Re: [ferret_users] Is it possible to use 'HDF Format' data fileinFerret?

[Virginia Kalb <Virginia.L.Kalb@xxxxxxxx>]

Hi,
  I am a novice ferret user, and can't even get started because I can't 
open my data set. I am accessing an HDF data set from a DODS server, as 
suggested:
______________________________________________________________________
[gk@whiterabbit ~]$ ferret
        NOAA/PMEL TMAP
        FERRET v5.81
        Linux(g77) 2.4.21-32 - 07/14/05
         3-Apr-06 13:07

yes? use 
"http://whiterabbit:2001/cgi-bin/nph-dods/hdf/MOD04_L2.A2000055.1020.005.2005351193906.hdf";
yes? show data
     currently SET data sets:
    1> 
http://whiterabbit:2001/cgi-bin/nph-dods/hdf/MOD04_L2.A2000055.1020.005.2005351193906.hdf 
 (default)
 name     title                             I         J         K 
        L

yes?
_______________________________________________________________________

so it looks like ferret is unable to import the data. The DAS file for 
this data set does have Latitude and Longitude attributes:
_______________________________________________________________________
[gk@whiterabbit ~]$ getdap -a 
"http://whiterabbit:2001/cgi-bin/nph-dods/hdf/MOD04_L2.A2000055.1020.005.2005351193906.hdf"; 
| more
Attributes {
    HDF_GLOBAL {
        String HDFEOSVersion "HDFEOS_V2.9";
        Int32 Number_of_Instrument_Scans 203;
        Int32 Maximum_Number_of_1km_Frames 1354;
        String title "\\012 MODIS HDF File Specification MOD04_L2: 
MODIS Level 2 Aerosol over Land and  \\012 Ocean Product
                          \\012";
...
...
    Longitude {
        String long_name "Geodetic Longitude";
        String units "Degrees_east";
        Float64 scale_factor 1;
        Float64 add_offset 0;
        String Parameter_Type "MODIS Input";
        Int32 Cell_Across_Swath_Sampling 5, 1345, 10;
        Int32 Cell_Along_Swath_Sampling 5, 2025, 10;
        String Geolocation_Pointer "Geolocation data not applicable";
        Float32 _FillValue -999;
        Float32 valid_range -180, 180;
    }
    Longitude_dim_0 {
        String name "Cell_Along_Swath:mod04";
    }
    Longitude_dim_1 {
        String name "Cell_Across_Swath:mod04";
    }
    Latitude {
        String long_name "Geodetic Latitude";
        String units "Degrees_north";
        Float64 scale_factor 1;
        Float64 add_offset 0;
        String Parameter_Type "MODIS Input";
        Int32 Cell_Across_Swath_Sampling 5, 1345, 10;
        Int32 Cell_Along_Swath_Sampling 5, 2025, 10;
        String Geolocation_Pointer "Geolocation data not applicable";
        Float32 _FillValue -999;
        Float32 valid_range -90, 90;
    }
    Latitude_dim_0 {
        String name "Cell_Along_Swath:mod04";
    }
    Latitude_dim_1 {
        String name "Cell_Across_Swath:mod04";
    }
...
...
___________________________________________________________________

Any ideas as to why I can't use this data set with ferret? Does anyone 
know of an OPeNDAP client that will read HDF data from an OPeNDAP 
server? All suggestions would be greatly appreciated.

  Thanks in advance,
     Ginny

 Ansley wrote:
> Hi all,
> Ferret can read HDF files only by using the HDF-reading capabilities    
> of DODS, that is if the file can be put on a DODS server.
>
> Now, Ferret will be successful in reading the file only if the HDF file 
> is similar in its structure to a COARDS or CF netCDF file. So, if the 
> file can be put on a DODS server, then Ferret can open it. Often, you 
> will need to apply the USE/ORDER= qualifier to change the ordering of 
> the coordinate axes.
>
> If a file is on a DODS server, you can look at the DAS in your browser 
> (the URL that ends in .das). When you look at the attribute data check 
> to see if there are dimension variables with attributes that look like a 
> Latitude or Longitude as in the COARDS conventions.
>
> Here is a message from the Users List about another possible way to 
> access such files
> http://ferret.pmel.noaa.gov/Ferret/Mail_Archives/fu_2005/msg00444.html
>
> Ansley
>
> C. Shaji wrote:
>
>     Dear All,
>     I would like to know if it is possible to use the 'hdf format' data 
> file
>     in Ferret. When I load it, it gives the error as it is not a netcdf 
> file.
>     Can someone suggest me how can use this file in Ferret for plotting?
>
>     NOAA/PMEL TMAP
>     FERRET v5.51
>     Linux 2.4.3-12smp - 03/05/03
>     29-Mar-06 11:10
>
>     yes? use month01_combined.hdf
>     ** netCDF error: Not a netcdf file
>     is this a CDF file ?
>
>     Thanks in advance,
>
>     C. Shaji.