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  • Alain Geiger
Alain Geiger

Alain Geiger
ETH Zurich | ETH Zürich · Department of Civil, Environmental and Geomatic Engineering

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161
Publications
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Publications

Publications (161)
Article
Full-text available
Global Navigation Satellite System (GNSS) radio occultation (RO) is a space-based remote sensing technique that measures the bending angle of GNSS signals as they traverse the Earth's atmosphere. Profiles of the microwave index of refraction can be calculated from the bending angles. High accuracy, long-term stability, and all-weather capability ma...
Article
Full-text available
This paper focuses on the retrieval of refractivity fields from GNSS measurements by means of least-squares collocation. Collocation adjustment estimates parameters that relate delays and refractivity without relying on a grid. It contains functional and stochastic models that define the characteristics of the retrieved refractivity fields. This wo...
Preprint
Full-text available
Global Navigation Satellite Systems (GNSS) radio occultation (RO) is a space-based remote sensing technique that measures the bending angle of GNSS signals as they traverse the Earth's atmosphere. Profiles of the microwave index of refraction can be calculated from the bending angles. High accuracy, long-term stability, and all-weather capability m...
Article
The tropospheric refraction along the signal path is the same for GNSS and radar interferometry. However, different observation geometries, spatio-temporal sampling, signal processing methods, as well as signal wavelengths yield rather complementary measurements. The origin of this research is the question whether tropospheric delays retrieved at G...
Article
Full-text available
Tropospheric water vapor is one of the most important trace gases of the Earth's climate system, and its temporal and spatial distribution is critical for the genesis of clouds and precipitation. Due to the pronounced dynamics of the atmosphere and the nonlinear relation of air temperature and saturated vapor pressure, it is highly variable, which...
Article
Signals used for Earth observation, when travelling through the atmosphere, are sensitive to refractivity; especially high spatio-temporal variations of water vapor are difficult to model and correct. Remaining unmodeled tropospheric delays deteriorate the positioning solution and therefore limit the accuracy of sensing and navigation applications....
Preprint
Full-text available
Tropospheric water vapor is among the most important trace gases of the Earth’s climate system and its temporal and spatial distribution is critical for the genesis of clouds and precipitation. Due to the pronounced dynamics of the atmosphere and the non-linear relation of air temperature and saturated vapor pressure, it is highly variable which ha...
Article
Full-text available
Currently, helicopter operations according to Instrument Flight Rules (IFR) consist of high-altitude trajectories where the probability of collision with terrain is assumed to be very low. In such high altitudes, the risk of icing has to be considered, additionally, the flight time is unnecessarily long. Therefore, this paper elaborates on an optim...
Article
The Global Navigation Satellite System Pseudo Interference Reflectometry (GNSS-PIR) is proposed for ground-based soil moisture remote sensing in this letter. It combines the signal received by the up-looking right-hand circularly polarized (RHCP) antenna with that received by the down-looking left-hand circularly polarized (LHCP) antenna to form an...
Article
Full-text available
High spatio‐temporal variability of atmospheric water vapor affects microwave signals of Global Navigation Satellite Systems (GNSS) and Interferometric Synthetic Aperture Radar (InSAR). A better knowledge of the distribution of water vapor improves both GNSS‐ and InSAR‐derived data products. In this work, we present a collocation framework to combi...
Article
This study presents a comparison of tropospheric parameters, namely zenith tropospheric delay and total refractivity calculated using meteorological measurements from a Meteodrone and Global Navigation Satellite Systems (GNSS) stations. A Meteodrone is a unique Unmanned Aerial Vehicle (UAV) originally designed for automatic measurements of meteorol...
Article
Full-text available
Nowadays, GNSS (Global Navigation Satellite System) receivers can measure with sampling rates up to 100 Hz, and it is possible to provide displacements at a level of precision of a few millimeters. This opened an interesting field of applications, e.g. for disciplines that monitor dynamic movements, like seismology or structural health monitoring....
Chapter
Over the last decade, near real-time analysis of GPS data has become a well-established atmospheric observing tool, primarily coordinated by the EIG EUMETNET GPS Water Vapour Programme (E-GVAP) in Europe. In the near future, four operational GNSS will be available for commercial and scientific applications with atmospheric science benefiting from n...
