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Surface ocean currents in polar regions can be monitored by satellite altimetry-derived geostrophic currents. However, they are characterized by an irregular and sparse data sampling. Therefore, novel methods like an unsupervised classification for detecting water areas within the sea ice area and a combination strategy based on a principal component analysis for linking ocean model output with an altimetry-derived ocean topography are developed to enable a consistent computation of ocean surface currents., Mit Hilfe von Satellitenaltimetrie abgeleiteten geostrophischen Strömungen können Oberflächen-Meeresströmungen in polaren Regionen beobachtet werden. Jedoch zeichnen sich diese durch eine unregelmäßige und lückenhafte Datenverteilung aus. Neuartige Verfahren zur Detektion von Wasserflächen innerhalb des Meereises und zur Kombination der beobachteten dynamischen Ozeantopographie mit einem Ozeanmodell unter Verwendung einer Hauptkomponentenanalyse, erlauben eine konsistente Berechnung von Oberflächen-Meeresströmungen.

Surface ocean currents in polar regions can be monitored by satellite altimetry-derived geostrophic currents. However, they are characterized by an irregular and sparse data sampling. Therefore, novel methods like an unsupervised classification for detecting water areas within the sea ice area and a combination strategy based on a principal component analysis for linking ocean model output with an altimetry-derived ocean topography are developed to enable a consistent computation of ocean surface currents., Mit Hilfe von Satellitenaltimetrie abgeleiteten geostrophischen Strömungen können Oberflächen-Meeresströmungen in polaren Regionen beobachtet werden. Jedoch zeichnen sich diese durch eine unregelmäßige und lückenhafte Datenverteilung aus. Neuartige Verfahren zur Detektion von Wasserflächen innerhalb des Meereises und zur Kombination der beobachteten dynamischen Ozeantopographie mit einem Ozeanmodell unter Verwendung einer Hauptkomponentenanalyse, erlauben eine konsistente Berechnung von Oberflächen-Meeresströmungen.

The coastal marine gravity field is not well modelled due to poor data coverage. Recent satellite altimeters provide reliable altimetry observations near the coast, filling the gaps between the open ocean and land. We show the potential of recent satellite altimetry for the coastal marine gravity modelling using the least squares collocation technique. Gravity prediction error near the coast is better than 4 mGal. The modelled gravity anomalies are validated with sparse shipborne gravimetric measurements. We obtained 4.86 mGal precision when using the altimetry data with the best coastal coverage and retracked with narrow primary peak retracker. The predicted gravity field is an enhancement to EGM2008 over the coastal regions. The potential improvement in alti- metric marine gravity will be beneficial for the next generation of EGM development.

Sea level change is an important indicator of climate change. Our study focuses on the sea level budget assessment of the Arctic Ocean using: (1) the newly reprocessed satellite altimeter data with major changes in the processing techniques; (2) ocean mass change data derived from GRACE satellite gravimetry; (3) and steric height estimated from gridded hydrographic data for the GRACE/Argo time period (2003–2016). The Beaufort Gyre (BG) and the Nordic Seas (NS) regions exhibit the largest positive trend in sea level during the study period. Halosteric sea level change is found to dominate the area averaged sea level trend of BG, while the trend in NS is found to be influenced by halosteric and ocean mass change effects. Temporal variability of sea level in these two regions reveals a significant shift in the trend pattern centered around 2009–2011. Analysis suggests that this shift can be explained by a change in large-scale atmospheric circulation patterns over the Arctic. The sea level budget assessment of the Arctic found a residual trend of more than 1.0 mm/yr. This nonclosure of the sea level budget is further attributed to the limitations of the three above mentioned datasets in the Arctic region.

Background: Few qualitative studies have focused on clinicians’ perspectives regarding treatment of suicidal people. Despite limited evidence and imperfect risk-assessment tools, the psychosocial therapy at the Danish suicide prevention clinics has been linked to reductions in numbers of repeated self-harm, deaths by suicide, and other causes. This merits an investigation into how clinicians describe their practice. Methods: Using a qualitative design, 10 semi-structured interviews were conducted and analyzed to describe the psychosocial therapy. Results: The practices that the therapists described could be categorized along four dichotomous continuums. These illustrated dilemmas encountered during treatment of suicidal patients: 1) intuitive vs. specific risk assessment, 2) meaningful vs. formal, 3) patient-oriented vs. therapist-oriented and 4) direct vs. indirect approach to suicide prevention. Conclusions: Treatment in the Danish Suicide Prevention Clinics is characterized by methodological flexibility and diversity and with an emphasis on a patient-oriented approach. Furthermore, clinicians balance knowledge available by switching between a direct and an indirect approach according to the perceived suicide risk. If suicide risk was perceived as high, they would administer a direct approach and if low, an indirect approach. Finally, there seems to be differences as to how effective therapeutic methodologies work in the practice of suicide prevention.

