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sdsfits - convert selected plane or coordinate descriptor of SDS HDF4 to FITS


sdsfits [parameter=value]


sdsfits converts an hdf(1) SDS dataset into fits(5NEMO) image format. The current version was written to fit a particular purpose, and will only properly convert a single 2D or 3D SDS dataset into a FITS image/cube. Selection must be made wich SDS dataset is converted (1=first) and optional the coordinate values can be written instead of the SDS values. The fitsbrowser toolset in HDF can also convert SDS from/to a FITS file (primary HDU). One can also reorder the axes in the data matrix/cube, albeit at a cost.


The following parameters are recognized in any order if the keyword is also given:
Input file (SDS HDF file)
Optional output FITS file. If no filename given, the input dataset is merely scanned and it’s rank and size are reported.
Select a file_number (1 being the first) for output. Currently only one fits file at a time can be extracted. [Default: 1].
If non-zero, this coordinate axis will be dumped as a 1D array in the fits file. Note the first axis is the one that described the fasted running index in the data-array (i.e. fortran array notation). A 0 is used if the 2/3D array is written. Default: 0.
Reorder the axes. Normally the data is transferred to the FITS file "as is", without reordering, though SDS lists the axis backwards (NZ,NY,NX: where NX is the fastest running axis in fortran sense, and in FITS normally plotted horizontally). With reorder=t all data is reordered, which can take large resources for large SDS files.
Write dummy axis that have dimension 1 also? [Default: t]
Add a WCS to the fits file, as much as that is possible. By default (there is no keyword to change this yet) the first pixel (1,1,1) will be the reference pixel, and CDELT will be computed by the difference to the 2nd pixel along the appropriate axis. If there is no 2nd pixel, CDELT will be 1. If there is a 3rd pixel and the CDELT is different, a warning is posted. [Default: t]


No known bugs, but there are some limitations in the current version:

1) input SDS must be a 2D or 3D - output will be the corresponding FITS image map/cube

2) the whole SDS is read into memory, no slicing. Although this is fast, it limits the size of the cube to the (virtual) memory you have.

3) Only the required FITS header keywords NAXIS, NAXIS1, NAXIS2 and NAXIS3 are written out.

See Also

snaphdf(1NEMO) , hdf(1) , lshdf(1) , fitssds(1NEMO) , tsd(1NEMO) , fits2sds(1HDF) , phdu2sds(1HDF) (fitsbrowser::fits2sds,phdu2shs)


The hdf format described here is the old classical "hdf4" format, not the new "hdf5" format. Within HDF there are many "dialect", in particular the so-called Multifile Scientific Data Set (SD) and Single-File Scientific Data Set (DFSD).


In this example the file hdf100bg has 3 SDS datasets of 19 cells in Y, and 32 cells in X each.
% tsd hdf100bg
Found 3 scientific data sets in hdf100bg
1: R-VELOCITY AT TIME=2.00E+00(19,32) km/sec  -> [608 elements of type: 5 (FLOAT32)]
2: PHI-VELOCITY AT TIME=2.00E+00(19,32) km/sec  -> [608 elements of type: 5
3: DENSITY AT TIME=2.00E+00(19,32) Msolar/pc**2  -> [608 elements of type:
5 (FLOAT32)]
% sdsfits hdf100bg map1.fits 3 reorder=f
Data: DENSITY AT TIME=2.00E+00 Msolar/pc**2 1pe8.2 Polar
map1.fits: writing as FITS file
Data min/max = 0.00177725 362.925
% sdsfits hdf100bg map2.fits 3 reorder=t
Data: DENSITY AT TIME=2.00E+00 Msolar/pc**2 1pe8.2 Polar
map2.fits: writing as FITS file
reorder: 19 x 32
Data min/max = 0.00177725 362.925



Peter Teuben

Update History

19-Jan-95    V1.0 Created     PJT
13-apr-95    V1.1 added select=, fixed bug in 2D conversion    PJT
13-apr-96    V1.2 added axis=    PJT
14-jan-03    V1.4 added reorder=    PJT
2-dec-04    V1.5 added dummy=, and fixed some 3D data bugs    PJT
11-dec-04    V1.6 added wcs=, fixed some more bugs with 3D data        PJT

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