Thanks again Norman for your assistance I think I FINALLY got it and it was truly painful. After much to much time experimenting,
downloading HDF viewers, and other ancillary programs it turned out to be an apples and oranges type of thing. BTW, I only use ERMapper because it can read HDF files, my real goal is to get the data into ArcGIS, it would be nice to find a HDF4->GeoTiff converter but I guess a lot of people have asked for that .... I have found a HDF4->JPG
First off, I can't use SeaDAS as I have a PC and don't really have any interest in LINUX as an OS. I have been able to view the HDF using an HDF Viewer (NCSA HDFView 2.3 but that doesn't convert the HDF files)...
So, going from HDF to GIS seems to be a problem that a lot of people have had. GeoTIFF is an easy file format for ArcGIS to import so that is why I have been trying to use it. I searched on the forum's list (and the WWW) and found a couple of suggestions however, this post is only relevant for HDF-EOS so that won't work (http://oceancolor.gsfc.nasa.gov/forum/oceancolor/topic_show.pl?pid=534;hlm=adv;hl=geotiff#pid534
) and all the rest suggest using SeaDAS (see above).
The key to getting GeoTiff data into ArcGIS is moving from image space (2160 columns by 4320 rows of square pixels) to real-world coordinate space defined with a map projection. The GeoTiff world file (tfw) is used for georeferencing purposes and has the following format:
Line Number Values
Line1 Dimension of pixels in X direction
Line2 Rotation in X direction
Line3 Rotation in Y direction
Line4 Dimension of pixels in Y direction
Line5 Insertion point in X direction
Line6 Insertion point in Y direction
ERMapper seems to read the HDF fine, but not any of the associated metadata and/or projection info so an HDF comes in as a 2160 x 4320 raw image, not as a Plate Carre projected file. I then set the ERMapper import parameters so the HDF is projected in Geographic (Lat/Long) with Decimal Degrees as the units with the pixel size to .083 x .083 and the origin as -180.0, 90. Then I output the file as a GeoTiff (with a tfw, the header info is below) and now I am finally done !
tfw (Tiff World File)
Boy it was a long process and I have read on the internet that people have a little bit of a problem with HDF-EOS but I could find no where that people were going from HDF4 to GeoTiff.