How to convert the ASTER imagery (HDF format) into a more widely readable format.
[note: in 2007 some imagery from ASTER is arriving as 15 GeoTIFF files. If your ASTER data is in TIF files see this posting instead]
The program Geomatica Freeview is a good program for browsing and viewing HDF files, but it does not allow you to export to another format.
The HEG Tool (Java) allows you to convert HDF-EOS formated files to GeoTIFF files that can be imported by a variety of GIS programs.
A. Preliminary steps
- Download and install the HEG Tool as well as the most recent Java runtime (v1.2 or greater). In Windows it is best if you install both programs into directories without spaces anywhere in the path. I used
C:\HEG\ and C:\JAVA\
- Locate appropriate imagery from ASTER, MODIS, or other sources in HDF format. The USGS GLOVIS Viewer is particularly useful for this step.
- Order scenes from NASA using the DAAC Data portal (account required).
- When the data arrives download it.
B. Using HEG Tool
Converting HDF-EOS to GeoTiff in HEGTOOL 2.7
- File Menu > Open
- Select from Fields: ImageData1
- Click Down Arrow below
- From Output Field Type choose Multiband GeoTiff
- Under Projection: choose UTM if you want it to be in the same reference system as the DEM
- Click Browse… and name the output TIFF file.
In naming the output follow naming conventions for your project. You might choose AST and the last part of the file numbers as a filename for the .tif
- Click Accept below
- Back in Fields click ImageData2 and Down arrow
- Click Accept below
- Fields: click ImageData3N and Down arrow
- Click Accept
- Click Run
Further instructions are available in an instructional PDF served by the USGS
The resulting GeoTIFF can be opened in Arcmap. You might want to rearrange the display order of the bands as RGB. This can be done under symbology.
If you have additional separate bands you'd like to combine into a GeoTIFF or IMG file (which allows for more bands), use the ArcToolbox function:
Data Management > Raster > Composite Image...
to combine these many bands into a single multiband image.
C. What are the bands in an ASTER scene?
In Freeview and in the HEG Tool (under Objects) you will note that a variety of bands are available from a single ASTER HDF-EOS Swath file. Each band has a different spectral range.
- ImageData1, 2, 3N are Visible & Near infrared (VNIR) imagery at 15m resolution acquired at nadir (straight overhead).
- ImageData3B is the back-looking image acquired subsequently and used as a stereo-pair for DEM production
- ImageData4-9 are Short-Wave Infrared (SWIR) bands at 30m resolution, a longer wavelength, set at nadir.
- ImageData10-14 are Thermal Infrared (TIR) bands at 90m resolution, longer wavelength yet, set at nadir.
You may read more about the applications of these bands at the JPL ASTER website and the USGS ASTER website.
I used Bands 2 and 3n for this seasonality and vegetative production study in the Colca Valley.
For instructions about processing ASTER DEM files for use in Arcmap see this article.