Global Navigation Satellite System is a spatial data acquisition technique, mostly used in navigation and positioning. One of the main components of this technique is the satellite visibility, which refers to the connection between the satellite and the ground receiver. It is known that the GNSS positioning systems are not as performing in urban areas due to the dense coverage of obstacles (buildings, trees, high terrain etc.). These obstacles can obstruct and reflect the lines of sight between the satellite and the ground receiver which can affect the quality of the performance of the GNSS service. The geometry configuration of the satellites above the receiver is another important aspect that has to be taken into consideration.

This research focuses on implementing a simulation similar to that of GNSS mission planning tools, but using point cloud data as the 3D representation of the surroundings of the receiver and using only the GPS constellation of satellites. Due to the large size of a point cloud sample, two visibility algorithms have been implemented to filter the necessary 3D data. The main output of the simulation are the dilution of precision values which give further information about the satellites' positions. The main purpose of this research is to understand the dilution of precision values, which are directly related to the geometry of the satellite configuration above the receiver. Understanding the behaviour and how the receiver's environment influences the DoP values can result in leading GNSS surveying missions with better results.

This output is then compared with the data acquired from a GNSS receiver in a real scenario. While the results are not favorable for the implemented simulation, it gives a better understanding of the surroundings of the receiver's location by using point cloud data than the already existing online GNSS tools.

The NMCAs (National Mapping and Cadastral Agencies) of European countries have different cadastral survey accuracy standards (European Global Navigation Satellite Systems Agency, 2019). In order to meet these standards, the appropriate equipment and services should be determined. The augmentation service Galileo High Accuracy Service (HAS), that is planned for 2022, will provide high accuracy Precise Point Positioning (PPP) corrections. Unlike other high-accuracy services, the Galileo HAS will be free of charge and available worldwide, without the need to be close to a base station or to a dedicated provider network. The PPP corrections will be provided through the Galileo signal as well as through the Internet (EUSPA, 2021). Because of the potential of the Galileo HAS, for the Synthesis Project we want to get insight in the accuracy of the augmentation service. Since a big share of cadastral surveys is performed in the built environment, we also want to determine the accuracy in an urban canyon. With the found accuracy, we can possibly judge whether Galileo HAS is suitable for cadastral surveys in the Netherlands, by comparing the measured accuracy to cadastral survey accuracy standards of the Dutch Kadaster.
As a final conclusion for this project, Galileo HAS is still a technique under development and the PPP-based correction methods are currently not as accurate as the RTK-based ones. Galileo HAS will present in the future ways to correct these errors.