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Easy access HDF files via Hyrax. Kent Yang The HDF Group. Outline. Why OPeNDAP ? Hyrax features Hyrax modules Demos Suggestions. Why OPeNDAP?. Check metadata remotely (in various forms) Obtain the subset of data easily and efficiently Hide the original data sources

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easy access hdf files via hyrax

Easy access HDF files via Hyrax

Kent Yang

The HDF Group

outline
Outline
  • Why OPeNDAP?
  • Hyrax features
  • Hyrax modules
  • Demos
  • Suggestions
slide3

Why OPeNDAP?

  • Check metadata remotely (in various forms)
  • Obtain the subset of data easily and efficiently
  • Hide the original data sources
    • netCDF, HDF4, HDF5 or GeoTiFF, GRIB
  • Many popular earth science tools can visualize and analyze the data via OPeNDAP
  • OPeNDAP output(including subsets) can be downloaded as other formats
slide5

HDF(5) Hyrax modules

  • The visualization of HDF(5) data via Hyrax
    • What NASA users request the most
helpful hyrax feature bes keys
Helpful Hyrax feature – BES keys
  • BES keys to dynamic change the program flow
    • Easy for users to choose what they want
    • Easy for developers to add/revise features requested by users
example on using bes keys
Example on using BES keys

Float

CERES_Unfiltered_Radiances_all_toa_sw_rad[gmt_hour_index= 24][latitude =180][longitude= 360]

Float /CERES_Unfiltered_Radiances/all_toa_sw_rad[24][180][360]

hyrax modulation
Hyrax modulation
  • Core framework implemented in C++
  • Just need to provide DDS, DAS and Data to Hyrax libdap and BES
  • A handler can be sophisticated
  • HDF handler examples
    • Retrieve latitude and longitude for HDF-EOS grid
    • Interpolate the latitude and longitude for HDF-EOS swath with dimension map
    • Make sure the dimensions, variable names and attributes follow CF conventions
slide9

Non-CF

CF

Float /CERES_Unfiltered_Radiances/all_toa_sw_rad[24][180][360]

Float /CERES_Unfiltered_Radiances/all_toa_sw_rad[24][180][360]

Float CERES_Unfiltered_Radiances_all_toa_sw_rad[gmt_hour_index = 24][latitude =180][longitude= 360]

demo 2 hdf eos2 modis swath
Demo 2 – HDF-EOS2 (MODIS swath)

Swath with Dimension Map

hyrax modules that help the easy access
Hyrax modules that help the easy access
  • Filenet CDF module
    • Can download DAP output as a netCDF-3 or netCDF-4 classic files
  • NcML module
    • Add/delete/revise metadata information of the data source
    • Aggregate granules
slide14
Demo
  • GPM level 1B(HDF5)
hdf 5 and file netcdf demo
HDF(5) and file netCDF demo
  • FilenetCDF module can work with the HDF handlers to download the HDF files or subset of the files as netCDF-3 or netCDF-4 classic files that follow the CF conventions
hdf 5 and ncml demo
HDF(5) and NcML demo
  • NcML module can be used with HDF handlers to provide the missing CF information
  • AVHRR example
hdf 5 file netcdf and ncml demo
HDF(5), file netCDF and NcML demo
  • HDF handlers, NcML module and file netCDF module can work together
  • AVHRR example
summary of modules to serve hdf files
Summary of modules to serve HDF files

HDF(5)

files

DAP clients

(IDV, Ferret,

Panoply, IDL…...)

Hyrax core

Main engine

HDF(5) handlers

Alternative output

File netCDF

Supplement Info

NcML

netCDF

files

demo beyond the web service
Demo - Beyond the web service
  • BES standalone program
    • Connect the HDF handlers, the file netCDF module and the NcML module
    • End users can build Hyrax and use this program as a command-line tool
  • Can it be a standalone tool?

besstandalone -c /etc/bes/bes.conf -i in4-GPM-l1b > GPM-l1b.nc4

future performance
Future - Performance
  • Improve the BES caching mechanism
    • Critical for large file access and aggregation service
earth science group

Earth Science Group

Ted Habermann

Aleksandar Jelenak

H. Joe Lee

Joel Plutchak

John Readey

Kent Yang