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GBTIDL Release Notes Version 1.2

• GBTIDL Release Notes Version 1.2
  • Introduction
  • Getting Started
  • Running GBTIDL in Green Bank or Charlottesville:
  • Running your own copy of GBTIDL
    • IDL License
    • Download and Installation of GBTIDL
  • New Features
  • Bug Fixes
  • New User Contributed Code
  • Known Issues
  • Future Plans

Introduction

We are pleased to announce the release of GBTIDL, version 1.2. GBTIDL is an interactive package for reduction and analysis of spectral line data taken with the Robert C. Byrd Green Bank Telescope. The package consists of a set of straightforward yet flexible calibration, averaging, and analysis procedures (the "GUIDE layer") modeled after the UniPOPS and CLASS data reduction philosophies, a customized plotter with many built-in visualization features, and Data I/O and toolbox functionality that can be used for more advanced tasks. The entire package is written in IDL.

GBTIDL version 1.2 contains numerous new features and bug fixes, as described in these release notes.

Getting Started

• The starting point for GBTIDL documentation, bug reporting and tracking, and discussion is here: http://gbtidl.nrao.edu/

Running GBTIDL in Green Bank or Charlottesville:

• At the unix prompt, simply type 'gbtidl'

Running your own copy of GBTIDL

IDL License

• You must have an IDL license to run GBTIDL. IDL version 6.0 and later is supported. If you don't have a license you can run GBTIDL remotely, using the computers in CV or GB. See the GBTIDL homepage for details.

Download and Installation of GBTIDL

• To obtain GBTIDL, download the files here
• Create a directory for the installation and unzip the tar ball:

    mkdir mygbtidl
    mv gbtidl-1.2.tar.gz mygbtidl/.
    cd mygbtidl
    gzip -d gbtidl-1.2.tar.gz
    tar -xvf gbtidl-1.2.tar

• go to the top level directory, 'gbtidl':

    cd gbtidl

• copy 'run_gbtidl' to 'gbtidl':

    cp run_gbtidl gbtidl

• edit the 'gbtidl' script to replace "PLACE_INSTALLATION_DIR_HERE" with the full path to the gbtidl executable script. It should then look something like this:

    export GBT_IDL_DIR=/home/mygbtidl/gbtidl

• start the package by calling the script 'gbtidl':

    ./gbtidl

• You may wish to add the installation directory to your unix path.

New Features

• Uses IDL 6.2, which includes improved help features and persistent command-line history buffers.
• GBTIDL procedures and plotter are now robust in continuum mode. If a procedure cannot handle continuum data yet, a message is printed.
  • Use line and cont to toggle between line and continuum mode.
• New columns in the index file for spectral line data:
  • TIMESTAMP: identifies when a scan was observed, and can be used to uniquely identify scans, even when identical scan numbers are used.
  • FREQRES: represents the backend's frequency resolution
  • FREQINT: replaces the former RESOLUTION, and is the absolute value of the backend's channel spacing (frequency_interval)
• New fields in the spectrum data container: 'timestamp' and 'frequency_resolution'
• New commands:
  • gconvol convolve a spectrum with an arbitrary array
  • gsmooth convolve a spectrum with a Gaussian to achieve a desired frequency resolution
  • resample resample a spectrum with a different channels spacing
• New optional keywords in existing commands:
  • scan_info: /quiet
  • ave: wtarray, /count
  • gshift: /linear, /quadratic, /lsquadratic, /spline, /cubic
  • getbs, getfs, getnod, getps, getsigref, gettp: /keepints, /quiet, status
  • decimate: startat, buffer, ok
  • hanning: ok
  • replace: /blank
• The /noweight keyword in the calibration routines is now called /eqweight (relevant to getbs, getfs, getnod, getps, getsigref, and gettp).
• New optional histogram-style plots in the plotter accesible via the histogram procedure.
• Proper handling of IEEE Not-A-Number (NaN) values in data (data blanking).
• Automatic weighting in accum and ave takes into account frequency_resolution.
• boxcar, hanning, and gsmooth adjust frequency_resolution to estimate new resolution after smoothing.
• Some documentation improvements

Bug Fixes

• Index File now handles maximum size of scan number, subscan number, and extension row number.
• Index File now handles file names of up to 64 chars, though only 32 are displayed when using list.
• New TIMESTAMP value in Sdfits used when creating index file - fixes bug associated with identical scan numbers in the same project.
• Keep file now correctly stores the value of the CAL column.
• Keep file now also stores PLNUM and FDNUM columns so that these values are retained properly in the case of index recreation.
• filein now correctly recovers when passed the wrong type of fits file (a spectral line file when in continuum mode, for instance).
• Data Container fields 'longitude_axis' and 'latitude_axis' are no longer assumed to be RA and DEC.
• accum no longers alters weight argument, even when unset. accum can now be safely used within a procedure as a result.

New User Contributed Code

• abbrev is a group of procedures that provide abbreviations for some of the longer gbtidl command names. Run abbrev to see the list of abbreviations. For example, "emptystack" becomes "es", "addstack" becomes "as", "setregion" becomes "sr", etc.

Known Issues

• TIMESTAMP selection is not yet available from the calibration routines (getbs, getfs, getps, getnod, getsigref, and gettp). Consequently, duplicate scan numbers in the same data file will confuse these routines.

Future Plans

• We encourage you to provide feedback. Comments and requests from users of GBTIDL version 1.2 will be incorporated into future versions.

-- BobGarwood - 17 Nov 2005