NASA’s Earth Observation System (EOS) is a monumental accomplishment of engineering and creative prowess, launching many satellites, data analysis programs, and careers. Imagery that is collected by satellites is beamed down to earth to be processed into a variety of formats. One of the most common data types for disseminating these images is as an HDF-EOS file type. HDF-EOS files are prescribed as the standard data format for information collected by the Aqua, Terra, and Aura satellites. For my Thesis I am using the National Snow and Ice Data Center‘s MOD10A2 snow cover product, which is delivered as an HDF file. These files are fairly difficult to manage, and are not readable using most standard GIS software (ArcMap, R, etc). There are a number of ways to manage these files, and for my purposes I will be converting them to the more universal Geo-TIFF format. This page describes my process for managing these data. This page is developed as my deliverable product for my Directed Independent Study titled HDF-EOS management processing completed in partial fulfillment of my academic plan of study as an M.S. Geography candidate at Western Washington University. These pages are designed to be a resource for anyone seeking to use HDF-EOS data for their own research.
Select your Data of Interest
NASA’s Earth Observing System Data and Information System (EOSDIS) is the clearinghouse for EOS data. There is a handy graphical user interface that you can use to explore the EOS data available called Reverb. Through Reverb you can move around the world and explore the different data available, and focus in on a specific geographic or temporal range of interest. Here is a link to my area of interest.
All data products are delivered as raster tiles called granules. Each granule represents an individual raster ’tile’ defined by the naming convention. Reverb has a hard limit of 2000 granules to add to your cart at any one time. You may need to process your request in more than one batch, either by region, or more likely, by time period.
First ask yourself, how many HDF-EOS files do I need to work with? NASA’s Echo data management portal allows you to re-project HDF files and save them as GeoTIFFs easily, limited to 1,000 granules or less. If you have a small area of interest (and short time span), your best bet is to select the files that you need and try to have them processed by NASA on their home servers using the Perform Service options. Save yourself some heartache! Here is a link to an excellent tutorial produced by NASA. If you have a large area of interest that covers two or more granules you may want to follow the steps below which can reproject and mosaic your data all at once. I suppose you could mosaic your data at the end on your own machine but that is computationally intensive. If you determine that you do need to perform these transformations on your own, proceed with caution.
HEG Conversion Tool (http://hdfeos.org/software/tool.php#HEG)
MODIS Reprojection Tools
This page is still under construction.