MCGS

Development of a Multipurpose Cooperative GNSS Server

Aims

• Development of an innovative Multipurpose Cooperative GNSS Server (MCGS) which should:
  • Increase positioning accuracy for mass-market receivers using benefits of cooperative data processing.
  • Provide near-real-time service
  • Propose best positioning quality / cost ratio with high level of flexibility
• Perform study on ionospheric and tropospheric error mitigation strategies applicable in MCGS

Brief Description

Today, Global Navigation Satellite Systems (GNSS) are playing a notable role in numerous fields of our daily lives, ranging from leisure, sports and automotive to transport and precise surveying applications, to name but a few. A vast range of GNSS receivers are being utilized. These include cheap mass-market devices (e.g., within smartphones or trackers) as well as high-end multi-frequency receivers as they are used within professional industrial applications.

For many fields, the positioning accuracy of a single GNSS receiver is not sufficient. Consequently, differential or relative GNSS techniques have been developed. Even though these approaches allow the highest accuracy, the costs are tremendous. In the course of this project, a Multipurpose Cooperative GNSS Server (MCGS) is developed. The idea is to increase the positioning accuracy of all GNSS users within a specified region by organising them by means of a cooperative network. For this, all GNSS receivers transmit their raw observation or coordinates (in case of very low-cost receivers) data to a central processing facility. Thereafter, sophisticated data management and GNSS solver algorithms at the server side are used to compute the position of every single receiver. This is conducted in near-real-time and only the final position is returned to the user. By this strategy, the positioning accuracy of all connected users is increased, as differential or relative GNSS techniques can be applied that would have not been possible for stand-alone receivers.

Depending on the number of connected users and the observations they transmit (e.g., code pseudoranges, phase measurements etc.), Precise Point Positioning (PPP), Differential GNSS (DGNSS) or even Real Time Kinematic (RTK) techniques can be conducted. For single mass-market GNSS chips providing only the final position, these approaches cannot be implemented. Nevertheless, the MCGS offers a position correction mode for these receivers. This is achieved by reconstructing the standard point positioning algorithms of mass market receivers at the server side by using precise data (e.g., satellite ephemeris, ionospheric models) from external sources instead of broadcast data. In case one or more multi-frequency receivers are connected to the server, atmospheric characteristics can be derived. Within the project, a feasibility study on local atmospheric models and their implementation within the MCGS is conducted.

The result of the project is a demonstrator of the MCGS capable of handling multiple users within multiple user pools. State-of-the-art data transfer and management strategies capable of handling input from a large number of users are implemented. The multi-user functionality follows the concept of modern internet phenomena, such as e.g., social networks, peer-to-peer communication and cloud computing with the objective to bring benefits to all connected users by a cooperative effort. Besides an increased positioning accuracy for all users, MCGS is intended to be a low-cost solution for both users and providers. By enabling differential or relative GNSS techniques utilizing multiple receivers, expenses for equipment and maintenance of reference stations and user charges for reference providers can be saved. Beside the technical developments and tests, a business analysis and a roadmap to a later product/service are established.