
<change id=0098>
 <author> Ger van Diepen </author>
 <date> 2001/06/11 </date>
 <avers> 1.6 </avers>
 <area> Library </area>
 <package> ms </package>
 <module> MeasurementSets </module>
 <type> Code </type>
 <category> New </category>
 <defects>  </defects>
 <summary>
Data compression is now possible
 </summary>
 <description>
The function addColumnCompression has been added to MSTable.
It makes it possible to define in the MS table description that
compression has to be used for the given column (using the new
virtual column engines CompressFloat or CompressComplex).
It can only be used for Float or Complex columns (which get compressed
to Short and Int, resp.).
It means that 3 extra columns get added: X_COMPRESSED, X_SCALE, X_OFFSET
where X is the name of the original column.
One can choose the let the engine scale automatically or to supply a
scale and offset values before putting the data.
Note that compression is only meaningful for bigger arrays. If e.g.
nchan==1, compression is not useful at all.
The MS constructor recognizes from the TableDesc that compression is
required and will set up the data managers accordingly.

In order to use compression fillers need to be changed.
The code to use compression in a filler is e.g.:
    TableDesc td(MS::requiredTableDesc());
    // Add the DATA column and compress it.
    MS::addColumnToDesc(td, MS::DATA, 2);
    MS::addColumnCompression (td, MS::DATA);
    SetupNewTable setup(msName, td, Table::New);
    MeasurementSet ms(setup);
 </description>
</change>

<change id=0099>
 <author> Athol Kemball </author>
 <date> 2001/06/25 </date>
 <avers> 1.6 </avers>
 <area> Tool </area>
 <package> ms </package>
 <module> fitsidi2ms </module>
 <type> Code </type>
 <category> New </category>
 <defects>  </defects>
 <summary>
New FITS-IDI filler tool
 </summary>
 <description>

The existing FITS-IDI filler code has been rationalized to
include contributed code from Tak Tsutsumi (CfA), which
supports a greater range of FITS-IDI subtables and multiple
UV_DATA extents. The older fitsidi2ms.cc stand-alone
program has also been converted to an AIPS++ DO fitsidi2ms.g.
 </description>
</change>

<change id=0108>
 <author> Raymond Plante </author>
 <date> 2001/10/25 </date>
 <avers> 1.6 </avers>
 <area> Library </area>
 <package> ms </package>
 <module> MeasurementSets </module>
 <type> Code </type>
 <category> Bugfix </category>
 <defects> AOCso02280 </defects>
 <summary>
Properly support -1 (wildcard) indicies according to MS2 spec.
 </summary>
 <description>
This change fixed a bug that is seen when certain MS subtables (SOURCE,
FEED) make use of the -1 wildcard index for SPECTRAL_WINDOW_ID.  It 
prevented imager from properly matching rest frequencies to spectral 
windows, causing data selection by velocity to fail.
 </description>
</change>
