I am now working with GEFED dataset, which is a global wild file dataset.You can download one from FTP: fuoco.geog.umd.edu; Login name: fire; Password: burnt; The file is stored into gfed4/monthly/. Any one file will be example.
My task is to translate the hdf file into tif, which can be done by gdalUtils package. But there is no georeferecing information in the file. Instead, the only information I could find is from the data manual (can be found in gfed4 folder in that FTP): "Each product file contains seven data layers, each stored as a separate HDF4 Scientific Data Set (SDS). Units apply to each layer after multiplying by the specified scale factor. Each data layer has 720 rows and 1440 columns which correspond to the global 0.25◦ GFED grid. The center of the upper left grid cell is located at longitude 179.875◦W, 89.875◦N.". I think the original src can be written from this statement. And I can pass it to a_src and a_ullr variable in gdal_translate command. But I have no idea what is the string for a_src.