by Jade Morton, Frank van Diggelen, Bradford Parkinson

After more than five years of hard work by 131 authors from 18 countries, “Position, Navigation, and Timing Technologies in the 21st Century” (“PNT21”) is finally ready to meet the readers. Published by Wiley-IEEE Press, and written by world-renowned experts, PNT21 offers uniquely comprehensive coverage of the latest developments in the field of PNT .

PNT21 is a two-volume set containing 64 chapters organized into six parts. Volume 1 focuses on satellite navigation systems, technologies, and applications. It starts with a historical perspective of GPS and other related PNT development. Vol 1 Part A consists of 12 chapters on fundamentals and latest developments of global and regional satellite navigation systems (GNSS and RNSS), the need for their coexistence and mutual benefits, signal quality monitoring, satellite orbit and time synchronization, and satellite- and ground-based augmentation systems that provide information to improve the accuracy of navigation solutions. Part B contains 13 chapters on recent progress in satellite navigation receiver technologies such as vector processing, assisted and high sensitivity GNSS, precise point positioning (PPP) and real time kinematic (RTK) systems, direct position estimation techniques, and GNSS antennas and array signal processing. Also: the challenges of multipath-rich urban environments, in handling spoofing and interference, and in ensuring PNT integrity. Part C finishes the volume with 8 chapters on satellite navigation for engineering and scientific applications. A review of global geodesy and reference frames set the stage for discussions on the broad field of geodetic sciences, followed by a chapter on GNSS-based time and frequency distribution. Three chapters are dedicated to severe weather, ionospheric effects, and hazardous event monitoring. Finally, comprehensive treatments of GNSS radio occultation and reflectometry are provided.

Volume 2 addresses PNT using alternative signals and sensors and integrated PNT technologies for consumer and commercial applications. An overview chapter provides the motivation and organization of the volume, followed by a chapter on nonlinear estimation methods which are often employed in navigation system modeling and sensor integration. Vol 2 Part D devotes 7 chapters to PNT from various radio signals-of-opportunity transmitted from sources on the ground, from aircraft, or from low Earth orbit (LEO) satellites. In Part E, there are 8 chapters covering a broad range of non-radio frequency sensors operating in passive and active modes to produce navigation solutions, including MEMS inertial sensors, advances in clock technologies, magnetometers, imaging, LiDAR, digital photogrammetry, and signals received from celestial bodies. A tutorial-style chapter on GNSS/INS integration methods is included in this Part E. Also included in Part E are chapters on the neuroscience of navigation and animal navigation. Finally, Part F presents a collection of contemporary PNT applications such as surveying and mobile mapping, precision agriculture, wearable systems, automated driving, train control, commercial unmanned aircraft systems, aviation, satellite orbit determination and formation flying, and navigation in the unique Arctic environment.

Because of the diverse authorship and topics covered in PNT21, the chapters were written in a variety of styles. Some offer high-level reviews of progress in specific subject areas, while others are tutorials. A few chapters include links to MatLab or Python example code as well as test data for readers who desire hands-on practice. The collective goal is to appeal to industry professionals, researchers, and academics involved with the science, engineering, and application of PNT technologies. A website (pnt21book.com) provides downloadable code examples, data, homework problems, select high-resolution figures, errata, and a way for readers to provide feedback.

If you wish to purchase this book through www.wiley.com you can use a discount code for 30% off - please use code: VBS10 between 21st October and 31st December 2020.

By Wim van der Heijden, FRIN

Twenty years ago, in 2000, the Automatic Identification System (AIS) became an obligation on board of ships falling under the IMO Safety of Life at Sea(SOLAS) Convention. It took fourteen years of discussions before the decision was taken to use AIS as the one and only identification system. A discussion, which started in the vessel traffic service (VTS) Committee of IALA to overcome the identification problems in VTS controlled areas. Here, in the VTS world, we see operators, sitting behind a radar screen, to advice a ship or pilot for its behavior. But radar shows positions; there is no capability to identify a ship. The correct identification of a radar target, representing an arriving or leaving ship, is crucial to address information to the proper ship. For this purpose we saw many years of trials in several parts of the world, based on many good ideas, ending with radar and radio transponders. However, due to a lack of standardization, each organization invented its own solution based on different technologies and procedures. It became clear that any form of active co-operation with the ships was needed for an unambiguous identification suitable in the entire world. In other words, an electronic box was needed to supply the operator with the requested information.

