- the SeaWiFS Standard Mapped Products are already geocoded in WGS84 so should be easy to load into a lat/lon location with (at least this is true for PAR maps).
In some data I worked with, NULL was represented by -32767. This can be cleaned up using themodule:
MAP=S2010235.L3m_DAY_CHL_chlor_a_9km r.null $map setnull=-32767
Inspecting the HDF file with "gdalinfo" tell us that this data has a slope of 1 and intercept of 0, so does not need to be processed with.
You can download some preprocessed color rules for Chlorophyll-a from the GRASS addons SVN (based on NASA's GSFC OceanColor website's rules) and apply them with themodule.
r.colors $map rules=~/grass_addons/palette_chl_etc.gcolors
or use a simple equalized histogram to spread the colors to where the data is:
r.colors $map color=bcyr -e