1 History

The Global Section Datafile (GSD) subroutine library package was written in 1987 by Jon Fairclough [1] to permit the fast reading and writing of data at the James Clerk Maxwell Telescope. Development was stimulated by the need to provide fast filing of data in the so-called “General Single Dish Data” (GSDD) format developed by MRAO, IRAM and NRAO. The JCMT used the GSD format for data storage from all instrumentation until the arrival of SCUBA [2] in 1996 (which uses NDF [3]) and data files in this format will continue to be written by the heterodyne system until the delivery of ACSIS in 2001.

The original GSD I/O library was written in VAX Fortran and has never been ported to a Unix environment. With the move from VMS to Unix in 1994/1995 it was clear that a version of the GSD library was required that would be able to read GSD files (those in the archive as well as new files) without having to change the existing telescope acquisition system or require the use of a VMS application to convert the format on demand. A read-only version of the library was written in C by Remo Tilanus and Horst Meyerdierks in 1994 and was incorporated into the Starlink releases of JCMTDR [4] and SPECX [5].