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Paper: Image Analysis
Volume: 180, Synthesis Imaging in Radio Astronomy II
Page: 301
Authors: Fomalont, Ed B.
Abstract: Image analysis is the general term applying to those procedures and techniques which are used to interpret and parametrize information from an image or a set of images. These procedures also include obtaining error estimates for the derived parameters and estimating the image reliability. Image analysis is a vague term, and the choice of image analysis techniques is dependent on the nature of the observations and the type of questions which motivated the experiment. Nevertheless, some general analysis techniques are useful to discuss. The philosophies of most of the techniques will be emphasized, and implementation details will not be discussed except when necessary. VLA software will be mentioned in connection with specific algorithms. Here it is assumed that the set of images has been appropriately processed and is of good quality. For aperture synthesis, this processing includes data editing and calibration (Lecture 5), as well as deconvolution of the point spread function (Lecture 8) and self-calibration (Lecture 10), if necessary. Apart from those defects which are peculiar to aperture synthesis, much of the material of this lecture should be applicable to images from a variety of astronomical instruments. Image display is an important aid in image analysis. For simple images, grey-scale and color TV-oriented displays and contour diagrams are essential for determining the general features in the intensity distribution which are amenable to analysis. For complicated images, particularly sets of images over frequency, subtle and ingenious displays are required to perceive faint features and morphologies. Once recognized, these features can be analyzed and parametrized in a manner which is astronomically useful. Whenever a specific image analysis function is described in this lecture, the name of a computer implementation of that function, within the NRAO Astronomical Image Processing System (AIPS), will be mentioned also.
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