In some areas also the ship-to-ship identification was requested to improve safety of navigation. With the identity one could address another ship by VHF radio to communicate each other’s navigational behavior.

Two different methods were proposed over time to be used for identification, both based on radio technology. In the early 1990’s the first idea was to use the addressing tool for VHF radio (channel 70), the Digital Selective Calling (DSC). This should become a part of the mandatory Global Maritime Distress and Safety System (GMDSS) and soon available on all ships falling under the IMO SOLAS Regulations. However, there were some concerns raised with respect to the capacity and the disturbance of GMDSS which was intended to be used as an emergency system. In spite of this, some countries started implementation of DSC based transponders for ship identification with an idea to use an additional VHF channel to increase the capacity.

In the same period the development of mobile telephones started using Time Division Multiple Access (TDMA) technology. Mainly in Sweden ideas emerged to use this technology for ship identification as well. In a modified form because special facilities were needed for synchronization. The potential of this technology was promising, no limitations for the number of ships, continuously and not disturbing any other application in the VHF Maritime Mobile Band. But there were two dedicated VHF channels required for this idea.

The International Telecommunication Union (ITU) in the meantime allocated two VHF frequencies from the Maritime Mobile Band for identification purposes irrelevant which technology should be chosen (today known as AIS1 and AIS2).
After many considerations and discussions at IMO the solution was to go for the last one, ending with an adaption in the SOLAS Regulations in 2000 as said before.

That was twenty years ago, reason to memorize the history of AIS and to place it in its historic perspective. Because there was a lot before we get AIS, there were many decades with a number of experiments, sometimes successful, sometimes not, and it was a good idea to go further back in history. The outcome is a book, describing AIS in its historic perspective but, as reflected in the sub-title, a history of the identification of ships. This to show the reader how our ancestors did some form of identification in the early days.

The history did not end with the acceptation in SOLAS. This was a formal and legal step based on requirements. The development to make AIS a working system could start from here. This was mainly done at IALA where a special AIS Committee, in co-operation with other international bodies like IMO, ITU and IEC, further developed the proposed technology and formulated the different types of AIS stations. Also this entire process is, when we see this today, an historic development because this should be done in just two years time. The first ships carrying AIS were expected mid-2002 and the industry needed some time for production as well. Also this process, completed with the development of a lot of documentation, is described in this book. 

The book ends with a glance to the future. New developments based on the same technology are ongoing to modernize maritime communication.
The author, as an engineer, was part of this very interesting process, mainly in the period after 2000. The first period was more a political exercise.

If you are interested in this historical overview you can order your own copy of this book which is available through IALA as publisher using the following link:
https://www/iala-aism.org/product/ais-in-a-historic-perspective

The author, Wim van der Heijden, was engaged at the Netherlands Organization of Applied Scientific Research (TNO) from 1968 until 2005 after which he established ‘Ship Monitoring Consultancy’ for providing advice on maritime identification applications. Because of his involvement in the development of a predecessor of AIS, the Automatic Reporting and Identification System (ARIS) for the Netherlands Maritime Administration, he was asked to join the development of AIS within IALA and IEC on behalf of the Netherlands Administration. He was chair of the IALA AIS Technical Working Group from 2004 until 2010. This group was responsible for all AIS related questions in the IALA e-Navigation Committee. Wim is Honorary Member of IALA (2010), Fellow of the Royal Institute of Navigation (RIN) and member of the Netherlands Institute of Navigation (NIN).