  Measurements on a subset of the boundary are common in electrical impedance
tomography, especially any electrode model can be interpreted as a partial
boundary problem. The information obtained is different to full-boundary
measurements as modeled by the ideal continuum model. In this study we discuss
an approach to approximate full-boundary data from partial-boundary
measurements that is based on the knowledge of the involved projections. The
approximate full-boundary data can then be obtained as the solution of a
suitable optimization problem on the coefficients of the Neumann-to-Dirichlet
map. By this procedure we are able to improve the reconstruction quality of
continuum model based algorithms, in particular we present the effectiveness
with a D-bar method. Reconstructions are presented for noisy simulated and real
measurement data.
