Availability of the GNSS Geodetic Networks Position during the Hydrographic Surveys in the Ports

Geodetic network GNSS receivers are more commonly associated with positioning systems used in maritime hydrography. In terms of positioning accuracy when no terrain obstacles are present, they meet international hydrographic surveys standards (S-44) fully. Those standards are defined as 1m (0.95) for Exclusive Order and 2m (0.95) for Special Order. It is equally as important to ensure access to position which error is not higher than above mentioned maximum values. This is most often determined by the density of port infrastructure. This article presents the results of analysis of availability of hydrographic system that operates based on geodetic GNSS networks. Hydrographic surveys in question were undertaken in inner basins with diverse infrastructure. Three representative types of ports were selected for this reason: fishing type (Hel), medium sized, modern commercial type (Gdynia) and highly congested, narrow canal type (Gdansk – Motlawa). A non-public, geodetic GNSS network was used for all surveys. It is worth mentioning that the above network is at the moment the only available network that provides both GPS and GLONASS corrections. The surveys provided evidence that geodetic GNSS networks can be successfully utilised to determine position of hydrographic vessel in low and moderately developed ports as well as in Exclusive and Special Orders. In highly congested ports however, the availability of the above mentioned method of measurement can be insufficient to realise a survey

Analysis of the possibilities in railways shape assessing using GNSS mobile measurements

In recent years, a dynamic development of satellite positioning techniques using both static and mobile GNSS coordinates register mode can be observed. In addition, still developing Real-time GNSS Networks, post-processing algorithms and another measurement signal analysis algorithms, make the satellite measurements increasingly used in railway industry sector. In the article the possibilities which follows from the mobile satellite measurements in railway engineering are briefly presented. In the years 2009-2015, the authors conducted a series of field investigations on operated railway lines. The obtained results of these measurements led to the development of a number of algorithms that increase the range of applicability of GNSS measurements. The analysis of obtained results also showed how the accuracy of the measurements have increased since 2009. The achieved accuracy has been increased due to a development of GNSS positioning systems as well as improvement of the measurement methodology, i.e. configurations of satellite receivers and layouts of their placement on a mobile measuring platform. It was also found that the development of data analysis algorithms contributed to the increase in the obtained accuracy in assessment of a railway track axis shape. The authors indicate the possibilities of applying GNSS techniques at various stages of construction and operation of railways. According to the authors, the most important advantage of both the presented measurement technique and computational methodology is the ability to effectively and relatively low-cost data acquisition regarding the existing state of the railway line. These data can be successfully used to design changes to the geometry of railway lines, and therefore satellite positioning has enormous application potential in the process of modernization of operated railway lines

Evaluation of Positioning Functionality in ASG EUPOS for Hydrography and Off-Shore Navigation

The paper discusses the ASG EUPOS services. There is presented an assessment of the possibility of using this system selected sites in hydrography and off-shore navigation tasks. Presented and analyzed the experiments were carried out in the port of Gdynia and on the Gulf of Gda?sk. The results obtaining in the work confirm the possibility of the position accuracy guaranteed by ASG EUPOS services. The obtained accuracy greatly exceeds the needs and requirements of coastal navigation and underwater mining and exploration of sea bottom

Application of Least Squares with Conditional Equations Method for Railway Track Inventory Using GNSS Observations

Satellite geodetic networks are commonly used in surveying tasks, but they can also be used in mobile surveys. Mobile satellite surveys can be used for trackage inventory, diagnostics and design. The combination of modern technological solutions with the adaptation of research methods known in other fields of science offers an opportunity to acquire highly accurate solutions for railway track inventory. This article presents the effects of work carried out using a mobile surveying platform on which Global Navigation Satellite System (GNSS) receivers were mounted. The satellite observations (surveys) obtained were aligned using one of the methods known from classical land surveying. The records obtained during the surveying campaign on a 246th km railway track section were subjected to alignment. This article provides a description of the surveying campaign necessary to obtain measurement data and a theoretical description of the method employed to align observation results as well as their visualisation. Document type: Articl

Maritime DGPS System Positioning Accuracy as a Function of the HDOP in the Context of Hydrographic Survey Performance

The Differential Global Positioning System (DGPS) is a marine navigation system operating at frequencies of 283.5–325 kHz, which is now the primary method for locating vessels in coastal shipping, as well as hydrography and mapping systems worldwide. Its positioning accuracy is determined by the following: the pseudorange error to Global Positioning System (GPS) satellites, the age of pseudorange corrections, and the value of the Horizontal Dilution of Precision (HDOP), which, in terms of accuracy, is crucial in positioning using GPS satellites. In 2020, the International Hydrographic Organization (IHO) introduced a new (the highest) order of hydrographic surveys, i.e., the Exclusive Order, which requires a positioning system to provide an accuracy of 1 m (p = 0.95). The aim of this article is to provide an answer to the question as to whether the maritime DGPS system, whose positioning accuracy is constantly increasing with that of the GPS system, fulfils the requirements for the hydrographic surveys of harbours. To this end, an extensive experimental study on the maritime DGPS system, involving a total of nearly 3.5 million fixes, was conducted. Statistical analyses showed that when ensuring the HDOP values range from 0.8 to 1.4, the DGPS system can be used in hydrographic surveys of harbours

Application of an Autonomous/Unmanned Survey Vessel (ASV/USV) in Bathymetric Measurements

The accuracy of bathymetric maps, especially in the coastal zone, is very important from the point of view of safety of navigation and transport. Due to the continuous change in shape of the seabed, these maps are fast becoming outdated for precise navigation. Therefore, it is necessary to perform periodical bathymetric measurements to keep them updated on a current basis. At present, none of the institutions in Poland (maritime offices, Hydrographic Office of the Polish Navy) which are responsible for implementation of this type of measurements has at their disposal a hydrographic vessel capable of carrying out measurements for shallow waters (at depths below 1 m). This results in emergence of large areas for which no measurement data have been obtained and, consequently, the maps in the coastal zones are rather unreliable

