Using a Friendly OPeNDAP Client Library to Access HDF5 Data

1
Using a Friendly OPeNDAP Client Library to Access
HDF5 Data

• MuQun Yang and Hyo-Kyung Lee
• (The HDF Group)

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

3
OPeNDAP Concept
Typical Remote Access
Remote Data (HDF4)
View Data (User)
FTP/HTTP
Handler (hdf4_handler)
Visualization Tools (gradsdap)
Visualization tools (e.g. grads)
Client Library (libnc-dap)
Server (apache)
DAP Protocol (via http)
4
OPeNDAP HDF5 Handler
Remote HDF5
View Data (User)
HDF5 Handler
Server (apache)
DAP Protocol (via http)
5
OPeNDAP HDF5 Handler with HDF-EOS5
View Data (User)
Remote HDF5
Remote HDF-EOS5
HDF5 Handler
Visualization tools (grads)
Server (apache)
Client Library (libnc-dap)
DAP Protocol (via http)
6
OPeNDAP HDF5 Handler with HDF-EOS5
View Data (User)
Remote HDF5
Remote HDF-EOS5
HDF5 Handler
HDF5 Handler w/ CF options
Visualization tools (grads)
Server (apache)
Client Library (libnc-dap)
DAP Protocol (via http)
7
Day After Server Tweaks

• Finally, Happy Clients!

IDL
ncBrowse
Ferret
MATLAB
NCL
IDV
GrADS
ODC
8

• HDF5-Friendly OPeNDAP Client Library

HDF5 Groups
View Groups
???
View Data (User)
Remote HDF5
HDF5 Handler
Visualization tools (grads)
HDF5 Handler w/ CF options
Server (apache)
Client Library (libnc-dap)
HDF5-Friendly Client Library (liboc-dap)
DAP Protocol (via http)
9
Traditional OPeNDAP client library Its an
attribute that I dont understand. Ill ignore it.
Example Groups in HDF5
HDF5-Friendly OPeNDAP client library I was
waiting for this key attribute to re-construct
HDF5
10
Example Reference in HDF5

• Important for NPOESS
• Object / Regional Reference
• Map to DAP URL

11
Our Client Library(prototype)

• One more reason
• Help Clients to view Swath

No Latitude and Longitude
Courtesy of NASA
12
Visualizing HDF-EOS5 Grids
Visualizing HDF-EOS5 Swath Problem
Swath
???
View Swath
View Data (User)
Remote HDF5
Remote HDF-EOS5
HDF5 Handler
HDF5 Handler w/ CF option
Visualization tools (grads)
Visualization Tools (gradsoc)
Server (apache)
Client Library (libnc-dap)
HDF5-Friendly Client Library (liboc-dap)
DAP Protocol (via http)
13
Demo MLS swath via GrADS
CO level near Beijing, China before, during and
after Olympics
lower stratosphere
CO at these elevations is a measure of
pollution
Before
During
After
upper stratosphere
14
Summary

• HDF5 Access via OPeNDAP
• Is easy
• Is used by NASA GES DISC to serve Aura files
• HDF5-Friendly OPeNDAP Client Library
• Is a prototype
• Serves HDF5 better(EOS swath)
• Benefits visualization clients

15
Credits
Mike Folk (The HDF Group) Robert McGrath
(NCSA) Peter Leonard, Daniel Kahn, Marghi Hopkins
(ADNET) Christopher Lynnes, James Johnson, Denis
Nadeau, Fan Fang (NASA) Jennifer Adams
(GrADS) Dave Brown (UCAR)
16
Acknowledgement

• This work was supported basing upon the
  Cooperative Agreement with the National
  Aeronautics and Space Administration (NASA) under
  NASA grant NNX06AC83A, NNX08A077A and
  NNX06AG75A. Any opinions, findings, and
  conclusions or recommendations expressed in this
  material are those of the author(s) and do not
  necessarily reflect the views of NASA.