Satellite Navigation
Fleeting- External reference: https://en.wikipedia.org/wiki/Satellite_navigation
satellite navigation system with global coverage is termed global navigation satellite system (GNSS)
2023[update], four global systems are operational: the United States’ Global Positioning System (GPS), Russia’s Global Navigation Satellite System (GLONASS), China’s BeiDou Navigation Satellite System,[1] and the European Union’s Galileo.[2]
How the A-GPS in your smartphone works, and whether Qualcomm is tracking you
- External reference: https://www.kaspersky.com/blog/gps-agps-supl-tracking-protection/48175/
How the A-GPS in your smartphone works, and whether Qualcomm is tracking you
device needs to know the exact location of the satellites to be able to perform the calculation, so it has to download the so-called almanac, which contains information about satellite positions and movement,
— https://www.kaspersky.com/blog/gps-agps-supl-tracking-protection/48175/
this takes between five and ten minutes to retrieve if downloading directly from satellite
— https://www.kaspersky.com/blog/gps-agps-supl-tracking-protection/48175/
can download the almanac from the internet within seconds via a technology called A-GPS (Assisted GPS).
— https://www.kaspersky.com/blog/gps-agps-supl-tracking-protection/48175/
As per the original specification, only actual satellite data available at the moment is transmitted, but several developers have added a weekly forecast of satellite positions to speed up the calculation of coordinates even if the receiver has no internet connection for days to come. The technology is known as the Predicted Satellite Data Service (PSDS), and the aforementioned Qualcomm service is the most impressive implementation to
— https://www.kaspersky.com/blog/gps-agps-supl-tracking-protection/48175/
problem with geopositioning using a satellite signal is that it may not be available indoors, so there are other ways of determining the location of a smartphone. The classic method from the nineties is to check which cellular base stations can be received at the current spot and to calculate the approximate location of the device by comparing their signal strength knowing the exact position of the stations.
— https://www.kaspersky.com/blog/gps-agps-supl-tracking-protection/48175/
Smartphones are also able to check for nearby Wi-Fi hotspots and determine their approximate location. This is typically enabled by centralized databases storing information about Wi-Fi access points and provided by specific services, such as Google Location Service.
— https://www.kaspersky.com/blog/gps-agps-supl-tracking-protection/48175/
All existing geopositioning methods are defined by the SUPL (Secure User Plane Location), a standard supported by mobile operators and smartphone, microchip and operating system developers. Any application that needs to know the user’s location gets it from the mobile operating system using the fastest and most accurate combination of methods currently available
— https://www.kaspersky.com/blog/gps-agps-supl-tracking-protection/48175/
Accessing SUPL services doesn’t have to result in a breach of user privacy, but in practice, data does often get leaked
— https://www.kaspersky.com/blog/gps-agps-supl-tracking-protection/48175/
data from an A-GPS request cannot be used for pinning down the user’s location. The almanac available from the server is the same anywhere on Earth — it’s the user’s device that calculates the location.
— https://www.kaspersky.com/blog/gps-agps-supl-tracking-protection/48175/
Assisted GNSS
- External reference: https://en.wikipedia.org/wiki/Assisted_GNSS
Assisted GNSS - Wikipedia
Assisted GNSS (A-GNSS) is a GNSS augmentation system that often significantly improves the startup performance—i.e., time-to-first-fix (TTFF)—of a global navigation satellite system (GNSS).
A-GNSS works by providing the necessary data to the device via a radio network instead of the slow satellite link, essentially “warming up” the receiver for a fix.
When applied to GPS, it is known as assisted GPS or augmented GPS (abbreviated generally as A-GPS and less commonly as aGPS). Other local names include A-GANSS for Galileo and A-Beidou for BeiDou.
data rate of the satellite signal is only 50 bit/s, so downloading orbital information like ephemerides and the almanac directly from satellites typically takes a long time, and if the satellite signals are lost during the acquisition of this information, it is discarded and the standalone system has to start from scratch
Some standalone GPS navigators used in poor conditions can’t fix a position because of satellite signal fracture and must wait for better satellite reception
regular GPS unit may need as long as 12.5 minutes (the time needed to download the GPS almanac and ephemerides) to resolve the problem and be able to provide a correct location.[2
A-GPS, the network operator deploys an A-GPS server, a cache server for GPS data. These A-GPS servers download the orbital information from the satellite and store it in the database. An A-GPS-capable device can connect to these servers and download this information using mobile-network radio bearers such as GSM, CDMA, WCDMA, LTE or even using other radio bearers such as Wi-Fi or LoRa
For billing purposes, network providers often count this as a data access, which can cost money, depending on the tariff.[3]
Notes linking here
- afterlife for my phones
- can programming be easier? (blog)
- check list setup old phone as gnss tracker