Chapter
In this section a summary of the national progress reports is given. GNSS4SWEC Management Committee (MC) members provided outline of the work conducted in their countries combining input from different partners involved. In the COST Action paticipated member from 32 COST countries, 1 Near Neighbour Country and 8 Intrantional Partners from Australia...
Article
Global navigation satellite system (GNSS) antennas buried underneath a snowpack have a high potential for in situ snow water equivalent (SWE) estimation. Automated and continuous SWE quantification independent of weather conditions could enhance snow hydrological monitoring and modeling. Accurate and reliable in situ data are needed for the calibra...
Presentation
Full-text available
Water vapor is the most variable parameter of the troposphere and accounts for most of the errors in the tropospheric modeling. The majority of water vapor is distributed below the height of 3 km and the assessment of the quality of tropospheric products in the lower troposphere still remains a challenge. Usually, the Global Navigation Satellite Sy...
Article
Full-text available
The PermaSense project is an ongoing interdisciplinary effort between geo-science and engineering disciplines and started in 2006 with the goals of realizing observations that previously have not been possible. Specifically, the aims are to obtain measurements in unprecedented quantity and quality based on technological advances. This paper describ...
Article
Full-text available
We compare tropospheric delays from Global Navigation Satellite Systems (GNSS) and Synthetic Aperture Radar (SAR) Interferometry (InSAR) in a challenging mountainous environment in the Swiss Alps, where strong spatial variations of the local tropospheric conditions are often observed. Tropospheric delays are usually considered to be an error for bo...
Presentation
Full-text available
Space-borne microwave techniques, such as the Global Navigation Satellite Systems (GNSS) or Synthetic Aperture Radar Interferometry (InSAR), are subjected to the atmospheric delay. The delays estimated by one technique can be useful for mutual corrections. The GNSS technique is characterized by very high temporal but sparse spatial resolution. In c...
Conference Paper
The GPS refractometry method is presented to derive snow water equivalent (SWE) by using refracted GPS L1 signals from a low-cost antenna buried underneath the snowpack. The GPS monitoring system is installed at 2536 m a.s.l. in the Swiss Alps. GPS refractometry is able to correct the influence of the snowpack above the buried antenna. The systemat...
Preprint
Full-text available
The PermaSense project is an ongoing interdisciplinary effort between geo-science and engineering disciplines started in 2006 with the goals to make observations possible that previously have not been possible. Specifically the aims are to obtain measurements data in unprecedented quantity and quality based on technological advances. This paper des...
Article
Full-text available
This paper deals with the detection of small movements of a GNSS (Global Navigation Satellite System) station by means of high precision estimates of the instantaneous station velocity. The aim is to detect hazardous displacements in real-time, in order to quickly provide movement information to facilitate a GNSS monitoring system. The station velo...
Article
Full-text available
By means of the time derivatives of Global Navigation Satellite System (GNSS) carrier-phase measurements, the instantaneous velocity of a stand-alone, single GNSS receiver can be estimated with a high precision of a few mm/s; it is feasible to even obtain the level of tenths of mm/s. Therefore, only data from the satellite navigation message are ne...
Presentation
Full-text available
In this study we evaluate the feasibility of using the tropospheric delays retrieved from Global Navigation Satellite Systems (GNSS) for the space-borne Synthetic Aperture Radar Interferometry (InSAR). The GNSS-based tropospheric models are interpolated for the points of 37 InSAR COSMO-SkyMed satellite acquisitions in a period that spans from 2008...
Article
Full-text available
Global Navigation Satellite Systems (GNSS) contribute to various Earth observation applications. The present study investigates the potential and limitations of the Global Positioning System (GPS) to estimate in situ water equivalents of the snow cover (snow water equivalent, SWE) by using buried GPS antennas. GPS-derived SWE is estimated over thre...
Article
Full-text available
The tropospheric delay of a microwave signal affects all space geodetic techniques. One possibility of modeling the delay is by introducing tropospheric models from external data sources. In this study, we present high-resolution models of tropospheric total refractivity and zenith total delay (ZTD) for the alpine area in Switzerland. The troposphe...
