A system and method for reducing transfer latencies in fencepost buffering requires that a cache is provided between a host and a network controller having shared memory. The sensor has a peg projecting from said flat piece. Error values are generated indicative of error between the measured data points and the full-space polynomial model. An overlay error is obtained from the overlay target by analyzing the image information or the intensity signal of the overlay target. The arrangement enables the operator to clearly know how a verifying action is being executed for confirming whether or not the actually used recording apparatus can be remotely operated by the reproducing apparatus, how the editing work is progressing and how the reproducing apparatus is operating.