GNSS

European GNSS Independent ATM Surveillance Satellite Constellation

The present invention provides a method for space-based air traffic surveillance. The GNSS independence distinguishes the proposed solution from the Automatic Dependent Surveillance-Broadcast (ADS-B) which is reporting the aircraft position based on the GNSS information. It uses uses MODE-S squitter radio signals that are recurrently transmitted by the aircraft and which contain a static 24- bit aircraft unique identifier (known as ICAO aircraft address) and other known bits (such as parity bits for the static address). This static content of the MODE-S signals is particularly important as it allows (satellite) receivers to significantly improve the signal detection as well as timing and carrier frequency estimation of the incoming signal, hence improving the accuracy of post-processing algorithms for geo-locating the aircraft.

The aircraft position is computed in real-time by applying known techniques such as multi-lateration techniques relying on Time difference of arrival (TDOA) or Frequency difference of Arrival (FDOA). Multiple satellites will receive each aircraft MODES-S squitter (broadcasting) signals either with some time delays or with relevant frequency difference due to Doppler, proportional to the distance of aircraft from each satellite, making it possible to calculate aircraft position geometrically, simply based on the difference in the time of arrival or the frequency Doppler shift of the signal received by multiple satellites.

In order to determine the position of the aircraft, at least four independent observations of the same MODE-S signal is required. However, a higher number of observations (if available) can be used to improve the accuracy of the position and resolve the dilution of precision caused by the geometrical location of satellites with respect to the target aircraft. www.esa.int

ESA selects Syntony receivers for LEO-PNT constellation demonstration

The European Space Agency (ESA) has selected Syntony GNSS to supply user demonstration receivers for its low-Earth orbit positioning, navigation and timing (LEO-PNT) project.

Led by Thales Alenia Space and funded by ESA, the first European LEO-PNT project aims to enhance PNT services from LEO. This initiative is expected to improve the accuracy and reliability of navigation systems. Syntony will provide its ground receivers, compatible with the new LEO/ PNT signals, as well as with GPS and Galileo systems. syntony-gnss.com

NHAI seeks global partners for GNSS-based toll collection system

Indian Highways Management Co. Ltd (IHMCL), which operates under the National Highways Authority of India (NHAI), has called for expressions of interest (EOI) to develop and implement a GNSS-based electronic toll collection (ETC) system.

Initially, NHAI plans to integrate the GNSS-based ETC system with the existing FASTag ecosystem through a hybrid model, with both RFID-based and GNSSbased ETC operating simultaneously.

Subsequently, dedicated GNSS lanes will be introduced at toll plazas, allowing vehicles with GNSS-based ETC to pass freely. Eventually, all lanes will convert to GNSS lanes, according to the statement. The invitation includes a detailed implementation plan and suggestions will be accepted till 22 July.

A GNSS-based ETC system is expected to streamline vehicle movement on National Highways, offering benefits such as barrier-free tolling, hassle-free riding experience, and distance-based charges, where users pay only for the stretch they ply on. This system aims to reduce toll collection inefficiencies, plug leakages and curb toll evasion. www.livemint.com