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We discuss spectropolarimetric measurements of photospheric (Fe I 630.25 nm)and chromospheric (Ca II 854.21 nm) spectral lines. Our long-term goal is todiagnose properties of the magnetic field near the base of the corona. Wecompare ground-based two-dimensional spectropolarimetric measurements with(almost) simultaneous space-based slit spectropolarimetry. The ground-basedobservations were obtained May 20, 2008, with IBIS in spectropolarimetric mode,The space observations were obtained with the Spectro-Polarimeter aboard theHINODE satellite. The agreement between the near-simultaneous co-spatial IBISand HINODE Stokes-V profiles at 630.25 nm is excellent, with V/I amplitudescompatible with to within 1 %. IBIS QU measurements are affected by residualcrosstalk from V, arising from calibration inaccuracies, not from any inherentlimitation of imaging spectroscopy. We use a PCA analysis to quantify thedetected cross talk. Chromospheric magnetic fields are difficult to constrainby polarization of Ca II lines alone. However, we demonstrate that highcadence, high angular resolution monochromatic images of fibrils in Ca II andH-alpha, can be used to improve the magnetic field constraints, underconditions of high electrical conductivity. Such work is possible only withtime series datasets from two-dimensional spectroscopic instruments underconditions of good seeing.

Fabry-Perot versus slit spectropolarimetry of pores and active network. Analysis of IBIS and Hinode data