High-resolution satellite images of ocean color and sea surface temperature reveal an abundance of ocean fronts, vortices and filaments at scales below 10 km but measurements of ocean surface dynamics at these scales are rare. There is increasing recognition of the role played by small scale ocean processes in ocean-atmosphere coupling, upper-ocean mixing and ocean vertical transports, with advanced numerical models and in situ observations highlighting fundamental changes in dynamics when scales reach 1 km. Numerous scientific publications highlight the global impact of small oceanic scales on marine ecosystems, operational forecasts and long-term climate projections through strong ageostrophic circulations, large vertical ocean velocities and mixed layer re-stratification. Small-scale processes particularly dominate in coastal, shelf and polar seas where they mediate important exchanges between land, ocean, atmosphere and the cryosphere, e.g., freshwater, pollutants. As numerical models continue to evolve toward finer spatial resolution and increasingly complex coupled atmosphere-wave-ice-ocean systems, modern observing capability lags behind, unable to deliver the high-resolution synoptic measurements of total currents, wind vectors and waves needed to advance understanding, develop better parameterizations and improve model validations, forecasts and projections. SEASTAR is a satellite mission concept that proposes to directly address this critical observational gap with synoptic two-dimensional imaging of total ocean surface current vectors and wind vectors at 1 km resolution and coincident directional wave spectra. Based on major recent advances in squinted along-track Synthetic Aperture Radar interferometry, SEASTAR is an innovative, mature concept with unique demonstrated capabilities, seeking to proceed toward spaceborne implementation within Europe and beyond.

High-resolution satellite images of ocean color and sea surface temperature reveal an abundance of ocean fronts, vortices and filaments at scales below 10 km but measurements of ocean surface dynamics at these scales are rare. There is increasing recognition of the role played by small scale ocean processes in ocean-atmosphere coupling, upper-ocean mixing and ocean vertical transports, with advanced numerical models and in situ observations highlighting fundamental changes in dynamics when scales reach 1 km. Numerous scientific publications highlight the global impact of small oceanic scales on marine ecosystems, operational forecasts and long-term climate projections through strong ageostrophic circulations, large vertical ocean velocities and mixed layer re-stratification. Small-scale processes particularly dominate in coastal, shelf and polar seas where they mediate important exchanges between land, ocean, atmosphere and the cryosphere, e.g., freshwater, pollutants. As numerical models continue to evolve toward finer spatial resolution and increasingly complex coupled atmosphere-wave-ice-ocean systems, modern observing capability lags behind, unable to deliver the high-resolution synoptic measurements of total currents, wind vectors and waves needed to advance understanding, develop better parameterizations and improve model validations, forecasts and projections. SEASTAR is a satellite mission concept that proposes to directly address this critical observational gap with synoptic two-dimensional imaging of total ocean surface current vectors and wind vectors at 1 km resolution and coincident directional wave spectra. Based on major recent advances in squinted along-track Synthetic Aperture Radar interferometry, SEASTAR is an innovative, mature concept with unique demonstrated capabilities, seeking to proceed toward spaceborne implementation within Europe and beyond

Data fusion with multiple heterogeneous sensors has shown great importance for motion control and navigation filter design of autonomous vehicles. However, data fusion often requires the prior knowledge of the extrinsic transformations between sensors. This paper focuses on the usage of manifold optimization to calibrate the extrinsic transformation for a pair of sensors from a batch of measurements. Instead of reparameterization the transformation matrix in other forms, we formulate an objective function directly with the special Euclidean group. Then this manifold optimization problem is solved iteratively in a Gauss-Newton fashion. The usage of manifold optimization guarantees the obtained result being strictly within the special Euclidean group without the need of further operations like normalization and orthogonalization. The experimental results on both synthetic and real data show the superiority and robustness of the proposed method. Considering the performance and time consumption, the proposed approach is a good option for real applications.

2D sea level trend and variability fields of the Baltic Sea were reconstructed based on statistical modeling of monthly tide gauge observations, and model reanalysis as a reference. The reconstruction included both absolute and relative sea level (RSL) in 11 km resolution over the period 1900–2014. The reconstructed monthly sea level had an average correlation of 96% and root mean square error of 3.8 cm with 56 tide gauges independent of the statistical model. The statistical reconstruction of sea level was based on multiple linear regression and took land deformation information into account. An assessment of the quality of an open ocean altimetry product (ESA Sea Level CCI ECV, hereafter “the CCI”) in this regional sea was performed by validating the variability against the reconstruction as an independent source of sea level information. The validation allowed us to determine how close to the coast the CCI can be considered reliable. The CCI matched reconstructed sea level variability with correlation above 90% and root-mean-square (RMS) difference below 6 cm in the southern and open part of the Baltic Proper. However, areas with seasonal sea ice and areas of high natural variability need special treatment. The reconstructed RSL change, which is important for coastal communities, was found to be dominated by isostatic land movements. This pattern was confirmed by independent observations and the values were provided along the entire coastline of the Baltic Sea. The area averaged absolute sea level change for the Baltic Sea was 1.3 ± 0.3 mm/yr for the 20th century, which was slightly below the global mean for the same period. Considering the relative shortness of the satellite era, natural variability made trend estimation sensitive to the selected data period, but the linear trends derived from the reconstruction (3.4 ± 0.7 mm/yr for 1993–2014) fitted with those of the CCI (4.0 ± 1.4 mm/yr for 1993–2015) and with global mean estimates within the limits of uncerta

