1. An improved method of calibrating a vector network analyzer of the type that performs measurements over a user specified measurement frequency range less than a total frequency range for the vector network analyzer in discrete frequency steps and corrects the measurements using calibration data generated from reference impedances comprising the steps of: storing sparse calibration data over a calibration frequency range of the vector network analyzer as the calibration data, the calibration frequency range being greater than the user specified measurement frequency range; for each measurement by the vector network analyzer interpolating detailed system error data from the sparse calibration data; and using the detailed system error data to correct each measurement to provide calibrated measurements.