Article
Full-text available
Global Navigation Satellite Systems (GNSS) contribute to various Earth observation applications. The present study investigates the potential and limitations of the Global Positioning System (GPS) to estimate in situ water equivalents of the snow cover (snow water equivalent, SWE) by using buried GPS antennas. GPS derived SWE is estimated over thre...
Article
Full-text available
Observations from a submerged GNSS antenna underneath a snowpack need to be analyzed to investigate its potential for snowpack characterization. The magnitude of the main interaction processes involved in the GPS L1 signal propagation through different layers of snow, ice, or freshwater is examined theoretically in the present paper. For this purpo...
Article
Full-text available
GPS positioning is often assimilated to trilateration and even to triangulation methods. Both comparisons are wrong because GPS observations are pseudoranges containing clock errors. The geometric interpretations of GPS relative positioning and trilateration method are presented. Receiver clock parameter is also analyzed from a geometric point of v...
Article
Full-text available
We revisit the geometric interpretation of GPS dilution of precision (DOP) factors giving emphasis on the geometric impact of the receiver clock parameter on the conventional GPS positioning solution. The comparison is made between the solutions with and without an estimated receiver clock parameter, i.e., conventional GPS versus pure trilateration...
Article
Full-text available
Precise positioning requires an accurate a priori troposphere model to enhance the solution quality. Several empirical models are available, but they may not properly characterize the state of troposphere, especially in severe weather conditions. Another possible solution is to use regional troposphere models based on real-time or near-real time me...
Technical Report
Published by Department of Civil, Environmental and Geomatic Engineering
Presentation
In ionosphere stormy days, the ionospheric residuals on the single-difference level could reach a critical value even for short baselines in a Ground Based Augmentation System (GBAS) network. Wang et al. (2014) have analyzed the ionospheric residuals and spatial gradients in Switzerland using around 40 Automated GNSS Network for Switzerland (AGNES)...
Article
The developments in GNSS receiver and antenna technologies, especially the increased sampling rate up to 100 sps, open up the possibility to measure high-rate earth- quake ground motions with GNSS. In this paper we focus on the GPS errors in the frequency band above 1 Hz. The domi- nant error sources are mainly the carrier phase jitter caused by th...
Article
Full-text available
In 2014 the by far largest German lake has been newly surveyed. The transnational project is funded by the European Union and delivers a detailed 3D-model of the lakefloor. The German project name is »Tiefenschärfe – Hochauflösende Vermessung Bodensee «, which in English roughly means: high-resolution survey of Lake Constance. The German term »Tief...
Article
Summary Within the project “Tiefenschärfe – hochauflösende Vermessung Bodensee” a high-resolution seamless terrain model is created using airborne topobathymetric laserscanning and multibeam echosounder (MBES) techniques. The project visualizes the enormous wealth of features of underwater landscapes of lakes. The combination of hydroacoustic (mult...
Article
Full-text available
In sport science, Global Navigation Satellite Systems (GNSS) are frequently applied to capture athletes' position, velocity and acceleration. Application of GNSS includes a large range of different GNSS technologies and methods. To date no study has comprehensively compared the different GNSS methods applied. Therefore, the aim of the current study...
Article
The alignment challenge presented by the Compact Linear Collider (CLIC) project requires us to look closely at the ultra-high frequencies (< 1 km) of the gravity field and our ability to model or determine underground equipotential profiles at a very high level of precision. This is of particular importance in the context of an alignment system bas...
Chapter
A new system for measuring underground variations of the deflection of the vertical is presented. Based on geodetic and interferometric tilt measurements along a profile, it is designed to finally determine variations of equipotential profiles to better than 10 μm over 200 m with respect to a straight line. This condition comes from the pre-alignme...
Presentation
In current Global Navigation Satellite System (GNSS) differential single-frequency data processing, ionospheric delays are considered to be considerably reduced for short baselines in regional network. However, under strong ionosphere activities the remaining ionospheric effects on the single-difference level and their short-term variations may not...