There is a growing need for geodetic reference frames that on a national level support the increasing use of global positioning services. Today, the vast majority of countries have their own national reference frame. In Europe this frame is normally aligned to ETRS89. This system is co-moving with the Eurasian tectonic plate. Global Navigation Satellite Systems (GNSS) and global positioning services are normally aligned to the Earth as a whole through a global reference frame like ITRF2014. Consequently, global positioning services does not give direct access to the national reference frame without a time-dependent transformation. A solution is to align the national reference frame directly to a global reference frame. In such a frame, the coordinates of a point fixed to the ground will change with time, - a fact leading to the expression dynamic reference frame (DRF).To be prepared for future challenges, the Nordic Geodetic Commission (NKG) initiated a pilot-project on DRF in Iceland. Iceland has a very active and complex geodynamic situation. It is located at the boundary of two tectonic plates and affected by seismic and volcanic activity, recent ice loading changes as well as glacial isostatic adjustment (GIA). Due to this, the traditional concept of a static geodetic reference frame is difficult to maintain at the uncertainty level required by modern applications. Iceland was therefore a natural place to investigate the concept of DRF. This paper focuses on the outcome and conclusions of the DRF project in Iceland. We give ten preconditions for a DRF. Living on an ever-changing Earth, we see that many of these precondition shave to be in place regardless of type of reference frame. Through the work in the Nordic countries and NKG, the Nordic area will be well prepared for the future challenges. However, some legal issues for instance, can be challenging. A two-frame solution combining static- and dynamic- reference frames seems like the best alternative in the

Trajectory generation is one of the most popular techniques for multi-rotors to achieve autonomous navigation capabilities. In this paper, we present an optimization-based approach for generating smooth, feasible and collision-free trajectories. Our method does not require a prior proper time allocation but attempts to optimize time allocation automatically. This method first optimizes trajectories subjected to dynamic constraints and 3D corridor constraints using a quadratic program. Then time allocation is optimized as a semidefinite program by leveraging semidefinite relaxation. A feasible solution is obtained using the rank-one approximation and used to update previous time allocation. This method run iteratively until a feasible trajectory is obtained. Our approach is validated with simulation results. Experimental results show the proposed method ensures to generate feasible trajectories in clutter environments.

In this thesis, methods are developed both to estimate water levels from satellite altimetry over rivers and to link these water levels from different satellite missions along the river. Thus, previously unobserved small rivers can be measured with high accuracy. The combination of the data significantly improves the spatial and temporal resolution of the river observation and allows observing inter-annual changes of flood events. The methods are tested and validated in the Mekong River Basin., In dieser Arbeit werden Methoden entwickelt sowohl um Wasserstände aus Satellitenaltimetrie über Flüssen abzuleiten als auch um diese Wasserstände von verschiedenen Satellitenmissionen entlang des Flusses zu verknüpfen. Damit können bisher unbeobachtete kleine Flüsse mit hoher Genauigkeit vermessen werden. Die Kombination der Daten verbessert die räumliche und zeitliche Auflösung der Flussbeobachtung signifikant und erlaubt es zwischenjährliche Schwankungen von Flutereignissen zu beobachten. Die Methoden werden getestet und validiert im Mekong Einzugsgebiet.

The ocean mean dynamic topography (MDT) is the surface representation of the ocean circulation. The MDT may be determined by the ocean approach, which involves temporal averaging of numerical ocean circulation model information, or by the geodetic approach, wherein the MDT is derived using the ellipsoidal height of the mean sea surface (MSS), or mean sea level (MSL) minus the geoid as the geoid. The ellipsoidal height of the MSS might be estimated either by satellite or coastal tide gauges by connecting the tide gauge datum to the Earth-centred reference frame. In this article we present a novel approach to improve the coastal MDT, where the solution is based on both satellite altimetry and tide gauge data using new set of 302 tide gauges with ellipsoidal heights through the SONEL network. The approach was evaluated for the Northeast Atlantic coast where a dense network of GNSS-surveyed tide gauges is available. The typical misfit between tide gauge and satellite or oceanographic MDT was found to be around 9 cm. This misfit was found to be mainly due to small scale geoid errors. Similarly, we found, that a single tide gauge places only weak constraints on the coastal dynamic topography.