31–40 of 40 posts
Earlier quoted context omitted.
I like http://lea.hamradio.si/~s53mv/navsats/theory.html which has a different focus from the Ciechanowski article.
That's a 404 for me, but I think the site moved; this works: http://s53mv.s5tech.net/navsats/theory.html
The explanation about the spheres is slightly inaccurate. With one satellite, you won't get a circle on the earths surface, but a sphere. GPS is not constrained to earths surface (or the oblate spheroid approximating it), luckily.
Maybe i missed it, but the first step kinda skips over how the inital time is calculated - the cell can't know when the signal was transmitted without some prior time or location knowledge?
The signal that GPS satellites broadcast includes the current time, so knowing when the signal was transmitted is easy.
Knowing when it was received is harder, you would need a calibrated, synchronized clock. But you need to receive multiple signals to figure out your clock, so keep reading for that.
Do the satellites broadcast their own position, or is that all held in a database on your phone? Also why is it so draining on your battery to get GPS location, if it's just solving a simple calculation.
Do the satellites broadcast their own position, or is that all held in a database on your phone? Also why is it so draining on your battery to get GPS location, if it's just solving a simple calculation.
A slightly related question, if anyone knows - has phone GPS gotten worse in recent generations? More reliance on local wifi networks or something like that? I ask because I do a lot of backcountry hiking, camping, and foraging and rely on true GPS-only navigation. My most recent two phones (iphone and pixel) have noticeably worse GPS performance than previous phones, and I even changed OS ecosystems mostly hoping fo…
When disabling "Android intelligence" (iirc this is what runs WiFi location scanning in the background) from running in the background, the 7A would take much, MUCH longer to get a GPS lock on a window sill, vs the 3XL right next to it... as well as lower SNRs and fewer satellites seen and used.
I don't get it.
I love these incredibly simple and elegant classic technologies. GPS is one of the best. It seems like it would be incredibly complicated and mysterious, but it's actually quite straightforward. I'm working on a presentation now to explain how GPS works to second graders. If they understand it, I'll take some photos and do a write-up.
Wish they could solve the GPS altitude weakness Watches that use GPS for altitude are terribly inaccurate It is interesting to run the opensource GPSTEST app on a smartphone and watch the MSL "settle" over time but each sat seems to disagree * https://github.com/barbeau/gpstest btw watches are now getting THREE multi-band L1+L5 GPS chipsets, should help things quad-band GNSS coming soon too! * https://the5krunner.com…