why did old (like 90s/2000s) GPS take up to 15 minutes to get a lock, in giant bulky units, but my running watch gets it in 15 seconds?
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Nowadays your devices download the GPS almanac (using GPS-A functionality), which usually requires an Internet connection.
Rather than having to “remember” where you were (and hoping you haven’t moved since you last had GPS turned on), it has to find you all over again from scratch and that initial lock can take a while to find.
GPS does transmit its own almanac but it’s slow to do so in order to be compatible.
With an up-to-date GPS almanac, which includes all the latest course corrections and orbit calculations for all the GPS units, it’s quicker to get a first-lock.
So if you have Internet, and a modern device, you can get first-lock faster.
Also, a tiny GPS chip now interacts with American GPS, Chinese Beidou, Russian GLONASS, European Galileo etc. GPS constellations all over the planet, so it’s far quicker to find 3 sats (basic 2D fix) or 4 sats (3D fix) much quicker.
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