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Introduction The development of optical clocks that can be transported and operated outside metrologylaboratories promises exciting new and competitive measurement methods for geodesy,where chronometric levelling is considered as a complementary method to measure heightdifferences [1-4]. To perform such tasks in a competitive way, it is not sufficient to demonstrate the clockperformance in the laboratory, but transportable clocks need to show reproducibility of theirfrequency at the level of few parts in 1017 and better in the various locations to which they aretransported and where they are used. At Physikalisch-Technische Bundesanstalt (PTB), we have developed such atransportable optical clock [5] that has been tested for the applications described above bymeasurement campaigns outside the laboratory. Here we present the latest of thesemeasurement campaigns (Fall 2018) performed at the Max Planck Institute of QuantumOptics (MPQ), discuss the clock´s current uncertainty budget, and recent hardwareupdates. Measurements between Braunschweig and Garching For our recent experiment, we transported the clock to MPQ in Garching (Munich), fromwhere a ∼940 km fiber link allowed us to compare the transportable clock’s frequency viafrequency combs to the 87Sr lattice [6] and Yb+ single ion [7] clocks in our laboratory atPTB in Braunschweig. Because no other atomic clock at this level of stability and accuracy isavailable for calibrating the system in the research facility (MPQ), we can clearlydemonstrate the use of transportable optical clocks outside the usual metrology laboratoryconditions. With upgraded hardware, we improved the clock’s uptime shown during theprevious campaign, while at the same time reducing the time needed to set it up. Theachieved uncertainty is dominated by the systematic uncertainty of the transportable clock offew parts in 1017, corresponding to a few tens of centimeters on the height difference betweenboth sites. The limitation on this uncertainty will be discussed. The height difference betweenthe two locations has also been measured independently with state-of-the art geodeticmethods [4]. Results Through the experiment and results presented in this paper we demonstrate the currentstatus of PTB’s transportable clock, in view of reaching a trustworthy reproducibility of itsfrequency at the low 10−17 uncertainty level together with high reliability and uptime duringmeasurement campaigns. We reach this resolution of a few decimeters in height within threehours of integration time. At this level of accuracy, it is in fact possible to performchronometric leveling measurements, and with further improvements, these maybecome competitive to classical geodesy methods. We will also our plan to overcomethem in view of chronometric levelling measurements at the centimeter level ofaccuracy. References A. Ludlow, Nature Phys. 14, 432-432 (2018) T. Mehlstäubler et al., Rep. Prog. Phys 81, 064401 (2018) J. Grotti et al., Nature Phys. 14, 437 (2018) H. Denker et al., J. Geod. 92, 487 (2018) S. B. Koller et al., Phys. Rev. Lett. 118, 073601 (2017) C. Grebing et al., Optica 3, 563 – 569 (2016) N. Huntemann et al., Phys. Rev. Lett. 116, 063001 (2016) [ABSTRACT FROM AUTHOR]