Assessment of the Steering Precision of a UAV along the Flight Profiles Using a GNSS RTK Receiver

Photogrammetric surveys are increasingly being carried out using Unmanned Aerial Vehicles (UAV). Steering drones along the flight profiles is one of the main factors that determines the quality of the compiled photogrammetric products. The aim of this article is to present a methodology for performing and processing measurements, which are used in order to determine the accuracy of steering any drone along flight profiles. The study used a drone equipped with a Global Navigation Satellite System (GNSS) Real Time Kinematic (RTK) receiver. The measurements were performed on two routes which comprised parallel profiles distant from each other by 10 m and 20 m. The study was conducted under favourable meteorological conditions (windless and sunny weather) at three speeds (10 km/h, 20 km/h and 30 km/h). The cross track error (XTE), which is the distance between a UAV’s position and the flight profile, calculated transversely to the course, was adopted as the accuracy measure of steering a UAV along the flight profiles. Based on the results obtained, it must be concluded that the values of XTE measures for two representative routes are very similar and are not determined by the flight speed. The XTE68 measure (p = 0.68) ranged from 0.39 m to 1.00 m, while the XTE95 measure (p = 0.95) ranged from 0.60 m to 1.22 m. Moreover, analyses demonstrated that the statistical distribution of the XTE measure was most similar to the gamma and Weibull (3P) distributions

Assessment of the Steering Precision of a Hydrographic USV along Sounding Profiles Using a High-Precision GNSS RTK Receiver Supported Autopilot

Unmanned Surface Vehicles (USV) are increasingly used to perform numerous tasks connected with measurements in inland waters and seas. One of such target applications is hydrography, where traditional (manned) bathymetric measurements are increasingly often realized by unmanned surface vehicles. This pertains especially to restricted or hardly navigable waters, in which execution of hydrographic surveys with the use of USVs requires precise maneuvering. Bathymetric measurements should be realized in a way that makes it possible to determine the waterbody’s depth as precisely as possible, and this requires high-precision in navigating along planned sounding profiles. This paper presents research that aimed to determine the accuracy of unmanned surface vehicle steering in autonomous mode (with a Proportional-Integral-Derivative (PID) controller) along planned hydrographic profiles. During the measurements, a high-precision Global Navigation Satellite System (GNSS) Real Time Kinematic (RTK) positioning system based on a GNSS reference station network (positioning accuracy: 1–2 cm, p = 0.95) and a magnetic compass with the stability of course maintenance of 1°–3° Root Mean Square (RMS) were used. For the purpose of evaluating the accuracy of the vessel’s path following along sounding profiles, the cross track error (XTE) measure, i.e., the distance between an USV’s position and the hydrographic profile, calculated transversely to the course, was proposed. The tests were compared with earlier measurements taken by other unmanned surface vehicles, which followed the exact same profiles with the use of much simpler and low-cost multi-GNSS receiver (positioning accuracy: 2–2.5 m or better, p = 0.50), supported with a Fluxgate magnetic compass with a high course measurement accuracy of 0.3° (p = 0.50 at 30 m/s). The research has shown that despite the considerable difference in the positioning accuracy of both devices and incomparably different costs of both solutions, the authors proved that the use of the GNSS RTK positioning system, as opposed to a multi-GNSS system supported with a Fluxgate magnetic compass, influences the precision of USV following sounding profiles to an insignificant extent

Hydrographic Inspection Using a USV of a Harbour Bottom Deepened by the Periodic Actuation of SAR Vessel Propellers

In contrast to classic hydrographic cutters, unmanned surface vehicles, due to their size, ease of transport and the equipment installed, enable the performance of quick and cost-effective bottom inspections in various water areas. Thanks to their shallow draught and high manoeuvrability, hydrographic drones are capable of the bathymetric exploration of shallow waters such as harbours, hydrotechnical structures and the areas where classic naval vessels could encounter implementation difficulties. The aim of this paper is to demonstrate, using a selected practical example, the specific ability of an unmanned surface vehicle (USV) to carry out the urgent and immediate inspection of the bottom of a specific water area. The freedom to move between restricted areas, the ease of transport and the satisfactory quality of the surveys make hydrographic drones ideal tools for projects of this type. The referenced study produced a bathymetric map of a section of the seabed adjacent to the quay at which a Search and Rescue (SAR) vessel is moored and regularly, at its permanent fixed location, actuates its propellers. The effect of its propellers is the local deepening of the bottom in two places. The research showed a local decrease in the depth from 5.5 m to less than 7 m, which may threaten the stability of the quay structure. In addition, it was noted that the washed bottom material had been moved approximately 10 m from the quay, causing shallowing in two places and reducing the depth from 5.5 m to 4.7 m. This study demonstrated that the use of USVs for applications of this type is very effective in terms of the implementation time and is economically justified

A Method for The Assessing of Reliability Characteristics Relevant to an Assumed Position-Fixing Accuracy in Navigational Positioning Systems

This paper presents a method which makes it possible to determine reliability characteristics of navigational positioning systems, relevant to an assumed value of permissible error in position fixing. The method allows to calculate: availability , reliability as well as operation continuity of position fixing system for an assumed, determined on the basis of formal requirements - both worldwide and national, position-fixing accuracy. The proposed mathematical model allows to satisfy, by any navigational positioning system, not only requirements as to position-fixing accuracy of a given navigational application (for air , sea or land traffic) but also the remaining characteristics associated with technical serviceability of a system