  Local percolation probabilities are used to characterize the connectivity in
porous and heterogeneous media. Together with local porosity distributions they
allow to predict transport properties \cite{hil91d}. While local porosity
distributions are readily obtained, measurements of the local percolation
probabilities are more difficult and have not been attempted previously. First
measurements of three dimensional local porosity distributions and percolation
probabilities from a pore space reconstruction for a natural sandstone show
that theoretical expectations and experimental results are consistent.
