Global Navigation Satellite Systems Engineering, Policy, and Design
In a nod to the usefulness of international enhanced Loran (eLoran) systems the U.S. Department OF Defense (DoD) in January began a search for companies able to supply some 50,000 eLoran receivers. Meanwhile a multi-agency team continues sketching out the structure of a potential U.S. eLoran system for federal officials weighing a relaunch of the program as a backup to GPS.
By Inside GNSS
TRANSNAV 2013 ParticipantsThe 11th International Conference on "Marine Navigation and Safety of Sea Transportation” TRANSNAV 2015 symposium will be held June 17-19, 2015 in Gdynia, Poland, a seaport and resort city on the south coast of the Baltic.
Online registration is open.
By Inside GNSS
Eugenia Acosta, an intern with Clearpath Robotics, unloads a Kingfisher unmanned vessel in preparation for a mission (top photo), the Kingfisher components and controller (bottom photo).“Our products are robotic research platforms,” says Clearpath’s Meghan Hennessey. “These can be configured and programmed so that our customers can explore their particular areas of interest without all the cost and troubleshooting involved in actually building robots themselves.”
Hennessey says Clearpath platforms — which include the all-terrain Husky, the larger, tractor-like Grizzly and the waterborne Kingfisher — can be thought of as project kits.
By Inside GNSS
Two European proposals to allow pseudolites in the protected frequencies used by GPS and Galileo could soon be adopted, creating a potential interference risk to GNSS receivers and hampering efforts to protect satellite navigation spectrum, experts say.
By Inside GNSS
The eDLoran receiver including antenna is mounted in a standard enclosure (14x14x10cm) for GPS-RTK equipment provided by AD Navigation (Norway)The Dutch Pilots Corporation and Reelektronika announced today (January 7, 2014) the successful development and test of an Enhanced Differential Loran (eDLoran) backup to GNSS in The Netherlands.
Trials at sea and in the Rotterdam Europort harbor area met the requirement for absolute accuracies in the five-meter range, according to Durk van Willigen, CEO of Reelektronika, and Wim van Buuren, Loodswezen’s information & communications technology (ICT) and innovation manager and board member.
By Inside GNSS
One in a series of NAV conferences sponsored by the Royal Institute of Navigation, this all-day event on February 21, 2013 will take place at Southampton Solent University Conference Center.
NAV-Maritime will focus on:
• Is ECDIS letting us down?
• The role of integrated navigation systems (INS) within e-navigation
• The increasing interest in unmanned vessels
The 2010 International Symposium on Certification of GNSS Systems and Services (CERGAL) will take place from April 28-29, 2010 in Rostock, on the Baltic Sea in the north of Germany.
The event includes a technical program and an industry exhibition.
By Inside GNSS
The 2010 CERGAL symposium will take place in the Baltic city of Rostock, in northern Germany, next April 28-29.
This year, the Symposium on Certification of GNSS Systems and Services will concentrate on maritime and inland waterways applications and GNSS testing infrastructure.
In addition to those topics, papers are invited on GNSS system aspects and aviation, road, rail and other special applications. Abstracts are due on November 30, 2009.
By Inside GNSS
Time Series and Power Spectrum of the L5 Demonstration SignalThe GPS IIR-20(M) satellite successfully transmitted for the first time a GPS signal in the L5 frequency band today (April 10), according to the U.S. Air Force operators of the Global Positioning System. L5, the third civil GPS signal, will eventually support safety-of-life applications for aviation and provide improved availability and accuracy to users.
By Inside GNSS
Q: What is the effect of GPS jamming on maritime safety?
A: Although GPS jamming incidents are relatively rare they can occur; and when they do, their impact can be severe.
The General Lighthouse Authorities of the United Kingdom and Ireland (GLAs) comprise the Commissioners of Irish Lights, the Commissioners of Northern Lighthouses and Trinity House, who between them provide aids to navigation (AtoNs) for the benefit of all mariners in British and Irish waters.
Q: What is the effect of GPS jamming on maritime safety?
A: Although GPS jamming incidents are relatively rare they can occur; and when they do, their impact can be severe.
The General Lighthouse Authorities of the United Kingdom and Ireland (GLAs) comprise the Commissioners of Irish Lights, the Commissioners of Northern Lighthouses and Trinity House, who between them provide aids to navigation (AtoNs) for the benefit of all mariners in British and Irish waters.
In order to investigate the effects of GPS jamming, whether by intentional or accidental means, the GLAs conducted a trial in 2008 on the effect of GPS denial on marine aids-to-navigation, and ship-borne and shore-based navigation and information systems.
