When intrinsic volumes and Minkowski tensors of a real world structure are computed, this is often based on a digital image. The digitization causes some estimation problems due to the anisotropic nature of the digital grid. Even the most natural and frequently used algorithms based on counting the local pixel/voxel configurations are often biased. In this chapter, we survey the known results on convergence of these local algorithms with a focus on estimation of intrinsic volumes. Moreover, we present some of the latest attempts to define convergent algorithms.