Hacker News Reader

Comment by MilaM | Hacker News Reader

How is the positioning accuracy outdoors?

My iPhone 13 is rather disappointing in this regard. Even in my garden, with a clear sky, Maps.app will show my location at least 5 m off my actual position.

View on HN

5m is within the design spec of L1 GPS, so you’re getting it as designed. GPS was never designed to be mm level accurate. The new L5 frequency aims for 30cm accuracy.

> GPS was never designed to be mm level accurate

Kind of. Consumer/public GPS was never to be that accurate. Galileo for example, has the following accuracy: 1 metre (public), 1 cm (encrypted)

I'm sure the same applies to other systems too.

I don't really see the strategic importance of 1 meter Vs 1 cm positioning... Is the enemy missile going to miss the bunker because it hit 1 meter off? Or the enemy built their airport 1 meter wonky because they didn't have access to 1 cm level accuracy?

GPS might have been a military invention, but its uses reaches further out today. I think the purpose of Galileo's encrypted GPS is not to prevent military strikes against European nations, but to be able to offer more precision as a commercial service, making a profit.

Basically, companies who use GPS for measurements or what have you, can pay money and get access to improved accuracy.

But since GPS is a broadcast service, there is no way to offer encrypted service widely (ie. To a random app which pays for better GPS accuracy) without someone decapping/exploiting a chip in the phone and leaking the rolling encryption key via a web service for everyone.

Should be possible. Encrypted DVB-S providers can also lock/unlock single smartcards.

And it is pretty common that said smartcards get 'cracked', and then they have to reissue new cards to all viewers and switch to a new master crypto key. If even one legacy card remained in use, then attackers could use that card to dump the key used for the video stream and publish it online.

It's usually not that simple. Yes there is card sharing, but you need to have the card active for that. But card sharing is not "cracking" obviously. Also, you don't store the "master key" on the card, obviously.

Because the EU notionally (at least for now) is not a military alliance, Galileo does not have a military application. The slot where you would put a military encrypted mode instead has the "Public Regulated Service" to be used by authorized government bodies which might well in practice be military.

As the US found, in practice such services are largely useless, they sound cool, but in practice COTS (Commercial Off The Shelf) dominates. The $50 device you see on Amazon has better features than the $500 military product your supplier offers. When you ask the Amazon supplier can sell you 1-1000, with 48 hour delivery but your military supplier quotes 6-12 months with batches of 500.

Can the enemy jam your $50 Amazon special? Maybe. But in a hot war zone, unlike for an annoying neighbour, jamming isn't necessarily an effective strategy because it involves transmitting radio signals, which makes you a target.

The EU is a military alliance. There has been a mutual defense clause since 2009. So far it's not clear whether members will actually fulfill that obligation.

https://www.euronews.com/my-europe/2022/06/07/like-nato-the-...

Right.

1m vs 1cm is not a big deal for a rideshare driver. On the other hand, if two bridge spans meet in the middle and are 1m misaligned, that’s a huge problem.

It’s needed for things like site surveying and construction.

https://www.takeoffpros.com/2019/07/31/gps-surveying-explain...

Military stuff can be moving, sometimes quickly, so more accuracy at one point in the trajectory could result in more accuracy later on

Uhh, for hunter killer drones trying to minimize collateral damage using exclusively impact weapons (like what was used against the ISIS dude who was recently killed), that difference really, really matters.

It is possible on quite a few modern Android phones to access raw receiver data and do post-processing using a rinet file to get mm-level accuracy. It's a little over my head since this isn't my industry. One of Google's more obscure Android apps to be used with it: https://play.google.com/store/apps/details?id=com.google.and...

GPSTest also carries some logging functionality to do the same: https://github.com/barbeau/gpstest

Have you considered that the underlying map may be out? I remember (non-academic) researching this and looking through past Google Earth imagery and its about a 2 metre error.

When I compare Apple Maps and Google Maps, both show me in the same spot relative to the aerial imagery. Could of course be, that both apps are off. I think it's more likely it's the GPS accuracy.

I know that regular GPS is not super accurate. But my impression was, that chipsets which support Galileo in addition to GPS, would be more accurate than 5-10 m.

I live in a building. From my window I can see 28 satellites and I have a 2m precision radius.

Reply on news.ycombinator.com