GPS seems fairly pedestrian now but my dad had one of the early Garmin models in the 90s and it was a kind of magic back then. Even outside of the actual location info, just seeing this thing in your hand listening to satellites up in space felt incredibly powerful. Later on you could get units compatible with Windows CE and mobile devices and it was easy to see why it would be a killer app on smartphones. It’s sad that the complexity and cleverness is all hidden now.
Yeah, navigating a big city meant finding a crossroads where you might be able to see a bit of sky. I used to wear a shoulder bag and attach the antenna to the strap to stay locked on.
Back then even light tree cover would sometimes trash the signal enough to lose position.
While modern GPS can get a position fix pretty quick, a cold start on standalone units can still take a while before it discovers enough satellites.
The crazy thing to me is now days my little tiny watch can do Wifi, Several Bluetooth protocols, 5G, NFC, Wireless charging and probably some other stuff I'm forgetting about. Oh and it supports a variety of global navigation satellite systems. Don't forget the high-res OLED display too. And the fact it is fully watertight.
All that while having a fairly impressive battery life.
> While modern GPS can get a position fix pretty quick
Can they? I have popular usb gps receivers and it still takes many minutes to get a lock on enough satellites to give accurate positioning. Given that it is dependent on things flying overhead in space, I don't think the receivers are where any "boot speed/signal lock" improvements can happen.
Mobile phones are no exception, they've just employed several tactics to make the perception seem as if it's instant.
They start with "course" location which is based of the geo data of the cell's ip address and vicinity to known wifi access ssids. They also know where you were at when the phone went into standby or was powered down, and can reasonably assume you haven't gone far away from that location without the accelerometer noticing movement of any kind (keep in mind most phones do not fully shutdown even when powered off). That's all a very good and pretty accurate starting point for when you fire up maps on your phone, and by the time it is a problem a "fine" gps signal is locked. And usually due to other system services (like network config, find my device, etc) firing up gps when you unlock your phone or some other privacy invading app running gps as a background task, there's usually a fine grained gps lock by the time you even open your maps app.
Modern GPS receivers are much faster. They can search for every possible satellite at every offset rapidly in parallel, meaning that they don't need the almanac in order to get a GPS lock quickly. They do still need the orbital data for each satellite being used, but that's transmitted by the satellite itself much more regularly than the almanac and mobile phones can generally speed things up even further by downloading a small amount of assistance data that contains orbits for all the satellites for the next day or so.
Take a look at the https://phyphox.org/ app for lower level access to the sensors on Android and iPhones. There is a GPS section that gives you coordinates but unfortunately doesn’t tell you about each satellite. The precision of other phone sensors seems even more amazing.
I mean, both GPS and WiFi was super exciting stuff in the early 2000s. There was a GPS magazine for GPS terminal enthusiasts (!). It's still sort of around: https://www.gpsworld.com/.
