  The diffusive shock acceleration scenario is usually invoked to explain radio
relics, although the detailed driving mechanism is still a matter of debate.
Our aim is to constrain models for the origin of radio relics by comparing
observed relic samples with simulated ones. Here we present a framework to
homogeneously extract the whole sample of known radio relics from NVSS so that
it can be used for comparison with cosmological simulations. In this way, we
can better handle intrinsic biases in the analysis of the radio relic
population. In addition, we show some properties of the resulting NVSS sample
relics such as the correlation between relic shape and orientation with respect
to the cluster. Also, we briefly discuss the typical relic surface brightness
and its relation to projected cluster distance and relic angular sizes.
