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Improving the traceability chain in geodetic length measurements by the new robust interferometer TeleYAG

A novel primary standard for the calibration of geodetic baselines, the “TeleYAG” interferometer is being developed in the European Joint Project EMRP SIB60 ''Metrology for long distance surveying”. The optical distance measurement is realized as an absolute measuring heterodyne interferometer with a targeted measuring range of 1 km and an accuracy of 0.1 mm or better. To achieve such a measurement uncertainty outdoor, the index of refraction must be determined with an uncertainty of 0.1 ppm. Hence, the interferometer has to compensate for the influence of the index refraction in-situ by implementation of the dispersion-based two-color measurement method. In addition, particular focus was on the mechanical stability of the measurement head. The measurement principle, the device design, and first indoor verification results with this interferometer at the 50 m interference comparator of the PTB will be presented in this paper.

traceability ; refractive index compensation ; multi-wavelength interferometry ; surveying ; geodesy

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