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Submitter: Ger van Diepen
Description: As described in the AJDI of August 11th, the AIPS++ project has delivered several highly valued components. One such component is the MeasurementSet, which nowadays is the de facto standard data format for visibility data. It is used by software packages such as CASA, MeqTrees, ASKAPSoft and LOFAR and in use at many institutes.

The first version of the MeasurementSet was defined in 1996 by Mark Wieringa (CSIRO) and Tim Cornwell (NRAO). In 2000 it was revised by Athol Kemball (NRAO) and Mark Wieringa.
The MeasurementSet v2.0 is described in Casacore note 229. It is a relational database-like data structure consisting of a main table containing the visibilities and some meta data. Several index fields refer to meta data in subtables such as ANTENNA. The table structure and some data fields in the tables are shown in the image. Also some LOFAR-specific tables are shown.
Care was taken that the format is easily extendible with instrument-specific tables and columns. In that way instrument-specific software can take advantage of these tables and columns, while general software such as CASA can still operate on the same MeasurementSet.

The MeasurementSet component is part of the Casacore package (see AJDI of June 5th, 2015). It is built on top of a few other Casacore components, in particular the Tables and the Measures. It was already mentioned in the AJDI OF August 11th that Dutch people played an important role in developing the AIPS++ software. This is certainly true for the MeasurementSet: Mark Wieringa has written most of the MeasurementSet code, Wim Brouw wrote the Measures code and Ger van Diepen the Tables code.

The wide adoption of the Measurement Set can be seen as one of the biggest successes of the AIPS++ project. In fact, a successor to the Measurement Set is being conceived that will also serve the next generation radio telescopes.
Copyright: Casacore
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