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Surveying and navigation became much easier, more accurate and operational thanks to the Global Positioning System. The use of this technology in height determination, bathymetry and 3-D navigation is not only limited by the reduced accuracy compared to the horizontal component. It supposes additional information about the geodetic height reference surface in order to leverage the full potential of this technology. The corresponding models, measurements and activities which are necessary to improve this part of the geodetic infrastructure are usually behind the curtain. This article emphasizes the need of a common cross-border geodetic infrastructure and the relevance of precise models of the height reference surface for GNSS-aided height determinations. The need of gravimetric surveys for the determination and improvement of these models is explained. Finally, it gives an overview about the gravimetric surveys which were carried out in the German Exclusive Zone of the North and Baltic Sea over more than one decade and provides some insight into practical aspects and challenges of this kind of surveys.

Gravity determination at sea is essential for the definition of physical height systems at sea and adjacent coastal areas. Since 2017, four shipborne gravimetry campaigns were conducted using a Chekan-AM gyro stabilized platform gravimeter containing quartz spring sensors and an iMAR Inertial Measurement Unit serving as strapdown gravimeter. The comparison of both gravimeter types exposed complementary properties of both sensors. With proper maintenance, the gyro stabilized gravimeter shows a very stable linear drift, but its recordings are impaired by steering manoeuvres and harsh sea conditions. In contrast, the strapdown gravimeter recordings are typically reliable during the whole cruise. But with up to 80 hours, the durations of some of the analysed cruises were exceptionally challenging for strapdown measurements. Under these conditions, the accuracy of the strapdown recordings is slightly degraded due to non-linear sensor drift, although the major part of the drift can be eliminated by thermal calibration or stabilisation. Under smooth sea conditions at the Baltic Sea with cruise durations of less than 35 hours, a precision of 0.4 to 0.5 mGal was obtained for both individual gravimeter results. A combination of both gravimeter types using complementary high- and low-pass filtering provided drift reduction and the possibility of gravity determination during the entire cruise. In the latest campaign, two strapdown gravimeters were installed in addition to the gyro stabilized platform gravimeter allowing for a detailed comparison of the drift behaviour of all three gravimeters., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

FAMOS (Finalizing Surveys for the Baltic Motorways of the Sea) is a recently run project which was supported by EU to improve the safety of ship navigation on the Baltic Sea. One task of FAMOS was to work on a common height reference for the Baltic Sea, the Baltic Sea Chart Datum 2000 (BSCD2000), which will be based on a new gravimetric geoid for this sea. The German institutions German Research Centre for Geosciences (GFZ), Federal Agency for Cartography and Geodesy (BKG), Federal Maritime and Hydrographic Agency (BSH) and Technical University of Darmstadt performed several marine gravimetry surveys to contribute to this project. The primary measurement equipment was GFZ’s Chekan-AM gravimeter. On two of these campaigns an iMAR strapdown inertial measurement unit (IMU) was used together with the Chekan. The data records from both instruments are of very good consistency. Since the FAMOS project ended ahead of the planned schedule already in 2019, finalization of the new chart Datum is now coordinated by the Chart Datum Working Group within the Baltic Sea Hydrographic Commission. It is planned to implement the new BSCD2000 by 2023.

Objective: State of the art intensive care for SAH and TBI patients relies to a certain degree on neuromonitoring data including local brain tissue pO2 measurements. Usually local pO2 probes are placed in the white matter around 2 cm below the cortex. Here we compare a opto-chemical method of planar[for full text, please go to the a.m. URL], 62. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit der Polnischen Gesellschaft für Neurochirurgen (PNCH)

Objective: The measurement of brain parenchyma pO2 is a valuable standard procedure for neurocritically ill patients. Here we utilize a opto-chemical method of planar oxygen detection for measuring changes of cortex pO2 during a reversibly introduced epidural mass lesion. Methods: 17 male wistar [for full text, please go to the a.m. URL], 61. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC) im Rahmen der Neurowoche 2010

Within the framework of the REAL GOCE project, one of the main objectives is the validation of the GOCE products. In this contribution, the focus is on the regional validation of the GOCE products by independent terrestrial data sets in Europe and particularly in Germany, including terrestrial gravity anomalies, height anomalies from the high-resolution gravimetric quasigeoid models EGG2008 and GCG05, and astrogeodetic vertical deflections. Differences between the terrestrial data sets and the available GOCE geopotential models, with envisaged accuracies of 1 mgal for gravity and 1-2 cm for geoid heights, both at a resolution of 100 km, are computed and analyzed. The progress with respect to the GRACE models and the impact on regional gravity field modelling is outlined.

Objective: The monitoring of oxygen supply to the brain is a challenge in advanced neuromonitoring of critically injured patients with TBI or SAH. It has been shown that poor neurological outcome is associated with a low ptiO2. Radial oxygen gradients over arterioles are of interest because they characterize[for full text, please go to the a.m. URL], 60. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit den Benelux-Ländern und Bulgarien

A regional geoid model for the Argentine part of the Isla Grande de Tierra del Fuego, established in previous works on the basis of GPS levelling, suffers a lack of observation data in the remote south-western investigation area. In order to improve the data distribution in this region, the mean lake level of Lago Fagnano has been regarded as a natural indicator for the local geoid. Using a GPS buoy and pressure tide gauges, a method to determine the mean lake surface topography with respect to the ellipsoid has been developed. It is shown that the obtained lake level geometry is essentially controlled by the regional gravity field. The derived information on the mean lake level has been included in the geoid model, which results in a more detailed and plausible representation of the regional geoid., Facultad de Ciencias Astronómicas y Geofísicas

BASEWECS is a contribution to the German Climate Research Program DEKLIM. The project started in May 2001 and lasted until December 2004. BASEWECS aimed at the investigation of the influence of the Baltic Sea and its annual ice coverage on the water and energy budget of the BALTEX area