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I have relied on gps with downloaded topo maps in areas where there is literally no cell reception. iPhone X using AllTrails fwiw, I feel like it must have a re

• jonah 5y ago
  Indeed it does have a true GPS satelite receiver. Actually, the iPhones are quite accurate. The iPhone 12 utilizes the GLONASS, Galileo, QZSS, and BeiDou constellations. Utilizing more satellites means determining location more quickly and returns better accuracy especially in marginal environments.
• johnwalkr 5y ago
  Have you ever used Garmin back in the day, or a USB GPS receiver? It can take a minute or so to get enough initial information to deduce a location at a low datarate. AGPS gets some or all of that information (I'm not sure) from another source, usually a cell phone network so that first location is deduced much faster. Modern phones have GPS receivers, but use AGPS. If a modern phone has no network signal, it will still get a GPS signal, it will just take longer to get the first location. Not to be confused with other technologies such as skyhook [2], which was used in iPhone 1 and other older devices to fuse radio signal strength, known wifi hotspot locations, etc as a kind of pseudo-GPS. It was only relevant for a few years. Wikipedia [1] has a nice short explanation. [1] https://en.wikipedia.org/wiki/Assisted_GNSS https://en.wikipedia.org/wiki/Assisted_GNSS [2] https://en.wikipedia.org/wiki/Skyhook_Wireless https://en.wikipedia.org/wiki/Skyhook_Wireless