Data analysis techniques for stereo IACT systems

Based on data and Monte-Carlo simulations of the HEGRA IACT system, improved analysis techniques were developed for the determination of the shower geometry and shower energy from the multiple Cherenkov images. These techniques allow, e.g., to select subsamples of events with better than 3’ angular resolution, which are used to limit the rms radius of the VHE emission region of the Crab Nebula to less than 1.5’. For gamma-rays of the Mrk 501 data sample, the energy can be determined to typically 10% and the core location to 2-3 m.