Geodetic use of GPS
Global Navigation Satellite System (GNSS) is the generic term for realised or planned systems for satellite-based positioning. There are currently four global navigation satellite systems: the US American GPS, the Russian GLONASS, the European Galileo and the Chinese BeiDou. Additional regional and complementary systems such as WAAS and EGNOS are being developed to support GNSS in terms of availability, integrity and reliability.
All modern GNSS are passive systems. The essential components are centralized and cannot be influenced by the user. The GNSS user receives satellite signals and can calculate his position, velocity and time. Although GNSS was developed for navigation applications (absolute positioning) with an accuracy in the metre range, it forms more than one measurement system and can be used for high-precision surveying tasks. For this purpose, all occurring error influences, such as tropospheric and ionospheric propagation delays, satellite orbit errors and multipath effects, have to be handled by measurement, evaluation methods, models or the use of reference data. In addition, the use of phase observations for these applications, cm-accurate positioning, is indispensable.
GNSS offers innumerable applications for the most diverse areas of life. In addition to navigation applications in shipping, cars or aircraft, GNSS can be used for geodetic tasks. For example real estate surveying, engineering surveying (tunnel network, dam control) or in geodynamics (observation of plate movements or crustal deformation by permanent measurements, observation of seismic movements caused by earthquakes) or monitoring of the atmosphere (troposphere and ionosphere). At GIK, two main topics concerning GNSS applications are important: Monitoring of the troposphere including water vapour content and determination of crustal deformation, especially in the Upper Rhine Graben area.
Further Fields of Research
- Transformation of GPS heights into official heights
- Comparative study of commercial GPS Analysis Software
- Time series analysis of GPS observations
- Developing a tiered approach for the processing of three-dimensional GPS results, taking into account the need for accuracy and reliability
- Investigation of problems with the transformation of GPS results using national reference systems (strict / approximated ellipsoid transformation)
- Development of models for the combination of GPS heights with official heights; conversion of GPS heights into official height systems
- Analysis of the accuracy and reliability of RTK-GPS measurements
- Use of GPS for high precision engineering surveys
- Development of Sonar Underwater Navigation System (SUNS) in the Alpbach Summer School "LI Application and Science for Systems Navigation Satellite"