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We built a new GPS receiver engine

blog.coresemi.io

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Re: We built a new GPS receiver engine

#51

Post by londons_explore »

hjb wrote: post #47
loeg wrote: post #29

Earlier quoted context omitted.

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.

US law applies worldwide when it comes to this sort of stuff... You can bet if you started producing these chips and selling them to Iran, you would either be arrested and child porn found on your laptop, or have an 'accident'.

Re: We built a new GPS receiver engine

#52

Post by detaro »

jpm_sd wrote: post #48
detaro wrote: post #37

Earlier quoted context omitted.

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...

Thank you!

Re: We built a new GPS receiver engine

#53

Post by danisth »

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.

You set up the base station over a known point, and now your rover unit can give you cm level accuracy when it's within range of the base station (UHF radio range generally).

For a practical application, let's say you wanted to lay out crops for a small hobby farm. This can make getting your base station set up, because you might not care as much about absolute location, which would require finding a surveyed benchmark. Instead you put your base exactly on the corner of your plot, and after setting up a local grid system you can now exactly layout your farm according to your plan. You simply walk around with the rover unit and can get real time cm accurate "coordinates."

Re: We built a new GPS receiver engine

#54

Post by dmos62 »

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…

According to the wikipedia article, the tungsten rods in question would be 9 tons and would deliver an explosion equivalent to that of 11.5 tons of TNT. Considering the cost of getting it into orbit, this is only a good idea when the advantages of the delivery method outweigh that cost. The advantages of "rods from God" compared to ICBMS are that they're twice as fast and have different dynamics vs early warning systems or anti-ballistic systems.

By the way, checkout small kinetic projectiles bombardment https://en.wikipedia.org/wiki/Lazy_Dog_(bomb)

Re: We built a new GPS receiver engine

#55

Post by pjc50 »

willis936 wrote: post #14
epanchin wrote: post #6

Earlier quoted context omitted.

The speed limit in the US is 1000mph, else it’s a munition. I believe the US used to make their GPS slightly inaccurate, but this was done on the satellite side.

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

Anything's a munition if you drop it on someone's head from that height and speed.

Re: We built a new GPS receiver engine

#56

Post by londons_explore »

chc4 wrote: post #42
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.

GCJ-02 used to be a secret way to warp maps to make them less useful for military uses.

Now, the GCJ-02 is so well reverse engineered it's practically useless, and just introduces bugs in mapping software when different coordinate systems are used.

Re: We built a new GPS receiver engine

#57

Post by implements »

miahi wrote: post #11
PaulHoule wrote: post #2

For a drone to be affected by GPS speed limits it would have to be a hypersonic drone.

There are two limits: 60000ft and 1000 knots. Some manufacturers use "AND" between them, others use "OR"[1]. So you can have faster drones if you manage to stay below 60000 ft. [1] https://ukhas.org.uk/guides:gps_modules

Some manufacturers have imposed lower limits eg some older Garmin handhelds won’t display info at speeds over 90 mph, though they still maintained a fix. I believe it was to stop people using them in light aircraft.

Re: We built a new GPS receiver engine

#58

Post by cptskippy »

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.

It seems silly in today's world where anyone can roll a custom SoC and have it spun out by any number of Fabs over the weekend, but 30 years ago custom chips were pipe-dreams for all but the most advanced tech firms. The $2 microcontroller you use to turn your lamp on has more processing power than a desktop computer from the early 80s.

By putting artificial constraints on off-the-shelf GPS technology, it forced bad actors away from off-the-shelf technology and instead forced them to roll their own. This often meant an inferior product with potential compatibility issues and significant development time and costs.

The same thing is done with export controls. It seems silly today but in 2000 they were limiting where a Playstation 2 could be exported because at the time a beowulf cluster of PS2s would have been a powerful super computer for a country like Iran.

\* Missing words...

\\ The next generation of GPS doesn't have Selective Availability, presumably because today there's 3 alternatives to GPS out side of US control.

Re: We built a new GPS receiver engine

#59

Post by Avamander »

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.

Which receivers?

Re: We built a new GPS receiver engine

#60

Post by Rebelgecko »

willis936 wrote: post #14
epanchin wrote: post #6

Earlier quoted context omitted.

The speed limit in the US is 1000mph, else it’s a munition. I believe the US used to make their GPS slightly inaccurate, but this was done on the satellite side.

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

The majority of rockets that NASA has used throughout history are just modified nuclear missiles.
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