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GPItv Viewer User’s Guide

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Starting GPItv

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Purpose of GPItv

GPItv is a data viewer tool that provides GPI observers with both a simple means for cursory “quick look” data analysis, in real time at the telescope, and a sophisticated set of tools for viewing and manipulating GPI data during post-observing scientific analyses. GPItv includes features for spectral and polarimetric analyses of raw 2D and/or processed 3D data from GPI. GPItv should help you to look at GPI data in a way that enables you to get your science done.

GPItv is a heavily customized derivative from ATV, the well-known DS9-like display tool for astronomical images in IDL (Barth et al. 2001;, with much new functionality developed specifically for GPI. Anyone familiar with using ATV, SAOimage or DS9 will get used to GPItv very quickly.

One significant enhancement relative to the original ATV program is that GPItv’s internals have been rewritten to allow multiple copies to run simultaneously. Thus users can view for instance raw frames, reduced datacubes, and ADI-processed subtracted images all in separate windows simultaneously

Summary of Functionality: Image Manipulation and Data Analysis

GPItv is a display tool that includes features for image analysis and spectral analysis. 2D image analysis tools are available for image manipulation, including:

  • Display of 2D/3D images with a variety options for scaling, color map, color stretch, zoom, and rotation.
  • World coordinate system information (X,Y,lambda) is displayed when appropriate keywords are available in the image header.
  • Viewing and editing image FITS headers
  • Quick photometry and image statistics
  • Image output in a variety of formats (FITS, PS, JPEG, PNG, & more)
  • Labeling and overplots to annotate images
  • Display of radial line plots, surface plots, and histograms of data regions
  • Image blinking
  • Automatic detection of new fits image in chosen directories
  • High-contrast AO contrast assessments

Spectral analysis tools include:

  • Multi-plane image slider for datacubes
  • Extraction of 1D spectra from chosen regions
  • Spectral plotting
  • Display and verification of the wavelength solution
  • Collapse datacube
  • Simple difference Imaging

Polarimetric analysis tools include:

  • Display of polarized datacubes in both Stokes IQUV and perpendicular polarization pair formats
  • Overplotting of polarization vectors, with many configurable options
  • Computation of total intensity, polarized intensity, & polarization fraction from IQUV datacubes.

New features can be added to GPItv easily, including linking to or calling existing IDL programs. For example, you can easily define a keyboard shortcut that will pass the current cursor position in data coordinates to an external IDL routine.