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DerivedMC.h
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1 //# DerivedMC.h: Derived MS and CalTable columns
2 //# Copyright (C) 2010
3 //# Associated Universities, Inc. Washington DC, USA.
4 //#
5 //# This library is free software; you can redistribute it and/or modify it
6 //# under the terms of the GNU Library General Public License as published by
7 //# the Free Software Foundation; either version 2 of the License, or (at your
8 //# option) any later version.
9 //#
10 //# This library is distributed in the hope that it will be useful, but WITHOUT
11 //# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 //# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
13 //# License for more details.
14 //#
15 //# You should have received a copy of the GNU Library General Public License
16 //# along with this library; if not, write to the Free Software Foundation,
17 //# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
18 //#
19 //# Correspondence concerning AIPS++ should be addressed as follows:
20 //# Internet email: aips2-request@nrao.edu.
21 //# Postal address: AIPS++ Project Office
22 //# National Radio Astronomy Observatory
23 //# 520 Edgemont Road
24 //# Charlottesville, VA 22903-2475 USA
25 //#
26 //# $Id$
27 
28 #ifndef DERIVEDMSCAL_DERIVEDMC_H
29 #define DERIVEDMSCAL_DERIVEDMC_H
30 
31 #include <casacore/casa/aips.h>
33 
34 namespace casacore { //# NAMESPACE CASACORE - BEGIN
35 
36 // <module>
37 //
38 // <summary>
39 // Derived MS and CalTable columns
40 // </summary>
41 
42 // <prerequisite>
43 // <li> <linkto module="MeasurementSets:description">MeasurementSets</linkto> module
44 // </prerequisite>
45 //
46 // <reviewed reviewer="" date="" demos="">
47 // </reviewed>
48 
49 // <etymology>
50 // Class to handle derived columns in an MS or CalTable.
51 // </etymology>
52 //
53 // <synopsis>
54 // A MeasurementSet or CalTable can be extended with virtual columns to
55 // be able to use hourangle, azimuth/elevation, parallactic angle, and UVW
56 // as if they were stored in the table using the DerivedMSCal virtual column
57 // engine. Such columns have a fixed name, otherwise the engine cannot handle
58 // them. The class description of the engine shows which columns can be handled
59 // and gives an example how to add them.
60 //
61 // Class UDFMSCal contains TaQL user defined functions for these virtual
62 // columns. In this way the columns do not need to be added to the table,
63 // but can be used directly in a TaQL command. For example:
64 // <srcblock>
65 // select from my.ms where derivedmscal.ha1() > 10deg
66 // </srcblock>
67 // to select the rows where the hourangle of ANTENNA1 fulfills the condition.
68 // If HA1 was added as a virtual column (which is more intrusive), the
69 // command could look like:
70 // <srcblock>
71 // select from my.ms where HA1 > 10deg
72 // </srcblock>
73 //
74 // UVW coordinates are already stored in an MS, but the virtual UVW_J2000
75 // column makes it possible to calculate them on the fly.
76 //
77 // An MS or CalTable can be created with one or more of these columns or they
78 // can be added later using 'DerivedMSCal' as their data manager.
79 // A column can, of course, also be removed. If all these columns are removed,
80 // the Table System will also remove the data manager from the table.
81 //
82 // The derivedmscal library can be used in two ways:
83 // <ol>
84 // <li> It needs to be linked in if the DerivedMSCal class is used. This
85 // mode will probably be used rarely.
86 // <li> It will be loaded dynamically when a table is opened with columns
87 // using this data manager, when a column is added to a table using
88 // this data manager by name (thus without an object), or when
89 // such a TaQL user defined function is used.
90 // </ol>
91 // <note> For the second reason above it is important that the library
92 // and the other casacore libraries are built shared.
93 // </note>
94 // </synopsis>
95 //
96 // <motivation>
97 // It is very handy to be able to use a column like PA in software that can
98 // deal with various table columns (e.g. TaQL, TablePlot, pyrap).
99 // </motivation>
100 
101 //# <todo asof="1997/02/01">
102 //# </todo>
103 
104 // </module>
105 
106 
107 } //# NAMESPACE CASACORE - END
108 
109 #endif