Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

We built a new GPS receiver engine

blog.coresemi.io

Post reply on HN
Print view View original

41–50 of 122 posts

Re: We built a new GPS receiver engine

#41

Post by michaelt »

Accujack wrote: post #30
cozzyd wrote: post #5

Affordable differential GPS would be a nice application... it just requires a fast way of synchronization between two devices (CW in the ISM band would probably work, for example).

RTK gps is better and quite affordable now. Look it up, you can use two receivers costing maybe $15 each for it.

Surely that little only gets you single-frequency receivers? So you'd be waiting around for 10 minutes to resolve ambiguities every time you got near a tree, bridge or building?

Or can you get multi-frequency receivers for that little these days?

Re: We built a new GPS receiver engine

#42

Post by chc4 »

sevenf0ur wrote: post #3

> Well, how about deliberate dilution of precision or intentionally limiting the speed the GPS chip can be used at? Is that a legal requirement or just done on request? I sort of chuckle whenever I hear of limitations like that being put in place as if someone that can construct an ICBM is going to be constrained by the GPS module.

China also has strict restrictions on GPS data, including requiring purposeful obfuscation of coordinates for their GCJ-02 geodetic datum, for national security purposes. They don't want accurate maps made.

Re: We built a new GPS receiver engine

#43

Post by umvi »

numpad0 wrote: post #40
umvi wrote: post #34

Earlier quoted context omitted.

Are you referring to Kinetic Bombardment?[0] Since kinetic energy increases with the square of velocity, if you can create a payload that can travel at hypersonic speeds (like a tungsten rod) without burning up then the amount of kinetic energy is in the tens of millions of joules. That's enough to destroy any single target, but doesn't have nearly the same destructive power as a nuke, which releases trillions of jou…

> That's enough to destroy any single target, but but that’s enough to destroy any single target! Like some bunkers.

True, but unless you have hundreds of them, I'm not sure if it's useful for MAD (i.e. replacement for nukes).

I suppose if you made the tungsten rods heavy enough and made made them travel fast enough you could get kinetic energy on par with small nukes, but the problem is it's highly directional (i.e. most of the energy is released underground and absorbed by the earth), unlike a nuke which can release all of its energy at once in an airburst 100 feet above a city.

It would be useful as a PGM in the arsenal, but probably not enough for MAD in an arms race. I could be wrong, though.

Re: We built a new GPS receiver engine

#44

Post by Piskvorrr »

umvi wrote: post #34
Piskvorrr wrote: post #18

Earlier quoted context omitted.

Well, both the Atlas and Soyuz (currently used by NASA and Roskosmos) were developed primarily for the U.S. and Soviet militaries as ICBM vehicles, the Space Race was something of a PR operation. After all, you don't really need to have an explosive payload: just dropping a heavy enough missile can be devastating.

Are you referring to Kinetic Bombardment?[0] Since kinetic energy increases with the square of velocity, if you can create a payload that can travel at hypersonic speeds (like a tungsten rod) without burning up then the amount of kinetic energy is in the tens of millions of joules. That's enough to destroy any single target, but doesn't have nearly the same destructive power as a nuke, which releases trillions of jou…

Sure, tungsten rods also work. What I meant was something far less sophisticated - "we don't care what specifically is hit, as long as it impacts in the general area." See e.g. the Qassam missiles, or similarly, the North Korean space program (or "space program"?) and Japan.

Re: We built a new GPS receiver engine

#45

Post by Piskvorrr »

umvi wrote: post #43
numpad0 wrote: post #40

Earlier quoted context omitted.

> That's enough to destroy any single target, but but that’s enough to destroy any single target! Like some bunkers.

True, but unless you have hundreds of them, I'm not sure if it's useful for MAD (i.e. replacement for nukes). I suppose if you made the tungsten rods heavy enough and made made them travel fast enough you could get kinetic energy on par with small nukes, but the problem is it's highly directional (i.e. most of the energy is released underground and absorbed by the earth), unlike a nuke which can release all of its en…

I thought that limiting the GPS from the top was to complicate making cheap missiles, something that might be used by rogue states or terrorists; for MAD, you probably wouldn't choose COTS equipment.

Re: We built a new GPS receiver engine

#46

Post by krapht »

willis936 wrote: post #13
cozzyd wrote: post #12

I am curious what timing precision they are achieving. You can easily get ~10 ns with cheapish GNSS modules.

10 ns is the quoted accuracy, but it’s not easy to verify that and it is very easy to mess up something at that timescale. If something is cheap, I’d be willing to bet their PPS output is not going to be 10 ns accurate. Most applications won’t tell the difference between 10 us and 10 ns accurate, but when you need it, you’ll know it.

I know lots of applications that could take advantage of 10 picosecond accuracy, if only it was feasible without spending hundreds of thousands of dollars.

Re: We built a new GPS receiver engine

#47

Post by hjb »

loeg wrote: post #29
jimhefferon wrote: post #4

Earlier quoted context omitted.

It was required. But that was gotten rid of by the Clinton administration. See https://www.gps.gov/systems/gps/modernization/sa/ .

The thing you're thinking of is true, but there are still speed limits on commercial GPS chips to prevent their use in missile guidance systems. TFA seems to be clearly flouting that law, so, good luck to them.

If you dig into their website, they appear to be based in Singapore and Japan. I've no idea if those countries have similar laws.

Re: We built a new GPS receiver engine

#48

Post by jpm_sd »

detaro wrote: post #37
Accujack wrote: post #30

Earlier quoted context omitted.

RTK gps is better and quite affordable now. Look it up, you can use two receivers costing maybe $15 each for it.

Do you happen to know a good introduction to how one would use it? I've looked at tools around it a few times, but always didn't find the point where it made "click" on how to actually do anything with them.

Yes! Check out this awesome blog.

https://deepsouthrobotics.com/2017/04/20/spilling-the-beans-...

https://deepsouthrobotics.com/2019/06/03/the-taming-of-the-u...

https://deepsouthrobotics.com/2019/05/23/piecing-together-an...

Re: We built a new GPS receiver engine

#49

Post by at_a_remove »

Accujack wrote: post #30
cozzyd wrote: post #5

Affordable differential GPS would be a nice application... it just requires a fast way of synchronization between two devices (CW in the ISM band would probably work, for example).

RTK gps is better and quite affordable now. Look it up, you can use two receivers costing maybe $15 each for it.

I've just started looking into RTK GPS. My state has a Trimble network that I might use. My application is, weirdly, something a lot like the waypoints of old Garmin GPS handhelds for hikers, only more accurate. I need to be able to lay down a series of points as I drive (perhaps around 30 mph or so) to map out a street network.

However, as I look around trying to find something I can just drop into my car and pull the data from (SD card? USB port?) later on, I haven't seen all of the RTK goodness trickle down yet into something relatively brain-dead and simple to use for my rather small case. I am definitely seeing kits and modules, and some stuff built into high-end drones, but it hasn't seemed to make its way down to my level yet and I am a little curious as to why (or if I am just not looking in the right place for the right thing).

Re: We built a new GPS receiver engine

#50

Post by Piskvorrr »

ISL wrote: post #24
willis936 wrote: post #14

Earlier quoted context omitted.

I find a bit of humor in imagining NASA rocket launches and atmospheric test vehicles being viewed, in some contexts, as a munition.

It is an unfortunate fact that many scientific endeavors involve technology that can have dual uses.

Starting with a rock. So, essentially, the whole tech tree.
Post reply on HN