Observational methods for stellar magnetism: from detection to cartography

Strassmeier Klaus, kstrassmeier@aip.de, AIP, Potsdam, Germany
Carroll Thorsten, tcarroll@aip.de, AIP, Potsdam
Ilyin Ilya, ilyin@aip.de, AIP, Potsdam

Abstract
We summarize new and old techniques to extract stellar magnetic field strengths from high-quality, high-resolution optical spectra. Our emphasis will be on spectral-line inversion techniques from Stokes spectropolarimetry to reconstruct the three-dimensional structure of surface magnetic fields of cool stars. The application potentials,the shortcomings, and the failures will be discussed in particular in correspondence to future instrumentation of future extremely large telescopes.