Using a Friendly OPeNDAP Client Library to Access

HDF5 Data

MuQun Yang and Hyo-Kyung Lee

(The HDF Group)

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OPeNDAP Review

• A software framework that allows simple access to remote data• Data Access Protocol• Client-server model• Widely used by Earth Science Community

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Client Library(libnc-dap)

DAP Protocol (via http)

Server(apache)

Handler(hdf4_handler)

Remote Data(HDF4)

View Data (User)

OPeNDAP Concept

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Visualization Tools

(gradsdap)

Typical Remote Access

FTP/HTTP

Visualization tools

(e.g. grads)

DAP Protocol (via http)

Server(apache)

Remote HDF5View Data (User)

OPeNDAP HDF5 Handler

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HDF5 Handler

DAP Protocol (via http)

Server(apache)

View Data (User)

OPeNDAP HDF5 Handler with HDF-EOS5

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HDF5 Handler

Remote HDF5

Client Library(libnc-dap)

Visualization tools

(grads)

Remote HDF-EOS5

HDF5 Handler

DAP Protocol (via http)

Server(apache)

View Data (User)

OPeNDAP HDF5 Handler with HDF-EOS5

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HDF5 Handlerw/ CF options

Remote HDF5

Client Library(libnc-dap)

Visualization tools

(grads)

Remote HDF-EOS5

Day After Server Tweaks

• Finally, Happy Clients!

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HDF5-Friendly OPeNDAP Client Library

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DAP Protocol (via http)

Server(apache)

View Data (User)

HDF5 Handler

Client Library(libnc-dap)

Visualization tools

(grads)

Remote HDF5

HDF5 Handlerw/ CF options

HDF5-FriendlyClient Library(liboc-dap)

HDF5 GroupsView Groups???

Example: Groups in HDF5Traditional OPeNDAP client library: It’s an attribute that I don’t understand. I’ll ignore it.

HDF5-Friendly OPeNDAP client library: I was waiting for this key attribute to re-construct HDF5

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Example: Reference in HDF5

• Important for NPOESS

• Object / Regional Reference

• Map to DAP URL

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• One more reason:

Help Clients to view Swath

Our Client Library(prototype)

HDF5 Handler

DAP Protocol (via http)

Server(apache)

View Data (User)

Visualizing HDF-EOS5 Grids

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HDF5 Handlerw/ CF option

Remote HDF5

Client Library(libnc-dap)

Visualization tools

(grads)

Remote HDF-EOS5

Swath

Visualizing HDF-EOS5 Swath Problem

???

HDF5-FriendlyClient Library(liboc-dap)

Visualization Tools

(gradsoc)

View Swath

Demo: MLS swath via GrADS

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CO at these elevations is a measure of pollution

lower stratosphere

upper stratosphere

Before

After

CO level near Beijing, China before, during and after Olympics

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

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Credits

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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. 

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