Jeff Geerling's blog post highlights Beidou Position System (BPS), China's independently developed global navigation satellite system, as a lesser-known alternative to GPS. He details its development, global coverage, and increasing accuracy, emphasizing its potential as a backup or even primary navigation system, particularly for those needing to operate independently of US-controlled infrastructure. Geerling shares his experience testing BPS receivers, noting its comparable performance to GPS in his basic experiments and the growing availability of BPS-compatible devices. He concludes by advocating for greater awareness of BPS as a viable option in the GNSS landscape.
GPS jamming and spoofing are increasing threats to aircraft navigation, with potentially dangerous consequences. A new type of atomic clock, much smaller and cheaper than existing ones, could provide a highly accurate backup navigation system, independent of vulnerable satellite signals. These chip-scale atomic clocks (CSACs), while not yet widespread, could be integrated into aircraft systems to maintain precise positioning and timing even when GPS signals are lost or compromised, significantly improving safety and resilience.
HN commenters discuss the plausibility and implications of GPS spoofing for aircraft. Several express skepticism that widespread, malicious spoofing is occurring, suggesting alternative explanations for reported incidents like multipath interference or pilot error. Some point out that reliance on GPS varies among aircraft and that existing systems can mitigate spoofing risks. The potential vulnerabilities of GPS are acknowledged, and the proposed atomic clock solution is discussed, with some questioning its cost-effectiveness and complexity compared to other mitigation strategies. Others suggest that focusing on improving the resilience of GPS itself might be a better approach. The possibility of state-sponsored spoofing is also raised, particularly in conflict zones.
NASA has successfully demonstrated the ability to receive GPS signals at the Moon, a first for navigating beyond Earth’s orbit. The Navigation Doppler Lidar for Space (NDLS) experiment aboard the Lunar Reconnaissance Orbiter (LRO) locked onto GPS signals and determined LRO’s position, paving the way for more reliable and autonomous navigation for future lunar missions. This achievement reduces reliance on Earth-based tracking and allows spacecraft to more accurately pinpoint their location, enabling more efficient and flexible operations in lunar orbit and beyond.
Several commenters on Hacker News expressed skepticism about the value of this achievement, questioning the practical applications and cost-effectiveness of using GPS around the Moon. Some suggested alternative navigation methods, such as star trackers or inertial systems, might be more suitable. Others pointed out the limitations of GPS accuracy at such distances, especially given the moon's unique gravitational environment. A few commenters highlighted the potential benefits, including simplified navigation for lunar missions and improved understanding of GPS signal behavior in extreme environments. Some debated the reasons behind NASA's pursuit of this technology, speculating about potential future applications like lunar infrastructure development or deep space navigation. There was also discussion about the technical challenges involved in acquiring and processing weak GPS signals at such a distance.
This paper explores the feasibility of using celestial navigation as a backup or primary navigation system for drones. Researchers developed an algorithm that identifies stars in daytime images captured by a drone-mounted camera, using a star catalog and sun position information. By matching observed star positions with known celestial coordinates, the algorithm estimates the drone's attitude. Experimental results using real-world flight data demonstrated the system's ability to determine attitude with reasonable accuracy, suggesting potential for celestial navigation as a reliable, independent navigation solution for drones, particularly in GPS-denied environments.
HN users discussed the practicality and novelty of the drone celestial navigation system described in the linked paper. Some questioned its robustness against cloud cover and the computational requirements for image processing on a drone. Others highlighted the potential for backup navigation in GPS-denied environments, particularly for military applications. Several commenters debated the actual novelty, pointing to existing star trackers and sextants used in maritime navigation, suggesting the drone implementation is more of an adaptation than a groundbreaking invention. The feasibility of achieving the claimed accuracy with the relatively small aperture of a drone-mounted camera was also a point of contention. Finally, there was discussion about alternative solutions like inertial navigation systems and the limitations of celestial navigation in certain environments, such as urban canyons.
Researchers have demonstrated a method for using smartphones' GPS receivers to map disturbances in the Earth's ionosphere. By analyzing data from a dense network of GPS-equipped phones during a solar storm, they successfully imaged ionospheric variations and travelling ionospheric disturbances (TIDs), particularly over San Francisco. This crowdsourced approach, leveraging the ubiquitous nature of smartphones, offers a cost-effective and globally distributed sensor network for monitoring space weather events and improving the accuracy of ionospheric models, which are crucial for technologies like navigation and communication.
HN users discuss the potential impact and feasibility of using smartphones to map the ionosphere. Some express skepticism about the accuracy and coverage achievable with consumer-grade hardware, particularly regarding the ability to measure electron density effectively. Others are more optimistic, highlighting the potential for a vast, distributed sensor network, particularly for studying transient ionospheric phenomena and improving GPS accuracy. Concerns about battery drain and data usage are raised, along with questions about the calibration and validation of the smartphone measurements. The discussion also touches on the technical challenges of separating ionospheric effects from other signal variations and the need for robust signal processing techniques. Several commenters express interest in participating in such a project, while others point to existing research in this area, including the use of software-defined radios.
Summary of Comments ( 111 )
https://news.ycombinator.com/item?id=43669308
HN commenters discuss the viability and practicality of BPS, noting it's largely theoretical and faces significant hurdles. Several point out the immense infrastructure investment required for terrestrial positioning systems like BPS, especially compared to the established satellite-based GPS. Some question the accuracy claims and highlight potential interference issues in dense urban environments. Others express skepticism about BPS's resistance to jamming and spoofing, crucial for critical infrastructure. A few comments mention Loran-C as a more mature terrestrial alternative, although it has its limitations. Overall, there's a consensus that while intriguing, BPS lacks the development and backing to become a serious competitor to GPS in the foreseeable future.
The Hacker News comments section for the post "BPS is a GPS alternative that nobody's heard of" (linking to Jeff Geerling's blog post about Beidou Position System) contains a robust discussion with various perspectives on the viability and implications of BPS.
Several commenters point out that BPS isn't exactly "nobody's heard of," particularly outside the US. Some users from Asian countries mention its widespread adoption in their regions for various applications, including ride-hailing services and personal navigation. They highlight that phones and devices often support both GPS and BPS concurrently, leading to improved accuracy and availability, especially in urban areas with potential GPS signal obstruction.
A recurring theme in the comments is the geopolitical aspect of BPS. Commenters discuss its role as a strategic alternative to the US-controlled GPS, offering nations more independence and potentially reducing reliance on American infrastructure. Some express concerns about the potential for data privacy issues and government surveillance with a system controlled by China. This leads to a discussion about the trade-offs between national security concerns and technological benefits.
Technical details of BPS are also discussed, with commenters mentioning its dual-frequency civilian signal and comparing its accuracy and coverage to GPS. Some users share their personal experiences using devices with BPS support, noting its performance in different environments. There's also a discussion about the integration of BPS into various devices and software platforms, with some commenters pointing out challenges in its adoption outside of China due to existing GPS infrastructure and industry standards.
The concept of combining multiple satellite navigation systems (GNSS) like GPS, BPS, Galileo, and GLONASS is brought up, with commenters emphasizing the benefits of increased accuracy and resilience by leveraging multiple constellations. This leads to a discussion of the future of global navigation and the potential for a more multi-polar system with less reliance on any single provider.
Finally, several comments focus on the blog post itself, with some users critiquing the author's characterization of BPS as "unknown" and suggesting that the title is misleading. Others appreciate the introduction to BPS and the subsequent discussion it generated. The comment section, overall, provides valuable insights into the current state and future potential of BPS, going beyond the initial premise of the blog post.