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PTB develops primary standard capable of measuring distances up to 1 km with sub-millimetre accuracy

As part of EMRP project Metrology for long distance surveying (SIB60 Surveying), a novel primary standard for the calibration of geodetic reference baselines was developed by PTB. The TeleYAG system is capable of measuring distances up to 1 km optically with sub-millimetre accuracy. Aside from a measurement of humidity, the device does not require information from auxiliary sensor systems like a temperature sensor network. 

The device was successfully demonstrated in a verification experiment performed at one of the best reference baselines in Nummela, Finland. The device offers, for the first time, high-accuracy traceability to the SI definition of the metre for the most common verification approach used by surveyors worldwide.