decode from digital to biophysical values… –Analytical = gain * (Digital – offset) –Digital = (Analytical / gain) + offset Remember reverse BIT-ORDER for QA Fields with embedded bitfields: –7 6 5 4 3 2 1 0 –---------------------- –0 1 0 1 0 0 1 1 HDF-EOS : Key Ingredients

10. HDF-EOS Browsers COTs browsers are typically built on HDFEOS API library Browsers like HDF-Explorer offer a visual object hierarchy experience.. RSI/Kodak’s IDL also supports HDF (soon HDF- EOS) through a more traditional command line interface… LOA’s HDFLook -- very good for workstations JPL’s WebWinds is a good, Java-based tool Other key tools: ncdump (simple table of contents generator and primitive data dump capabilities)

11. Example: Noesys’ Visual Object Hierarchy

12. Embedded QA Bitfield Legend (via Noesys 2.0)

13. …with easy Visualization…

14. HDF-EOS: What’s Next… HDF-EOS v5 based on HDF v5 coming soon… HDF v5 stores files larger than 2 Gb… HDF v5 is a major change from the v4 family… Information: http://hdfeos.gsfc.nasa.gov/hdfeos/workshop.html