“Seen & Heard” is a monthly feature of GPS World magazine, traveling the world to capture interesting and unusual news stories involving the GNSS/PNT industry.
POSITIONING UNDERGROUND
A “BeiDou positioning system for subways” began construction March 20 on the Beijing subway capital airport express line. The project will cover a 30-kilometer-long section of the express line, including five stations. To provide positioning, the BeiDou Navigation Satellite System (BDS) will be combined with 5G for indoor positioning or in areas where the satellite signals are blocked. The system will improve the positioning accuracy in subways to less than 2 meters, making it available for vehicle dispatching, passenger transport organization and emergency response. In addition, it allows passengers to use their phones to navigate and position in complex environments in subway stations through three-dimensional navigation.
THE SHAPE OF OCEAN WATER
The European Space Agency (ESA) investigated a technique to precisely measure sea-surface topography based on an idea submitted by the Institute for Space Studies of Catalonia (IEEC). The technique involves GNSS reflectometry — signals that have been reflected off of the sea surface at very low angles. The ESA-funded activity involved developing a GNSS receiver and setting up an experiment in the Balearic Islands to collect GNSS signals reflected off the sea surface. The team linked the coherence of the reflected signals to wave height and elevation angle of GNSS satellites. The team then processed the signals for optimized measurements of the shape of the sea surface, useful in applications such as ocean current forecasting, climate research, ship routing, cable laying and debris tracking.
CELLPHONE NETWORK DETECTS EARTHQUAKES
A paper published Feb. 9 in Earth, Planets and Space by Japanese Earth science researchers analyzed the potential of a dense network of GNSS receivers, installed at cellphone base stations, to monitor crustal deformation as an early warning indicator of seismic activity. Results showed that data from a cellphone network can rival the precision of data from a government-run GNSS receiver network, while providing more complete geographic coverage. Japanese cellphone carriers have constructed networks of GNSS receivers to improve locational information for such purposes as automated driving. The study examined the potential of a GNSS network built by SoftBank Corp. to play a role in monitoring crustal deformation.
ENDURANCE IN POLAR ICE
Researchers have discovered the remarkably well-preserved wreck of polar explorer Ernest Shackleton’s ship, Endurance, a century after it was swallowed up by Antarctic ice. A team of marine archaeologists, engineers and other scientists used an icebreaker ship and underwater drones to locate the wreck at the bottom of the Weddell Sea, near the Antarctica Peninsula. The ship is at a depth of 3,008 meters, 4 miles south of the position originally recorded by navigator Frank Worsley. The expedition team used two Saab autonomous underwater vehicles to explore in a pre-programmed search pattern. After the ship was located, technicians swapped out sonar equipment for a high-resolution camera and a laser-surveying device to make highly detailed scans of the site.
