ESDS Program

Mapping HDF5 to DAP2


Data Access Protocol Version 2 (DAP2) and Hierarchical Data Format Version 5 (HDF5) are endorsed by NASA Headquarters as recommended by NASA's Earth Science data systems standards. A significant number of HDF5 objects directly match DAP2 objects. However, because HDF5 and DAP2 have different data models, it can be difficult to fully map all HDF5 objects to DAP2 objects, yet several difficult-to-map HDF5 objects are essential for Earth Science applications. This technical note presents general HDF5-to-DAP2 mapping information, covering HDF5, datasets, groups, and attributes. Considerable detail is presented for the representation of those crucial, difficult-to-map objects that are required for Earth Science applications. This document also includes information about special HDF5-to-DAP2 mapping that enables easy access to NASA HDF-EOS5 data via DAP2 clients.


The Mapping HDF5 to DAP2 was recommended for informational use in NASA's Earth Science Data Systems in September 2011.

Technical Note

Mapping HDF5 to DAP2

User Resources

OPeNDAP project home page

NASA Earth Science Community Recommendations for Use


HDF5 and DAP2 are both endorsed Earth science data systems standards. Both are in widespread use within NASA's Earth science community. This document provides an excellent introduction to and solution to the problem of how to map objects of the two specifications to each other.


No specific weaknesses were identified by the reviewers. However it was suggested that a valuable addition would be source code for a reference implementation of a program that implemented the mapping.


This document very specifically addresses the mapping between two existing specifications. As such it clearly applies to those who are working with both. However, as an informational document it may also be of interest to users of just one of the two specifications or those interested in Earth science data and/or metadata.


The document does not provide a comprehensive or complete mapping.

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