## 3 Use of GNSS Carrier Phase Observations in Various Fields of Science  
While considering carrier phase GNSS observations, one should also mention their practical applications. Next to geodetic and topographic surveys, the static method is widely used to calculate high accuracy three-dimensional coordinates in traverse stations for objects such as roads or railways, accurately determining the azimuth for establishing the network's orientation or setting points for monitoring deformations of objects. A mobile GNSS-based positioning system provides an excellent tool to quickly, accurately and reliably position points of details or features which may need to be precisely mapped. Detail surveys typically require an accuracy between 1 and 10 cm. There are also some applications, like utility mapping, which require decimeter accuracies. The usefulness of geodetic techniques, in particular GNSS technology, for monitoring different kinds of deformations is also a common practice. This is usually performed by setting a network of geodetic satellite receivers, obtaining accuracies in the order of sub-centimeters. The use of a low-cost u-blox GPS device may be an example, showing that good results for such applications can be achieved [28]. Other researchers presented wireless monitoring systems, consisting of GNSS receivers and accelerometers, for long-term monitoring installations, landslide monitoring or efficient and effective reconstruction of the railway and tram tracks' geometry [29; 30; 31; 32]. In the case of constructions of super-high buildings, satellite-based techniques may be very important to help control them vertically and also analyze their horizontal motions [33]. More recent research demonstrates the advantage of the integration of mass-market smartphone GNSS signals with other precise sensors for geoscience applications, where accelerometers and gyroscopes are additionally used for earthquake detection or ionospheric/tropospheric disturbances [34; 35]. GNSS technology also puts forward the foundations for atmospheric precipitable water vapor analysis. Compared to the conventional methods of atmospheric water vapor detection (such as radio sounding, microwave radiometer, satellite remote sensing, etc. ), GNSS-based atmospheric water vapor detection has high precision and high space-time resolution and became a powerful tool which is widely used nowadays. Since the water vapor may be easily derived from inverting tropospheric delays, which is estimated in GNSS post-processing, the outcomes may be incorporated into the analysis of the rainfall process to support the weather forecast [36; 37]. Additionally, scientists have been trying to provide novel methods to measure the impact of ionosphere on GNSS measurements. Despite being one of the major sources of error affecting high-accuracy GNSS applications, ionospheric scintillations are an important tool to study the behavior of this layer of the atmosphere [38]. Finally, low-cost GNSS receivers have been widely used for precise navigation purposes. Delivering raw dual frequency data, receivers allow us a more sophisticated processing, such as the double-difference approach, and therefore, a more accurate positioning. However, high accuracies can be generally obtained only with an open sky visibility, without any obstructions. The problem appears while positioning in urban environments or being indoors, even using low-cost GNSS receivers equipped with highly sensitive antennas. In such situations, satellite receivers should be integrated with additional vision or microelectromechanical (MEMS) sensors [39; 40]. With the development of global satellite navigation systems, kinematic Precise Point Positioning (PPP) is one of the recent techniques to make positioning efficient and cost effective by reducing equipment costs for surveying purposes. It does not require any additional data from a reference station and can provide a solution with a centimeter to decimeter level of position accuracy both in static and kinematic modes [41; 42].