Development of a Mobile Public Precise Positioning Service Based on the National GNSS Network (P3-Service)
The goal of this project is to develop a public mobile precise positioning service for consumer-grade receivers. Affordable consumer devices can currently provide positioning accuracy of 5-10 meters. Utilizing the GNSS data provided by FinnRef and its error models, the location accuracy is improved to 2 meters. However, for i.e. intelligent transport system positioning, two meters is typically not accurate enough. In this project, we develop new algorithms that can provide 0.5 meter accuracy, which is already sufficient for e.g. lane detection. These new algorithms will utilize the openly available FinnRef data as well as carrier phase measurements of consumer devices that are typically only used in professional surveying-grade devices. The algorithms are to be developed for smartphone platforms. The outcomes of the project will offer the Finnish industry and society a unique consumer-level precise point positioning service providing ten times higher accuracy than currently possible.
The national FinnRef network of permanent GNSS stations maintained by FGI is being renewed in 2012-2013. The measurements provided by FinnRef can be used for precise positioning due to the error modelling of satellite clocks, orbits as well as atmospheric errors
. In 2014, the measurement information provided by FinnRef was opened for whole Finland. There will be significant savings especially for professional users due to the free access to FinnRef information, but there is a great potential to utilize the network data for more accurate consumer-level positioning.
The objective of this project is to carry out research in developing a mobile public precise positioning service (P3-Serivce) based on the national GNSS network – FinnRef. Unlike the existing services that are targeted for high-end receivers for professional applications, the new service studied in the project will be targeted for low-cost receivers for the general public and consumers. A novel positioning algorithm will be developed to achieve a half-meter positioning accuracy using carrier phase measurements, which is ten times higher than that of the current positioning solution in smartphones. The positioning solution will take advantage of Cloud computing technology and utilize the assistance from the FinnRef network that consists of 20 reference stations around Finland. Each reference station includes a state-of-the-art high-end GNSS receiver and a modern broadband connection to the Internet.
The new positioning algorithm called Dual Core PPP-RTK (Precise Point Positioning-Real Time Kinematic) takes the advantages of both the current RTK and PPP technologies to overcome the disadvantages of either of these technologies. The developed method is expected to be a high performing positioning solution providing a half-meter positioning accuracy for all the roads and costal lines in Finland where an open view to the sky is available. The solution will be different from the current VRS (Virtual Reference Station) technology, which is targeted for high-end/geodetic-class receivers. Our solution is targeted to be a mass-market solution in car navigators and smartphones. The Dual-Core PPP-RTK algorithm will support a multi-constellation solution when GLONASS carrier measurements are also available and likewise when Galileo and BeiDou will be operational.
The solution to be developed in the project will be an enabling technology for the next generation ITS applications, e.g. lane-level and road safety applications; for new LBS applications in e.g. excavation work, mining and train yards and junctions, and for demanding maritime navigation in challenging environments, such as busy harbors and passages.
Project High Level Architecture
By utilizing the national GNSS network – FinnRef – this project will develop a high precise positioning service for low-cost GNSS receivers to meet the needs of new location-based applications. The service prototype will be implemented with a smartphone that outputs GNSS carrier-phase measurements by a low cost GNSS receiver. The smartphone partner in the project consortium will provide an interface to reach also the carrier-phase measurements of the low-cost GNSS receiver of a smartphone.
A new positioning algorithm, dual-core PPP-RTK, will be investigated in the project. It is a synthesis of the state-of-the-art high precise positioning technologies, such as PPP and RTK. Figure 1 shows the high-level system architecture of the whole solution from the technical aspect.
Figure 1: The high level architecture of the P3-Service
First, the FinnRef network is used as a wide-area augmentation network, and its observation data and associated products, e.g. precise orbits and clock data provided, are processed to generate corrections of GNSS errors. In the proposed PPP-RTK solution, GNSS errors are represented with the state space representation (SSR) approach, and the parameters of SSR are estimated with measurements and associated products related to the stations of the FinnRef network. These SSR parameters are disseminated to the client platform for precise positioning with a single frequency low-cost receiver. With the assistance of the SSR parameters, the client positioning algorithm performs the RTK solution to initialize and recover the PPP solution within a shorter convergence duration, and the PPP solution then performs as long as possible. The key points to be developed include the state space representation of GNSS errors and the smoothing PPP-RTK solution.
The whole solution consists of two major components: a server data processing component for GNSS error models and representations, and a client positioning component with the dual-core PPP-RTK algorithm.
September 2013 – December 2015