Precise Point Positioning to support an automatic entering of a waterway lock

Kurzfassung

Inland waterway transport is the transport mode with the lowest CO2 emission per tonne kilometre. However, there is a substantial potential for modal shift from road and rail to inland vessel transport. The increase of the grade of automation or even autonomous inland vessels could be a key enabler for this modal shift. By far the most challenging phase of inland navigation is the passing of waterway locks. Here, typically a ship with the dimension of 11.4 x 100 m has to enter a 12 m wide lock chamber, leaving just a few dm space on each side of the vessel. In order to support the automation of this manoeuvre, very accurate position, heading, turn rate and velocity information is required. Within the project SCIPPPER (2018-2022) such a driver assistant function has been developed. The idea was using the absolute Precise Point Positioning (PPP) instead of Real Time Kinematic (RTK) to achieve the required 10 cm horizontal accuracy. The reason was an expected reduction in the amount of PPP correction data and a significantly enlarged service area. Both facts would enable the correction data transmission over the VHF Data Exchange System (VDES) - the next generation of the Automatic Identification System (AIS). While a stable mobile internet connection is unfortunately not available at all inland waterways, currently AIS Base stations are being operated on all main inland waterways in Germany. By upgrading the AIS base stations to VDES stations, in the future all inland vessels on the main waterways could potentially benefit from the highly accurate positioning service. Besides the high accuracy, the reduction of the convergence time is one of the key challenges for the application of PPP for inland vessels. In order to shorten the PPP convergence time, we were using an SSR (state space representation) correction service from a regional network including not only global corrections like satellite clock, orbit, code and phase biases but also regional ionospheric and tropospheric corrections. These corrections were provided by using the GNSS station network of SAPOS (Satelliten Positionierungsdienst der deutschen Landesvermessung). In cooperation with the Working Committee of the Surveying and Mapping Agencies of the States of the Federal Republic of Germany (AdV) and Geo++, an SSR correction data stream has been prepared and optimised for the inland vessel application. By separating the corrections into high (5s update) and low rate (30s update) corrections, an average data rate of about 0.3 kbits/s was achieved, which is a significant reduction compared to RTK correction (4-5 kbit/s). In the paper the details of our real time PPP positioning solver with ambiguity resolution based on GPS and GALILEO observations will be given. Furthermore, the results of static as well as dynamic measurement campaigns in challenging inland waterway scenarios will be presented. In the final demonstration of the SCIPPPER project an 82 m long vessel automatically entered a waterway lock by using PPP as the main source for global positioning of the vessel. While the paper focuses on the positioning part, also a main overview of the complete driver assistant function will be presented.