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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

#111

Post by brokenmachine »

implements wrote: post #57
miahi wrote: post #11

Earlier quoted context omitted.

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.

I have a Garmin GPS watch for jogging, and it worked fine at 700kph during a flight. Really helped my monthly average running speed.

Re: We built a new GPS receiver engine

#114

Post by [deleted] »

azinman2 wrote: post #90

It seems like they did this for SpaceChain, which I had never heard of before. I read their information, taking about combining blockchain-technology and satellites, and I'm still very confused. Other than buzzwords, what is this actual business and why is the blockchain necessary here? dApps in Space? What? Why?

[deleted]

Re: We built a new GPS receiver engine

#115

Post by phicoh »

gorkish wrote: post #67
gsnedders wrote: post #16

Earlier quoted context omitted.

There's a few other restrictions as well as the 1000mph speed limit, as far as I'm aware. GPS is still slightly inaccurate in its publicly available form: there's a second frequency broadcasting an encrypted signal, and with both frequencies you can better account for variations in the ionosphere. Galileo I believe will shortly be the only system with worldwide coverage and publicly available multiple-frequency broad…

ITAR regulations restrict GPS for civilian use to a maximum altitude and maximum velocity, but this is solely a software limitation that is increasingly becoming less relevant. Although selective availability has been disabled for a very long time, even before SA was turned off it was easily possible to get a precision measurement by integrating over time as the SA error was pseudo-random. It is also possible to use…

I wonder how combining 2 GPS satellites with 2 Galileo satellites would work in a realtime setting.

As far as I know, GPS and Galileo have a different timebase. If you don't know the time difference, you can be way off.

Re: We built a new GPS receiver engine

#116

Post by andrewaylett »

epanchin wrote: post #6
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.

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.

It's a bit looser than that -- 1000 mph _and_ above 60,000 ft, while also being unmanned.

Apparently (that is, according to Wikipedia https://en.wikipedia.org/wiki/Global_Positioning_System#Rest... ) some systems implement the restriction as an "or" but the regs (https://web.archive.org/web/20080916123933/http://www.armsco... item 11 category II) don't require that.

Re: We built a new GPS receiver engine

#117

Post by eternauta3k »

0xffff2 wrote: post #91
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.

I'm a software engineer at NASA and it's an annoying fact of life for us every day. There's a huge overlap in the technology, we just have different applications. In fact, a huge percentage of our airplanes are aircraft military aircraft.

Doesn't NASA also work with spy satellites?

Re: We built a new GPS receiver engine

#119

Post by willis936 »

gsich wrote: post #118
PaulHoule wrote: post #103

Earlier quoted context omitted.

That's how long ago it was.

Yes. But what does location accuracy have in common with PPS accuracy besides that you need a fix?

Everything! :D GPS measures the time difference between multiple satellites that broadcast their location and time. You need very accurate timing information to have accurate location. Timing error that manifests itself in PPS would also manifest itself in location data.

Re: We built a new GPS receiver engine

#120

Post by zalo »

durkie wrote: post #61

Mostly off-topic here, but it seems like the best place to get an answer: several years ago in my lab at Georgia Tech, a technician I worked with said he had a friend who invented a device for doing celestial navigation, but that it 1) worked in the daytime somehow and 2) used digital technology so that it was more precise than a sextant / traditional celestial navigation. The technician was prone to a bit of exagger…

There's a recent presentation on one from NASA: https://core.ac.uk/download/pdf/286393566.pdf
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