How good a position can you get from GPS today in receive only mode?

You can download and store Open Street Map for individual states. Map data doesn't have to come in over the air. That's not the problem. It's enhancing GPS with cell phone tower data that's the problem. That requires a cell connection.

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ssl-3 2 hours ago | parent | next [-]

Resolution of less than 1 meter is normal with a decent view of the sky and a lack of interference. GPS itself is always receive-only on our end as consumers.

What problem are we trying to solve here? At this point in time, guided navigation with completely offline maps and GPS has already been a no-brainer off-the-shelf thing for decades.

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mmooss an hour ago | parent [-]

> GPS itself is always receive-only on our end as consumers.

AFAIK it's almost always enhanced by things cell tower data, wifi network data, and external data sources (besides the satellites). Look up GPS/GNSS enhancement and augmentation for the latter.

	▲	ssl-3 34 minutes ago \| parent [-]
		I mean exactly what I wrote: "GPS itself" means GPS, itself. Not GPS and WAAS. Not GPS and RTK. Not GPS + wifi + BT + cellular. I didn't mean any of those things, so I did not write any of those things. If the thing is more than GPS -- by itself -- then that's outside the scope of what I was referring to with the juxtaposition of the words "GPS" and "itself". (If a thing -- by itself -- can be better specified to be that way using concise phrasing, then I'm all ears.)

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garaetjjte 4 hours ago | parent | prev | next [-]

I don't think cell tower connection will give you any more precision, GNSS fix will be much more accurate. (within few meters)

You could get more accurate fix with RTK data, but I'm not sure if that's actually widely used. And in any case that doesn't require active communications either, you could get correction data from satellite broadcasts too.

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stackghost 5 hours ago | parent | prev | next [-]

>That requires a cell connection.

Technically it only requires an antenna that can listen on the LTE band (or even GSM). Trilaterating based on cell towers with a hackRF or other SDR is a fun exercise.

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themafia 4 hours ago | parent | prev [-]

GPS is exceedingly accurate compared to cellular signals on it's own. What it isn't is fast. So the "enhanced GPS" is mostly just proving satellite ephemerides so your GPS device can lock onto the overhead satellites faster.

If your device has zero GPS signal then you can get ~100m accuracy from the cellular signals alone. If your device doesn't have "enhanced GPS" then you can get ~1m accuracy from the GPS signals alone.

	▲	fc417fc802 4 hours ago \| parent [-]
		I think towers were historically already much more accurate than 100m in urban areas. Note that this changed with 5G beamforming. The new towers have a much better idea of where you are. (My understanding (thanks to other HN commenters) is that technically it's possible to do beamforming without deriving precise 3D coordinates but that this isn't how it's done in practice.)