Conference Paper
During approach and landing of airplanes, the Ground Based Augmentation System (GBAS) is used to augment the Global Positioning System (GPS) positioning by delivering differential corrections. The ionospheric delays are typically considered to be removed by generating differential observations if the baseline between the GBAS station and airplane i...
Conference Paper
The aim of this study is to develop a simplified analytic method to assess the performance of GNSS navigation and to analyze the impact of erroneous measurements. The method uses the mathematical description of continuous satellite distributions in order to simplify and generalize the equation for covariance and systematic error propagation. Its re...
Article
GPS rates based on data of an extended continuous and campaign-type GPS network in the North Aegean domain are presented. The data processed for the time period 1993–2009 is used to analyze the complex kinematic and deformation fields in the North Aegean Sea and adjacent regions. The presence of slowly deforming areas is investigated. Southern Bulg...
Poster
Full-text available
In this research project, the potential of GPS techniques for the observation of snow heights and snow water equivalent is investigated. For this purpose, permanent GPS stations were installed at the Weissfluhjoch test site of the Institute for Snow and Avalanche Research SLF in Davos, Switzerland. A feasibility study was carried out at the test si...
Article
Full-text available
Switzerland lies across one of the most complex plate boundary in the world. With a 100 Ma of deformation history, and a wide diversity of deformation mechanism, it is an ideal place to study the link(s) between small strain rates measured at the surface and stress dissipated at depth. The link is of genuine interest for seismic hazard assessment a...
Article
Within Switzerland, the deformation rates are small compared to tectonically more active regions in Europe. Velocities are derived from GNSS campaign data incorporating measurements from 1988 to the most recent campaign in 2010 (CHTRF2010). Their magnitudes are well below 1mm per year relative to the station in Zimmerwald located on the Swiss plate...
Poster
Full-text available
In this research project, the potential of GPS techniques for the observation of snow heights and snow water equivalent is investigated. For this purpose, permanent GPS stations were installed at the Weissfluhjoch test site of the Institute for Snow and Avalanche Research SLF in Davos, Switzerland. A feasibility study was carried out at the test si...
Article
Full-text available
Since winter 2010/2011, a network of permanent GPS stations is being set up in the Matter Valley (Swiss Alps). The aim is to monitor the time variable movement of potentially instable rock glaciers. The network has been established in the framework of the X-Sense project, currently totaling more than 20 stations. X-Sense is an interdisciplinary pro...
Thesis
Full-text available
In der vorliegenden Arbeit wird die Bestimmung von Schneehöhen und Schneemengen mit GPS-Messungen untersucht. Schneehöhen und Schneemengen sind in diversen Bereichen von Interesse. Dazu gehören der Wintersport, der Lawinenschutz, der Hochwasserschutz aber auch die Klimaforschung. Die Schneemenge ist räumlich sehr variabel und kann nur mit vielen Me...
Article
Full-text available
COupled seismogenic GEohazards in Alpine Regions (COGEAR) is an interdisciplinary natural hazard project investigating the hazard chain induced by earthquakes. It addresses tectonic processes and the related variability of seismicity in space and time, earthquake forecasting and short-term precursors, and strong ground motion as a result of source...
Conference Paper
This paper presents a new method to detect small and rapid movements in real-time with a single L1-GPS receiver. The method is based on the prediction of single differences between satellites by appropriate Filter methods. The movements' detection is based, on the one hand, on displacements computed with multiple prediction lengths, and on the othe...
Conference Paper
In a measurement campaign, a dense network of 34 GNSS (GPS+GLONASS) receivers was set up in an alpine region of Switzerland on an area of 10km × 10km. The investigation focused on the retrieval of water vapor information from GNSS receivers on small temporal and spatial scales. Radiosonde launches during the campaign provided the means to validate...
Poster
Full-text available
 Goal: Investigation of the potential of GPS techniques for the observation of snow heights and snow water equivalent (SWE).  5 GPS stations installed at the Weissfluhjoch test site of the Institute for Snow and Avalanche Research SLF near Davos, Switzerland (Fig. 1).  Use of low-cost GPS receivers and antennas.  First feasibility study carried...
