Precise GNSS based positioning for automated inland vessel navigation

Kurzfassung

Inland navigation and shipping is an important pillar of the European Transport System. To support the skipper, advanced driver assistant functions need to be developed. The project SCIPPPER (2018-2021) aims the development of an assistance system used for automatically entering/exiting a lock within. For such a system all propulsion and steering devices of the vessel have to be controlled simultaneously including rudder, engine and thrusters. This requires very accurate and reliable information about, position, velocity and orientation of the vessel. For this purpose the combined usage of absolute positioning using Global Navigation Satellite Systems (GNSS) and relative positioning using near field sensors is planned. In order to achieve the required accuracies, Precise Point Positioning (PPP) techniques will be applied. This project is planned to be a pilot project for the usage of SSR (State Space Representation) corrections provided by SAPOS (Satelliten¬position-ierungsdienst der deutschen Landesvermessung) reference station network. In order to support the development of the different technologies within the project, already several field trials have been performed, where GNSS positioning is tested using State Space Representation (SSR) correction data. In comparison to RTK, so called observation state representation (OSR) corrections, SSR corrections could be used in a larger region and have the potential for a significant reduction in the required data rate. For the SSR corrections all individual error sources of the GNSS system like: orbit, satellite clocks, code + phase biases, troposphere and ionosphere errors need to be determined by a reference station network. One of the advantages of the SSR approach is that the corrections for the different error components can be sent with different update rates. Fast varying error components like clocks will be sent with a higher update rate than slower varying error components like satellite orbits. The main drawback of using SSR corrections for positioning is that the RTK approach of applying double differences with the measurements of the reference station can’t be used anymore, but a PPP has to be applied. Due to the lack of standardized SSR messages, currently only proprietary solutions for PPP services and positioning software exist. That means that a commercial PPP service can only be used in combination with a special receiver provided by the service provider. In cooperation with the Working Committee of the Surveying and Mapping Agencies of the States of the Federal Republic of Germany (AdV) and Geo++ within the SCIPPPER project first measurement campaigns for the application of SSR correction on an inland vessel were performed on the Danube River in the vicinity of Regensburg. The AdV was providing a SSR test data stream, calculated from a GNSS reference station network in Bavaria. The company GEO++ provided a SSR2OSR software (http://www.geopp.de/gnsmart/) for the onboard calculation of a virtual reference station (VRS) based on SSR correction data. The software finally provides OSR corrections in standard RTCM3 format, which could be used by any RTK capable receiver to calculate a precise position solution. This paper will give an overview of the results of the first measurement campaigns using SSR corrections onboard an inland vessel.