Approximation order of interpolatory nonlinear subdivision schemes

Linear interpolatory subdivision schemes of CrCr smoothness have approximation order at least r+1r+1. The present paper extends this result to nonlinear univariate schemes which are in proximity with linear schemes in a certain specific sense. The results apply to nonlinear subdivision schemes in Lie groups and in surfaces which are obtained from linear subdivision schemes. We indicate how to extend the results to the multivariate case.