  Precise positioning measurement plays an important role in in today advanced
manufacturing industry, and length traceability chain has been optimizing and
enriching to fulfill the developing and various precise positioning
requirement. In this paper, we propose a new length traceability chain based on
chromium atom transition frequency, which is a combining utilization of
fundamental physical constant accuracy and grating interferometer environmental
robustness. The selftraceable grating pitch standard, the selftraceable angle
standard and the selftraceable grating interferometer are promising to improve
the measurement accuracy, consistency and selfcalibration ability in situ for
precise positioning.
