Since 2016 a DORIS beacon is operated at the geodetic observatory Wettzell. The main goal is the co-location with the other geodetic space techniques Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR) and Global Navigation Satellite Systems (GNSS). The local ties between the reference points of the space techniques are usually obtained with formal errors after the adjustment of less than 1 mm. Even if the instrument is well calibrated, the accuracy may be degraded by refraction errors due to air density variations, or by a misalignment in the global frame after the coordinate transfomation.

These potential errors are tackled in the framework of the GeoMetre project. Different strategies to overcome the refraction problem, e.g. by using two color laser distance meters or integral temperature measurements along the line of sight, were developed and tested in the field. Other work packages deal with the datum problem and suggest a transformation-free approach by including additional observations like deviations of the vertical.

Applying these novel instruments and techniques, new sets of local ties were generated at the geodetic core stations Metsähovi and Wettzell. Accurate local ties are an important element to harmonize different solutions of geodetic reference frames and are the basis of the combination of the geodetic space techniques.