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13.6 The GILDAS implementation

We have now introduced the basic parameters of the imaging process: gridding, weighting and tapering. The main imaging task in the GILDAS software is UV_MAP. Before using UV_MAP, it is also recommended to use the associated task UV_STAT which evaluates the beam sizes, point source and brightness sensitivity as function of taper or robust weighting parameter.

Although the choice of configurations for the Plateau de Bure interferometer has been performed in order to optimize the uv coverage for most observing conditions, robust weighting can often offer a better compromise, unless signal to noise is insufficient. Task UV_STAT also suggests appropriate pixel sizes for UV_MAP

The imaging task UV_MAP is controlled by the following parameters:

The other parameters are used to re-center the map (by phase shifting the uv data before imaging) when needed. This is convenient for Mosaics. UV_MAP performs all the imaging steps presented before: gridding, weighting, tapering, correction for gridding function, and computes the dirty beam and dirty image.

Both UV_STAT and UV_MAP are implemented as commands in the MAPPING program, or as tasks available from the GRAPHIC program. Using one or the other is a matter of personal preference.


next up previous contents
Next: 13.7 Deconvolution Up: 13. The Imaging Principles Previous: 13.5 Weighing and Tapering
S.Guilloteau
2000-01-19