3 ms·
It seems even better than that. My phone can tell me which side of a small road (2m accuracy) I am on 95% of the time. Maybe it uses a WiFi database and dead re
by dmurray 10y ago
It seems even better than that. My phone can tell me which side of a small road (2m accuracy) I am on 95% of the time. Maybe it uses a WiFi database and dead reckoning to improve on pure GPS.
- greglindahl 10y agoPhones generally use the WiFi database (plus cell tower info) to bootstrap GPS startup, but that's not useful for fine positioning.
- aargh_aargh 10y agoIt's called aGPS. https://en.wikipedia.org/wiki/Assisted_GPS https://en.wikipedia.org/wiki/Assisted_GPS
- TickleSteve 10y agoAGPS is designed to give a quicker Time-To-First-Fix (TTFF) but the accuracy is unchanged. The application here (driving) constrains the solution to 2D (i.e. known altitude from the map), and hence can since that variable is known quite accurately it can improve the accuracy of the other variables.
- 7952 10y agoReceivers tend to be built with augmentation systems. This uses a network of ground stations that measure the variation in the GPS signal and transmit corrections over an additional satellite. This helps the device account for atmospheric interference. https://en.wikipedia.org/wiki/Wide_Area_Augmentation_System https://en.wikipedia.org/wiki/Wide_Area_Augmentation_System
- kalleboo 10y agoYour phone also probably augments with the Russian GLONASS
- TickleSteve 10y agoGPS and location systems designed for driving will 'snap' to the correct side of the road. They're aware of what they're being used for and optimise for that. Similarly, because driving is 2D solution instead of 3D, the altitude will be used derived from the map, not the signal. Which is why GPS systems designed for driving are fundamentally not suitable for use in (say) planes which need a true 3D solution.