Today’s mariners commonly use GPS enabled devices to navigate their vessels, however large, from port to port and berth to berth. The International Maritime Organization (IMO) mandates the carriage of electronic position-fixing systems by all vessels over 300 gross tons and those carrying passengers on an international voyage in accordance with the Safety of Life at Sea (SOLAS) convention.
The GPS position is often fed into other vessel systems, for example an electronic chart display and information system (ECDIS), the vessel’s automatic identification system (AIS), or a plotter.
The use of differential GPS (DGPS) is preferred; mariners improve their positioning accuracy and ensure integrity of their GPS derived position by using the large number of DGPS radiobeacons located around the world.
Although GPS receivers for navigation are commonplace and very conspicuous on the bridge, the use of GPS is often more inconspicuous in other AtoN and positioning devices. Examples include its use for providing position input to the onboard AIS transponder, as well as the digital selective calling (DSC) system, which has the capability to include the vessel’s position as part of a distress signal.
In addition to vessel-based systems, marine aids-to-navigation use GPS. AIS timeslots may be synchronized using GPS as a source of accurate time. AIS also provides AtoN position information based on GPS input. Synchronized lights use GPS as a common timing source, and differential GPS services provide accuracy and integrity to the mariner.
Therefore, GPS denial, whether intentional from malicious jamming or unintentional due to malfunctioning equipment such as television antennas, may affect safety both on the bridge and on-shore.
(For the rest of Alan Grant and Paul Williams’ answer to this question, please download the complete article using the pdf link above.)
Q: What are linear carrier phase combinations and what are the relevant considerations?
A: Linear carrier phase combinations are formed by adding or subtracting carrier phase measurements on two or more frequencies. Such combinations are used to improve the resulting measurement in some manner relative to the original measurements.
In this context, “improvement” usually implies removing/reducing certain errors so as to facilitate the ambiguity resolution process or increase the measurement (and, therefore, position) precision. We must note, however, that improvement in both areas is not possible and thus a design trade-off is required.
In this “solution,” we will discuss how linear carrier phase combinations are formed and the key considerations associated with this process. A discussion of some of the common GPS combinations is also provided.
Topics in the full article include Linear Combinations, Integer Nature of the Ambiguities, Magnitude of Errors in Units of Cycles, Magnitude of Errors in Units of Length.
Summary and Outlook
The analysis focuses on dual-frequency combinations. However, with the modernization of GPS and the upcoming launches of Galileo and Compass, multiple frequency combinations will be possible. Despite this, the considerations discussed in this article will still hold and can be used as a stepping stone for more advanced combinations and subsequent data processing.
(For the rest of Mark Petovello’s answer to this question, please download the complete article using the pdf link above.)
By Inside GNSS
One of 12 magnetograms recorded at Greenwich Observatory during the Great Geomagnetic Storm of 1859
1996 soccer game in the Midwest, (Rick Dikeman image)
Nouméa ground station after the flood
A pencil and a coffee cup show the size of NASA’s teeny tiny PhoneSat
Bonus Hotspot: Naro Tartaruga AUV
Pacific lamprey spawning (photo by Jeremy Monroe, Fresh Waters Illustrated)
“Return of the Bucentaurn to the Molo on Ascension Day”, by (Giovanni Antonio Canal) Canaletto
The U.S. Naval Observatory Alternate Master Clock at 2nd Space Operations Squadron, Schriever AFB in Colorado. This photo was taken in January, 2006 during the addition of a leap second. The USNO master clocks control GPS timing. They are accurate to within one second every 20 million years (Satellites are so picky! Humans, on the other hand, just want to know if we’re too late for lunch) USAF photo by A1C Jason Ridder. 
Detail of Compass/ BeiDou2 system diagram
Hotspot 6: Beluga A300 600ST
1. FOLLOW THAT PIZZA!
Huntsville, Alabama
√ Eleven Papa John’s pizza stores in Huntsville, Alabama equip their delivery drivers with handheld PNDs and use a mapping engine developed by startup company TrackMyPizza to give customers 15 second online updates on their pizza pie. You don’t even need to leave your laptop to look out the window.
The Nationwide Differential Global Positioning System (NDGPS) program has been salvaged from the political limbo in which it has resided for more than a year.
Following completion of an assessment by the U.S. Department of Transportation (DoT), the agency has decided to continue full NDGPS operations. Currently, 86 stations are operating with support from three federal agencies: the U.S. Coast Guard (USCG, 39 sites), the Army Corps of Engineers (9 site), and the DoT (38 sites operated and maintained by the USCG under contract).
By Glen Gibbons
