HotdoG Proposal


The HotdoG project is an effort and suite of tools to convert HDF/HDF-EOS format into GeoTIFF format. This is the first of a potential series of incoming projects originating from The HDF Group -- the non-profit organization is interested in evaluating the ASF as a potential home for many of its projects. The HDF Group is an independently funded organization that started many years ago with major investment from NASA as the Hierarchical Data Format (HDF), version 4 and now version 5, is the de facto remote sensing data format for NASA missions, and an increasing number of other disciplines including bio medicine, radio astronomy, climate science, and other domains.

HDF is both a data and metadata format, as well as a model for representing and access information. There are numerous downstream tools that can read and write HDF data, including a growing number of Geospatial data tools (ESRI-based, and also OpenGeo and other community led efforts). In addition, major interoperability efforts are also occurring between the remote sensing community and the climate modeling community (which has traditionally favored NetCDF as opposed to HDF) because of the efforts in HDF5 to leverage a common data format and model.

HotdoG is poised to be a first of its kind in the form of bringing one of the major 2 data formats for science to the ASF (the other being the NetCDF format).


HotdoG is a software converter that converts Earth Science data in HDF/HDF-EOS format into GeoTIFF format. Doing so easily enables users of remote sensing data to interoperate with common GIS tools (like WebGIS, Web Processing, image analysis, and geo computational tools). We feel that the project is an incremental step, and an appropriate focus with tangible success possibilities by restraining our focus to HDF/HDF-EOS to GeoTIFF conversion.

There are numerous interesting paths that we can take the toolkit in -- as conversion from remotely sensed data to GeoTIFF involves ensuring that the HDF-EOS metadata elements can be appropriately represented using GeoTIFF headers, and the associated format. Furthermore, capturing the HDF's appropriate geo datum in GeoTIFF will be another important challenge.


GeoTIFF is a data and metadata standard for Earth science applications. It is based on binary Tagged Image File Format (TIFF). A GeoTIFF file has geographic (or cartographic) data embedded as tags within the TIFF file that are used to geo-locate the image. This is required for correct integration of the image in Geographic Information Systems (GIS) and other popular tools like Google Earth Pro.

In the recent years, GeoTIFF has gained popularity as a visualization format among NASA HDF Earth science user communities according to the NASA data user's survey. However, the conversion from HDF to GeoTIFF is not straightforward for end users because NASA HDF data products are diverse and organized in many different ways. For example, go to and you'll see many scripting language examples because no single script can correctly visualize all NASA HDF data.


The HEG tool is limited to some NASA HDF-EOS2 products (no support for HDF-EOS5 products) and it is not an open-source tool. The latest GDAL (version 1.9.2 and above) is an open-source tool but it cannot handle many non-HDF-EOS NASA HDF products such as TRMM (pure HDF4) and Aquarius (pure HDF5) correctly and automatically.

Initial Goals

We'll improve GDAL to support NASA HDF products better by handling geo-location information and physical meaning of data correctly and automatically.

We'll handle NASA products intelligently so novice users don't have to supply many options or figure out the details about the data products. For advanced users, we'll give a full control of accessing HDF products in many different ways so that the converted GeoTIFF file is scientifically valid and meaningful.

We aim to provide command line tools first and evolve them into a GUI tool.

Current Status

We're looking for people interested in HotdoG and to move the project into the Apache Community.


We will discuss the milestone and the future plan in an open forum. We plan to encourage an environment that supports a meritocracy. The contributors will have different privileges according to their contributions.


GIS and Earth Science

Core developers


HotdoG employs H4CF Conversion Toolkit for reading data and GDAL for writing GeoTIFF. In addition, we plan to integrate HotdoG with other products from new missions such as SMAP and IceSAT-2.

If HEG becomes available as open source, HotdoG will employ it as well for HDF-EOS2 products.

Known Risks

HDF-EOS2 and HDF-EOS5 libraries are distributed under the NOSA license that may not be compatible with Apache License. This will be vetted with the Legal Affairs Committee and if found incompatible we will find a different way to read HDF-EOS products.

HDF is a flexible format which affords for unusual objects such as Point & Zonal Averages (HDF-EOS), VData (HDF4), and compound datatype (HDF5) that present challenges in mapping to GeoTIFF. To mitigate this challenge the initial goals will focus on those objects which are more common place and easily map to GeoTIFF.


User's guide documentation will be provided via Doxygen. The guide will contain specific GeoTIFF conversion examples for each NASA HDF data product.

External Dependencies

Required Resources

Mailing List

Issue Tracking

JIRA HotdoG (HotdoG)

Other Resources

Initial Committers



Nominated Mentors

Sponsoring Entity

HotdoGProposal (last edited 2013-06-09 03:39:00 by PaulRamirez)