Article
Water vapor is involved in many atmospheric processes and is therefore a crucial quantity in numerical weather prediction (NWP). Recent flood events in Switzerland have pointed out several deficiencies in planning and prediction methods used for flood risk mitigation. Investigations have shown that one of the limiting factors to forecast such event...
Article
In recent years GPS has become an important tool to measure not only the co-seismic and post-seismic displacements but also dynamic ground motions produced by large earthquakes. The latest generation of GPS receivers is capable of tracking at 100 Hz potentially capturing high-frequency signals and so could recover very broadband earthquake motions...
Article
Water vapor is a key variable in numerical weather prediction, as it plays an important role in atmospheric processes. Nonetheless, the distribution of water vapor in the atmosphere is observed with a coarse resolution in time and space compared to the resolution of numerical weather models. GPS water vapor tomography is one of the promising method...
Article
Full-text available
Three hydrostatic displacement monitoring system applications in Switzerland are discussed; the first concerns experience gained monitoring the foundation of the Albigna dam, the second relating to the underground stability of the Swiss Light Source synchrotron and the third concerning the deformation of a bridge near the city of Lucerne. Two diffe...
Article
Researchers at the Swiss Federal Institute of Technology in Zurich have developed the Atmospheric Water Vapor Tomography Software (AWATOS) for estimating humidity profiles. Water vapor plays an essential role in the dynamics and thermodynamics of the atmosphere, especially storm systems, on local, regional, and global scales. To assess the potentia...
Article
In 1997 swisstopo began to install and operate the Automated GPS Network for Switzerland (AGNES). Since then the network has been extended to more than 30 stations. From the time series swisstopo derives velocities which are used to create kinematic models of Switzerland under the assumption that the velocities correspond to the tectonic motion. Ho...
Article
Water vapor affects tropospheric dynamics, thermal feedback, and refractivity, thus forming a crucial parameter in meteorology, climatology, and geodesy. The accurate knowledge of the 3D tropospheric water vapor field is essential for initializing precise numerical weather predictions, especially for quantitative precipitation forecasting. In now-c...
Article
Water vapor plays an important role in atmospheric processes and is therefore a key quantity in numerical weather prediction (NWP). Nevertheless, the distribution of water vapor in the atmosphere is only measured with a coarse resolution in time and space. One of the promising methods to enhance the spatio-temporal resolution is GNSS water vapor to...
Article
The Eastern Mediterranean forms the seismically most active region of the Alpine-Mediterranean plate boundary. It is characterized by the collision between the Eurasian and African plates. The collision is closely related to continental subduction and formation of the pronounced Hellenic trench system. In addition to the relatively slow CCW rotatio...
Article
The Hellenic plate boundary region, located in the collision zone between the Nubian/Arabian and Eurasian lithospheric plates, is one of the seismo-tectonically most active areas of Europe. During the last 15 years, GPS measurements have been used to determine the crustal motion in the area of Greece with the aim to better understand the geodynamic...
Article
Greece is characterized by high seismotectonic activity. Extended Global Positioning System (GPS) reoccupation and continuous networks have been measured in order to study the crustal motion and deformation in this region, with particular interest in earthquake-related effects. In this article we present GPs-derived coseismic displacements in Greec...
Article
The calculation of recent crustal movements and the associated crustal deformation rely on a suitable interpolation of geodetic measurements with repetition cycles of years or decades and modern GPS permanent networks. A common interpolation methods is the least-square collocation (LSC). LSC requires some a priori assumptions about the characterist...
Article
Enhanced ground-based methods for precise sea surface height (SSH) measurements have been developed, in order to contribute to the improvement of sea level monitoring and provide local-scale information on the short-wave structure of the marine gravity field. These methods include airborne laser altimetry, seaborne ultrasound altimetry, seaborne mu...
Article
This paper presents a) recent developments in ground based GPS-tomography for the determination of atmospheric water vapor content b) the impact of GPS determined humidity profiles on to operational weather forecast and c) the influence of an additional satellite navigation system as Galileo on the quality of the tomographic solution. As the occurr...